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Equipment & Gear => Guns and Ammo => Topic started by: bearpaw on February 03, 2017, 05:59:36 PM


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Title: 338-378 Weatherby Questions
Post by: bearpaw on February 03, 2017, 05:59:36 PM
Sportsman's Warehouse had some rifles marked down so I bought an Accumark 338-378. I also purchased two boxes of empty cases for handloading so I am wondering if anyone has developed a load for one of these rifles that they liked? I'm really curious what powder seems to work best for most people? THANKS for any info!
Title: Re: 338-378 Load Data
Post by: bearpaw on February 03, 2017, 06:02:20 PM
I've got a new VX-6, 3x18x50, that I could put on the rifle, but also thought about getting a Nightforce. The gun is still in the box, I don't know if it shoots well enough to justify a Nightforce?
Title: Re: 338-378 Load Data
Post by: JimmyHoffa on February 03, 2017, 06:12:04 PM
I find H-1000 to be best powder so far.  Retumbo has been fine too.
Title: Re: 338-378 Load Data
Post by: bearpaw on February 03, 2017, 06:14:06 PM
I find H-1000 to be best powder so far.  Retumbo has been fine too.

Are you getting the kind of accuracy you wanted? I know it's not a custom rifle but I'm hoping for pretty fair accuracy.
Title: Re: 338-378 Weatherby
Post by: kentrek on February 03, 2017, 06:24:46 PM
We did some work on with 300 grain bergers, don't Remember exactly load details but it was 1/3 minute load

Next time I go make bullets il get you the details if you're interested in running the big bergers
Title: Re: 338-378 Load Data
Post by: JimmyHoffa on February 03, 2017, 06:29:13 PM
I find H-1000 to be best powder so far.  Retumbo has been fine too.

Are you getting the kind of accuracy you wanted? I know it's not a custom rifle but I'm hoping for pretty fair accuracy.
It does alright.  For out of the box with load 1 just under an inch at 100 yds and load 2 right at an inch.  Even with the fluting, it heats up fast so at the 5th shot it begins to open.
load 1-200 gr Hornady Interlock, 9 1/2 M primer, 105.0 gr H-1000 , 3.71" avg of 3050 fps
load 2-250 gr Hornady Interlock, 215GM primers, 112.0 gr Retumbo, 3.73"  I get avg of 3070 fps

and like always with internet load data, bounce it off credible sites.
Title: Re: 338-378 Weatherby
Post by: bearpaw on February 03, 2017, 06:31:08 PM
We did some work on with 300 grain bergers, don't Remember exactly load details but it was 1/3 minute load

Next time I go make bullets il get you the details if you're interested in running the big bergers

I know a guy using 300 bergers in a 338 Edge with excellent results. I had planned on getting some to try.
Title: Re: 338-378 Weatherby
Post by: Come Get Some on February 03, 2017, 08:44:24 PM
A buddy of mine has this gun, 300 Gr Berger ,I will check to see but I think he uses 50 BMG. Great groups . Shoots clays at 550 all day with no effort. I will get the load tomorrow. Lots of damage from the 300 Berger.. We were in New Mexico, he shot a mule deer at a little over 600 yds. I watched the round in the Leica's . Looked like a tracer. Smoked the deer. Wasnt even close to a game.
Title: Re: 338-378 Weatherby
Post by: elkinrutdrivemenuts on February 03, 2017, 09:10:40 PM
Where? And how much for the rifle?
Title: Re: 338-378 Weatherby
Post by: Magnum_Willys on February 03, 2017, 09:19:35 PM
110 gr RL 25 with 225gr tsx most accurate and can use the full case capacity.  Kicks less good to 1000 yards and works with short 26" barrel.  Like any big 338 - especially 300 gr - group sizes dont grow as much after 200 yards once bullet settles down.  i.e. 1" group at 100 might be 3" group at 500. 

The new accumarks may be different but the old ones usually needed a bedding job and timney trigger to get moa/sub moa groups.  I expect new accumarks triggers can be lightened enough to work ? 

I read that this stuff works great for 300gr pills:  http://gibrass.com/gunpowder.html (http://gibrass.com/gunpowder.html)  order: WC-872 and load to H-870 DATA - max 109 gr.
Title: Re: 338-378 Weatherby
Post by: Taco280AI on February 03, 2017, 10:44:41 PM
How much did the rifle go for?
Title: Re: 338-378 Weatherby
Post by: Dan-o on February 03, 2017, 10:56:21 PM
How much did the rifle go for?

Yeah, inquiring minds want to know!
Title: Re: 338-378 Weatherby
Post by: b23 on February 03, 2017, 11:47:58 PM
If you're interested I still have two brand new boxes of Nosler Custom 338-378 ammo loaded with 225gr Accubonds.
Title: Re: 338-378 Weatherby
Post by: bearpaw on February 04, 2017, 03:39:07 AM
Thanks for all the info everyone!

110 gr RL 25 with 225gr tsx most accurate and can use the full case capacity.  Kicks less good to 1000 yards and works with short 26" barrel.  Like any big 338 - especially 300 gr - group sizes dont grow as much after 200 yards once bullet settles down.  i.e. 1" group at 100 might be 3" group at 500. 

The new accumarks may be different but the old ones usually needed a bedding job and timney trigger to get moa/sub moa groups.  I expect new accumarks triggers can be lightened enough to work ? 

I read that this stuff works great for 300gr pills:  http://gibrass.com/gunpowder.html (http://gibrass.com/gunpowder.html)  order: WC-872 and load to H-870 DATA - max 109 gr.

I've got some 225's and also some 160's and 185's I was going to test. The 160's were right at 3450 fps out of my 340, they should come out of the 338-378 like a varmint round. We've shot two bear and an elk with the 160's out of the 340, dropped them all, the elk was a little over 500 yds, bullet passed through all 3 animals. I'm not sure if the 338-378 will stabilize the 160's but plan to find out. There was very little recoil shooting them out of the 340, I would expect the same out of the 338-378 with such light bullets. I understand that if I'm shooting much farther than 500 I'll probably need to use heavier bullets. I'm hoping to shoot without the muzzle break but will probably have to use it for the heavier bullets. I'm really curious to see how much different these bullets shoot with and without the MB.

How much did the rifle go for?

Yeah, inquiring minds want to know!
Sportsmans Warehouse had Accumarks for $1695, I found this one in a Utah store when I was there hunting. That's the lowest price I've seen anywhere for a new 338-378 Accumark. I would imagine some of their other stores have the same deals.

If you're interested I still have two brand new boxes of Nosler Custom 338-378 ammo loaded with 225gr Accubonds.

Thanks for offering but I already have some weatherby brass and I want to use all the same brand of brass. Advertise it on here, I would think someone will want it.
Title: Re: 338-378 Weatherby
Post by: yorketransport on February 04, 2017, 10:20:56 AM
I worked with one for a little while for a guy and had good luck with H1000 and Retumbo for pretty much every bullet weight. They're a little too slow for the super light Barnes bullets, but still work pretty well. I was never really happy with how that particular gun shot with bullets under 225gr. The big cases get a little finicky with light bullets and I had more consistent loads with heavy weights. I've never played with Reloader 33 but it my be worth checking out as well. The best advice though is to only use the Federal 215 primers if possible. Regular large rifle magnum primers seem to struggle when you try to ignite over 100 grains of powder and you end up with random velocity swings or odd pressure signs.

I've got a new VX-6, 3x18x50, that I could put on the rifle, but also thought about getting a Nightforce. The gun is still in the box, I don't know if it shoots well enough to justify a Nightforce?

I think the VX-6 is perfect for a hunting gun. Other than the Nightforce SHV, their scopes are all huge and make a mid weight rifle too top heavy for my liking. Plus I still think the NXS is over rated. I've had a few and none of them really impressed me. The ATACR is a different story though!
Title: Re: 338-378 Weatherby
Post by: b23 on February 04, 2017, 05:11:27 PM
I suggest getting a very good rings and mount setup for your 338-378.  I had a NF NXS on my 338-378 Accumark and had a heii of a time keeping the scope from moving around.  After using two different sets of rings ended up putting a Near Mfg. 3 ring Alphamount on it and that did the trick because it never moved again.

Never messed with any bullets lighter than the 225's.  In my opinion the factory barrel is the weak link and is much to small of a profile for that big Weatherby 378 case.  Whenever I started to push the throttle down the groups would open up into the inches but if I kept all my loads very moderate it was about a 3/4-ish MOA gun.  The powders I used were H1000, Retumbo, and 7828ssc.  For the most part they all shot about the same size groups and accuracy loads were usually within 50 fps of each other.

If you're looking to do precision work, you could be a little disappointed but if minute of elk is good enough, you'll likely get along just fine with it.
Title: Re: 338-378 Weatherby
Post by: mountainman on February 04, 2017, 06:29:34 PM
Good hunting round👍
Can be a little disappointing as a "long range" prospect.
Mine loved 300 mk's and lighter accubonds, but suprisingly, nothing in between..
Title: Re: 338-378 Weatherby
Post by: yorketransport on February 04, 2017, 07:00:54 PM
I suggest getting a very good rings and mount setup for your 338-378.  I had a NF NXS on my 338-378 Accumark and had a heii of a time keeping the scope from moving around.  After using two different sets of rings ended up putting a Near Mfg. 3 ring Alphamount on it and that did the trick because it never moved again.


That's part of the problem with the NXS, it's so heavy that it want's to stay put while the rifle slides out from under it; stupid laws of inertia! :chuckle: Burris Signature rings are some of the best for holding a big heavy scope in place.
Title: Re: 338-378 Weatherby
Post by: b23 on February 05, 2017, 08:37:38 AM

That's part of the problem with the NXS, it's so heavy that it want's to stay put while the rifle slides out from under it; stupid laws of inertia! :chuckle: Burris Signature rings are some of the best for holding a big heavy scope in place.

Very true, NF scopes are heavy but just about all the good scopes are on the heavy side.
Title: Re: 338-378 Weatherby
Post by: BULLBLASTER on February 05, 2017, 09:30:12 AM
My cousin shoots a 338-378 with 300 grain Bergers. He isn't running them real fast at all at 2650 but they shoot very well there. They really have to be pushed into the case to fit in the mag. But even at that speed they are absolutely devastataing on game.
Title: Re: 338-378 Weatherby
Post by: Magnum_Willys on February 15, 2017, 09:35:38 PM
One interweb guy swears he gets 2950 fps with 116.5 gr RL33 and 300 gr smk with good accuracy. 
I'm going to start at 108 and work my way up and see what happens. 

Just Bought a box of these HSM's from Sniper Central as a baseline.  Can't believe they are that fast but we will see.....

3100 fps @ Muzzle
300gr Sierra Match King
Ballistic Coefficients
.768 @ 2300 fps and above
.760 between 2300 and 1800 fps
.750 @ 1800 fps and below
Title: Re: 338-378 Weatherby
Post by: b23 on February 16, 2017, 09:13:32 AM
One interweb guy swears he gets 2950 fps with 116.5 gr RL33 and 300 gr smk with good accuracy. 
I'm going to start at 108 and work my way up and see what happens. 

Just Bought a box of these HSM's from Sniper Central as a baseline.  Can't believe they are that fast but we will see.....

3100 fps @ Muzzle
300gr Sierra Match King
Ballistic Coefficients
.768 @ 2300 fps and above
.760 between 2300 and 1800 fps
.750 @ 1800 fps and below

I'd say 2950 w/RL33 is definitely doable but I don't know that your buddy will get very many reloads from his brass before he starts stretching primer pockets because his 116.5 of RL33 is a pretty hot load and 3100 would be a crazy hot load.
Title: Re: 338-378 Weatherby
Post by: Magnum_Willys on February 21, 2017, 09:58:55 AM
One interweb guy swears he gets 2950 fps with 116.5 gr RL33 and 300 gr smk with good accuracy. 
I'm going to start at 108 and work my way up and see what happens. 

Just Bought a box of these HSM's from Sniper Central as a baseline.  Can't believe they are that fast but we will see.....

3100 fps @ Muzzle
300gr Sierra Match King
Ballistic Coefficients
.768 @ 2300 fps and above
.760 between 2300 and 1800 fps
.750 @ 1800 fps and below

Update: Fired these HSM factory loads off and got 2900 fps on my magnetospeed.    Accumark 26" barrel.  I'm reading 100 fps lower than factory spec on weatherby ammo so these may be 3000 fps ammo .

Way faster than anything in the Nosler load table - I don't know why Nosler is so conservative - they show max load with RL33 of 108 grains at 2731 fps out of 26" barrel but show the Lapua at 2750 with 10 grains less powder and a 2" shorter barrel.  ????  Must be in case someone tries their loads with a gun without the weatherby headspace.
Title: Re: 338-378 Weatherby
Post by: b23 on February 21, 2017, 10:32:42 AM
Update: Fired these HSM factory loads off and got 2900 fps on my magnetospeed.    Accumark 26" barrel.  I'm reading 100 fps lower than factory spec on weatherby ammo so these may be 3000 fps ammo .

I'd trust what your Magnetospeed said long before I'd believe the velocity they claimed on the box.
Title: Re: 338-378 Weatherby
Post by: Magnum_Willys on February 21, 2017, 11:25:47 AM
Printed out a chart to show my son why he should switch from 225 gr to 300 grain for ELD hunting.  Out to 800 yards he could even use same turrets for both the drop is so close but the energy difference is huge.
300 gr SMK VS 225 Gr. Weatherby Tsx .  Actual tested velocities. 

Title: Re: 338-378 Weatherby
Post by: bearpaw on February 21, 2017, 07:44:07 PM
great info everyone  :tup:
Title: Re: 338-378 Weatherby
Post by: idaho guy on February 24, 2017, 12:34:45 PM
This may or may not help. I have loaded h50bmg with nosler accubond 180 gr in my 30-378 accumark and that was my most accurate round by far -recently I switched to retumbo and that has shot really good as well for long range   
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 10, 2017, 10:34:43 PM
What about reloading dies, I need to buy dies?
Which reloading dies do you guys prefer who have been reloading for the 338/378?
I read a comment here about 30/378 which is the same case: http://hunting-washington.com/smf/index.php/topic,25101.msg290151.html#msg290151
Title: Re: 338-378 Weatherby Questions
Post by: kentrek on March 10, 2017, 10:39:08 PM
You can always get by with less but I think you'll get your money's worth out of a redding competition set with the micrometer...check em out on you tube
Title: Re: 338-378 Weatherby Questions
Post by: JimmyHoffa on March 10, 2017, 10:42:06 PM
I just use the Hornady, full length is specific to .338-378, and the neck sizer is for any .338 cal.
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 10, 2017, 10:45:49 PM
All my other dies are rcbs and seem to have been pretty accurate, but I want fairly good performance from this gun, not sure if there would be a difference or not between loads from rcbs or redding?
Title: Re: 338-378 Weatherby Questions
Post by: yorketransport on March 11, 2017, 07:49:16 AM
I like the hornady dies. You can get a replacement micrometer adjustment for the seater die too if you wanted one. The micrometer is only a couple bucks and just screws on to the regular seating did.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on March 16, 2017, 08:19:34 PM
I got the Redding Deluxe Neck Die and Seater Die ($100) and ordered the $35 VLD micrometer for the seating die.   It doesn't have the interior sliding tube like the Competition Dies.  (Have those for my Lapua but $$$$)  Not sure it matters we will see.  Just started developing loads for it today:

338-378 Accumark, 26" Barrel w brake, 300 Grain Berger Elite Hunter - 3.880 COAL  (EDITED said 3.800)
RL33
106gr - 2588
110gr - 2669
112gr - 2773
114gr - 2823 @3.880    ( 2885 @ 3.800 )
116.5 - 2934

No pressure signs yet, will get to 3000 and then go back and search for accuracy.

Update - Gotta drop to 3.800 for proper magazine operation ( mag 3.86 but extractor without touchup is 3.800)

I don't think I'm going any higher than 114gr at 3.800 COAL with RL33 - not enough room with Bergers:
112 GR = 100% full
114 Gr = 102% 
116.5 = 104%  ( I don't like this much compression )

Going to Try SMK's which look better based on Yorke's terminal performance test.   Can get almost 3 more grains in case with SMK'S vs Bergers due to COAL limit. 

Update:
COAL 3.80 , RL33
300 Gr. SMK'S

114gr - 2870   
115gr - 2929      ( Too Hot !  slight ejector mark, slight stiff bolt )  100% full

Accuracy test next 112 to 114 grains with both SMK & Berger
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 16, 2017, 09:00:45 PM
Magnum_Willys that's really great info, thanks so much for posting, anxious to hear more about your dies.  :tup:

How's the recoil been so far, I haven't mounted a scope or shot my rifle yet, still trying to decide on scope and rings to use?

Yorke I'll check into the Hornady dies, do you think the loaded rounds will be much more accurate than RCBS loaded ammo? I've had good luck with RCBS so trying to determine whether to get something different or not?

I want to shoot a 300 grain bullet, has anyone been able to compare performance on game between the limited choices of bullets?
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on March 16, 2017, 09:17:09 PM
Mine has the factory break so with 225 grain factory loads it kicks quite a bit less than my unbraked 300 wm or 338 wm .  At max load with the 300 grain it is going to be almost as much as the unbraked 300 or 338 with synthetic stocks.    My buddy shoots his unbraked with factory 225 grains and says it not bad.  I haven't tried it.  I've heard 300 grains without a brake are not good. 

Title: Re: 338-378 Weatherby Questions
Post by: idaho guy on March 17, 2017, 10:29:48 AM
I have always used the rcbs dies on my 30-378(same case) and have never felt like I needed anything else the results have been great
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 17, 2017, 03:17:10 PM
Mine has the factory break so with 225 grain factory loads it kicks quite a bit less than my unbraked 300 wm or 338 wm .  At max load with the 300 grain it is going to be almost as much as the unbraked 300 or 338 with synthetic stocks.    My buddy shoots his unbraked with factory 225 grains and says it not bad.  I haven't tried it.  I've heard 300 grains without a brake are not good.

I have numerous magnum guns and none have a break, my 340 wtby didn't have a break and was just fine. I hate breaks, however, I too have heard the 300 gr bullets are brutal, not sure if I'm man enough try the 300's without the break?  :chuckle:
Title: Re: 338-378 Weatherby Questions
Post by: yorketransport on March 18, 2017, 09:05:57 PM

Yorke I'll check into the Hornady dies, do you think the loaded rounds will be much more accurate than RCBS loaded ammo? I've had good luck with RCBS so trying to determine whether to get something different or not?

I want to shoot a 300 grain bullet, has anyone been able to compare performance on game between the limited choices of bullets?

I like the Hornady dies better because of the elliptical expander on the sizing die and the floating "sleeve" on the seating dies. I don't know that the load more accurate ammo but I do think that they're an improvement over the RCBS dies, especially the bullet alignment on the hornady seating die.

I tested the 300gr SMK in my bullet trap and it performed great. I tried the 300gr OTM and 300gr Scenars but they didn't do well at low velocity; I'll try them again going a little faster. The 304gr Hammer bullets would be worth looking at too but they may not stabilize in your 1:10" twist barrel. I'll double check the length and see if they're too long or not.
Title: Re: 338-378 Weatherby Questions
Post by: mountainman on March 18, 2017, 09:58:31 PM
Mine has the factory break so with 225 grain factory loads it kicks quite a bit less than my unbraked 300 wm or 338 wm .  At max load with the 300 grain it is going to be almost as much as the unbraked 300 or 338 with synthetic stocks.    My buddy shoots his unbraked with factory 225 grains and says it not bad.  I haven't tried it.  I've heard 300 grains without a brake are not good.

I have numerous magnum guns and none have a break, my 340 wtby didn't have a break and was just fine. I hate breaks, however, I too have heard the 300 gr bullets are brutal, not sure if I'm man enough try the 300's without the break?  :chuckle:
Bet you'll be just fine👍
Just keep sessions to tolerable round counts. Hate breaks on hunting rifles also..
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 22, 2017, 07:15:57 PM

Yorke I'll check into the Hornady dies, do you think the loaded rounds will be much more accurate than RCBS loaded ammo? I've had good luck with RCBS so trying to determine whether to get something different or not?

I want to shoot a 300 grain bullet, has anyone been able to compare performance on game between the limited choices of bullets?

I like the Hornady dies better because of the elliptical expander on the sizing die and the floating "sleeve" on the seating dies. I don't know that the load more accurate ammo but I do think that they're an improvement over the RCBS dies, especially the bullet alignment on the hornady seating die.

I tested the 300gr SMK in my bullet trap and it performed great. I tried the 300gr OTM and 300gr Scenars but they didn't do well at low velocity; I'll try them again going a little faster. The 304gr Hammer bullets would be worth looking at too but they may not stabilize in your 1:10" twist barrel. I'll double check the length and see if they're too long or not.

Did the 300 SMK's expand good?
Title: Re: 338-378 Weatherby Questions
Post by: yorketransport on March 22, 2017, 08:39:21 PM

Did the 300 SMK's expand good?

The 300gr SMK  did great. I shot the 300gr Berger Hybrid, 300gr Scenar and the 300 SMK from the same gun, with the same load, at the same velocity and at the same range and this is what I got.
(http://i162.photobucket.com/albums/t260/collegekidandy/CE5237B8-EC73-4AED-8C0A-01016AE51A84.jpg) (http://s162.photobucket.com/user/collegekidandy/media/CE5237B8-EC73-4AED-8C0A-01016AE51A84.jpg.html)
(http://i162.photobucket.com/albums/t260/collegekidandy/C8EAEA68-CD69-465F-BC14-90A042E3D18C.jpg) (http://s162.photobucket.com/user/collegekidandy/media/C8EAEA68-CD69-465F-BC14-90A042E3D18C.jpg.html)
(http://i162.photobucket.com/albums/t260/collegekidandy/3FB9198E-ADCD-4A29-8283-72A1B0D0EBB3.jpg) (http://s162.photobucket.com/user/collegekidandy/media/3FB9198E-ADCD-4A29-8283-72A1B0D0EBB3.jpg.html)

These were all impacts velocities of about 1760 fps.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on March 22, 2017, 09:19:23 PM
SMK's have .088 less jump to the lands compared to bergers.  Not sure it matters in the Weatherby.  Seems to give the Berger another 50fps maybe velocity potential.   I'm hoping SMK's at 2850 are accurate in this rifle  - hope to test a batch next week.  Hard to Ignore Yorke's results !
Title: Re: 338-378 Weatherby Questions
Post by: mountainman on March 22, 2017, 10:10:05 PM
Seemed to work good on the 1 elk, 2 bears (1 coastal, one black) since they all didn't move at the shot..
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 23, 2017, 01:52:31 PM
great info, i've had good performance with other sierra bullets, i'll have to order some  :tup: :tup:

i wonder if they will hold together at higher velocities/close range shots?
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on March 30, 2017, 09:04:33 PM
Got a chance to shoot some more 300 gr SMK's today.  113 gr. RL 33 at an average of 2860 seemed to group the best ( was my starting load today) and only 22 fps max spread, 7fps average.  3.800 coal .   At  114 was starting to show a lil ejector mark and groups spread.  Not tack driving yet by any means need to keep playing with it.  Was hoping for something stable in the 2900's but didn't see it.   Have some more loads ready for next week.  So far it doesn't shoot the 300 gr smk nearly as well as the barnes 225 but we will see.   
Did wake the guys at the range up tho !
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 19, 2017, 07:45:25 PM
Shot some more today with 300gr  SMK's.  Same story, 113 gr RL33 was good @ 2850.   n570 was good at 107 @ 2855 fps @ .75 moa.

Ran numbers for Optimum Barrel Time (OBT) and checked with Quickload.  Optimum speed prediction was 2848 for RL33 and 2855 for n570 which is exactly what I found shooting.

That said - I'm not beating factory 225's in accuracy yet. 

Neck sized, 3.795 Coal, CCI Primers.

Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on April 20, 2017, 10:35:43 PM
Have you tried federal match grade magnum primers, not much more cost, I think they are hotter, you might pick up some speed or accuracy? If I ever get a chance that's what I plan to try.
Title: Re: 338-378 Weatherby Questions
Post by: JimmyHoffa on April 21, 2017, 07:33:33 AM
Have you tried federal match grade magnum primers, not much more cost, I think they are hotter, you might pick up some speed or accuracy? If I ever get a chance that's what I plan to try.
I've been using the 215 GMs.  They've been working fine.  Real consistent, though, the only others I have compared to are Rem 9 1/2 M and CCI Mag.  All of those worked fine too.
Title: Re: 338-378 Weatherby Questions
Post by: high country on April 21, 2017, 08:19:28 AM
Most of the guys over here that build big 338's see the least sd with h1000 and 300 gr pills. I'd never worry about chasing the lands on a wby because of the massive freebore. If you want to set up the best dies I'd consider a lee collet, or any bushing sizer that does not use an expander. Forster has the superior seater die....read up on their seater and it will make sense.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 21, 2017, 08:48:06 AM
Have you tried federal match grade magnum primers, not much more cost, I think they are hotter, you might pick up some speed or accuracy? If I ever get a chance that's what I plan to try.

That was my goto plan but can't get em. Saw a guy had 1000 on gun broker but wanted $250 for them  :yike:
Title: Re: 338-378 Weatherby Questions
Post by: high country on April 21, 2017, 09:55:19 AM
I've not been able to tell any difference between them and 250s other than 250s seat in loose pockets much better. I've got at least a thousand here if you want to try, but I'd just jump to 250s myself.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 30, 2017, 09:01:54 PM
Update: Pretty much settled in on these three for use with the 300 gr SMK's.  Hope to try the 285 ELD-x and the Nosler LRAB this summer when available.  The 225 Barnes TTSX may be the the winner out to 700 yards but haven't tested it yet.   

Speed in the 2850-2870 range seems to shoot best.  The RL33 can push it over 2900 but doesn't seem to help accuracy and kicks more.   

Running about 3/4 moa at 300 yards.  Not sure this factory barrel can do much better with the 3/8" jump to the lands with these.

Next to test for speed consistency among these 3 loads. 

Note: These loads are in fired brass, neck-sized only, 3.800 coal.  Full-sized brass takes somewhat less powder and Virgin new brass is much smaller and takes as much as 3 grains less for the same pressure.




Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on May 04, 2017, 12:50:04 PM
Well finally got a brick of 215M match primers. Wow much hotter than the Cci 250s in this gun. All my above loads are too hot with them but showing much less velocity spread. Gotta work some new loads up with these primers.
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on May 04, 2017, 08:17:14 PM
That's good to hear, I found them to be hotter too, I think there is more efficient powder burn because of that in the big cases! Anxious to hear your results!  :tup:
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on May 05, 2017, 07:57:34 PM
I tried the new Match primers out today - was windy so I only shot at 100 yards.  My first ladder test with RL33 started at 110 gr and worked up 1/2 grain at a time.  First 4 shots were in the same hole - .25 moa so I'm sold on these primers!  Gotta stretch out to 300 yards now to dial it in.  Much more predictable results with these in this big case. 

Had to drop 2 whole grains with Retumbo with these primers. 
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on May 06, 2017, 02:21:37 PM
Update:  Same story today.  110.5 gr RL33 is a tack driver.  215M Primers, 300smk are < .5 moa at 100, and < 2 inch groups at 300.   The 215M primer is very accurate with the RL33 at lower loads.  I think the CCI primers probably work better for Retumbo and N570 allowing more velocity with the 300 gr. bullet. 

Was hoping for 2900+ speed but will take 2800 and accurate for the moment.

Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on May 10, 2017, 05:14:46 PM
most excellent  :tup:
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on May 10, 2017, 07:31:34 PM
That plate on the lower left was 4 shots with 110, 110.5, 111, and 112 grains through basically one hole. Crazy. 

Overall two days, 6 different loads, new brass, necksized brass, full sized brass they all went into that same hole.   I guess they like that node.  :tup:
Title: Re: 338-378 Weatherby Questions
Post by: Biggerhammer on May 10, 2017, 08:56:06 PM
Exellent results. I have exclusively used Federal 210M & 215M primers for many years.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on June 29, 2017, 10:11:10 AM
Tried the Hornady 285 ELD's today at 525 Yards - scattered all over the place with both RL-33 and Retumbo in the loads I used with the 300 SMK's.  Velocity was 40 fps higher.   

I then shot a group with 300 SMK's and 112.3 gr RL-33 that was .7 moa at 525 Yards and would have been .4 moa if I hadn't pulled that one shot to the right that I knew immediately.  I'm sticking with the SMK's.

RL33 - 112.3 and Retumbo - 104.8 around 2820-2840 are my current loads for this rifle at 500+ yards.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on September 10, 2017, 12:16:38 PM
Son got a chance to shoot my reloads this morning.  5 shots in a 2.5" group at 500.   
300 gr. SMK, New Unprepped brass, 215m primer, 112.4 gr RL33.  3.795 oal
Just loaded brass right outa the box.  Doesn't get much easier than that.
2837-2852 fps.    Ave 2845.   
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on September 11, 2017, 08:45:53 AM
Son got a chance to shoot my reloads this morning.  5 shots in a 2.5" group at 500.   
300 gr. SMK, New Unprepped brass, 215m primer, 112.4 gr RL33.  3.795 oal
Just loaded brass right outa the box.  Doesn't get much easier than that.
2837-2852 fps.    Ave 2845.

That sounds great, how do you feel this bullet will do as a hunting bullet?
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on September 11, 2017, 10:42:29 AM
I chose it as best available 1000 yard elk bullet based on reviews from unbiased guys who see dozens to hundreds of elk shot annually and who shoot it themselves.  Yorks tests on here confirmed its a much better choice than bergers.  The only caveat is at less than 300 yards like other premium bullets it supposedly could perform erratically if shooting 3000 fps.   If I was worried about it I would shoot a factory 250 nosler out to 300 and jack it out and chamber the 300 smk for longer shots but I plan on using it at all ranges - hopefully we find out this Friday !
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on September 11, 2017, 11:03:21 AM
I chose it as best available 1000 yard elk bullet based on reviews from unbiased guys who see dozens to hundreds of elk shot annually and who shoot it themselves.  Yorks tests on here confirmed its a much better choice than bergers.  The only caveat is at less than 300 yards like other premium bullets it supposedly could perform erratically if shooting 3000 fps.   If I was worried about it I would shoot a factory 250 nosler out to 300 and jack it out and chamber the 300 smk for longer shots but I plan on using it at all ranges - hopefully we find out this Friday !

That makes sense, I've got some other 338 bullets I can use at closer ranges...  :tup:

I'm trying to find where to buy those redding dies you said you use? Cabelas don't carry them.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on September 11, 2017, 11:23:41 AM
https://www.midwayusa.com/338-378-weatherby-magnum/br?cid=8211 (https://www.midwayusa.com/338-378-weatherby-magnum/br?cid=8211)

I use the Lee Precision neck Die and the Redding  full length sizer die every 4 or 5 reloads as needed.  But for hunting I would just load factory new brass, then neck size - one box of brass should give you 60-80 shots at least till full size needed.   Lee precision neck and seating dies give least runout and are $160.

http://leeprecision.com/custom-collet-necksizing-large-series-die-set.html (http://leeprecision.com/custom-collet-necksizing-large-series-die-set.html)

I havent found a full length die that I like yet. Most shrink neck way down then expand it back up but not enough.  now that loads dialed in plan on just new brass and neck size till wont chamber. 
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on September 11, 2017, 11:59:38 AM
https://www.midwayusa.com/338-378-weatherby-magnum/br?cid=8211 (https://www.midwayusa.com/338-378-weatherby-magnum/br?cid=8211)

I use the Lee Precision neck Die and the Redding  full length sizer die every 4 or 5 reloads as needed.  But for hunting I would just load factory new brass, then neck size - one box of brass should give you 60-80 shots at least till full size needed.   Lee precision neck and seating dies give least runout and are $160.

http://leeprecision.com/custom-collet-necksizing-large-series-die-set.html (http://leeprecision.com/custom-collet-necksizing-large-series-die-set.html)

I havent found a full length die that I like yet. Most shrink neck way down then expand it back up but not enough.  now that loads dialed in plan on just new brass and neck size till wont chamber.

Thanks for the info, I've two boxes of new brass screaming "load me"!  :chuckle:

So you think I should get the Lee for seating bullets? If I understood correctly they want two fired brass and the bullet I want to load to custom make the die?

Are you putting any crimp on your loads?
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on September 11, 2017, 05:55:05 PM
I think the Hornady is good for seating, I use the redding with a micrometer top I have from another die on it which is nice.  The Lee works fine too.

I think Lee is the best for just neck sizing (only because you can't get a Redding bushing Die for this caliber)

But Just a Hornady neck and seating die for $80 should get some pretty good loads for you. 

If I was real particular ( I am) I would fire off a factory round (weatherby/norma brass) to get brass matching my chamber and send that with a 300 smk bullet to lee and have them make me a die set.  I know that will get you less than .001 runout typically if that matters. 
Title: Re: 338-378 Weatherby Questions
Post by: Ziptie on October 16, 2017, 08:48:29 PM
Great info!  I picked up a 338/378 acumark with hopes of using it as a 500 to 1000yds hunting rifle (I practice and have killed game at over 500 with my current set up).  I picked it up in a shop with a really really bad glass job, tossed the stock.  I fitted it with a new target style stock and gave it a proper glass/ free float.  I was planning on using 250gr pills but might jump up to 300 after this read.  Thanks again for posting there is not that much out there about this caliber. 

-Zip
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on October 16, 2017, 11:07:49 PM
Great info!  I picked up a 338/378 acumark with hopes of using it as a 500 to 1000yds hunting rifle (I practice and have killed game at over 500 with my current set up).  I picked it up in a shop with a really really bad glass job, tossed the stock.  I fitted it with a new target style stock and gave it a proper glass/ free float.  I was planning on using 250gr pills but might jump up to 300 after this read.  Thanks again for posting there is not that much out there about this caliber. 

-Zip

pickup an inexpensive scope level to mount on the scope.  makes a difference over 500 yards.  With a good bed job and trigger its just about finding a good load. 
Title: Re: 338-378 Weatherby Questions
Post by: Ziptie on November 08, 2017, 09:19:08 AM
Not to hi jack but I just got mine out to the range for the first time (picked it up as a barreled action in need of attention).  I glassed it into a new stock and tossed a 6-18x lue on it.  Factory 250gr partitions are at 1" at 100yds.  I am happy for its first time out, I have ordered dies and 300gr SMK, will pick up some Re 33 and start loading for it.  I still need to tune the trigger (scary light) it is hard to use. I think a clean trigger break will shave 1/4 to 3/8" off my groups with the factory 250's.  Thanks for all the great info!   
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on December 10, 2017, 09:09:53 AM
Did some shooting yesterday 8mph wind. Son brought his 338-378 with my custom 300 smk loads.   Cold bore, hadnt been fired since september.  First shot 1” low, 4” to the right rang the 10” steel at 994 yards.   I couldnt out shoot him with my custom Lapua.

Btw - 215m mag primers in stock at basspro as of yday. 
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on July 05, 2019, 09:56:26 AM
We finally got a new scope mounted on my 338/378 this spring and i'm going to make time to get this beast shooting. I really had a hard time deciding between Night Force, Leupold, and Huskemaw, I don't care for the busy reticles in Night Force and I'm already putting a 4x24 VX6 Leupold on my 6.5x300, plus my son is a dealer for Huskemaw so I decided to go with the Huskemaw 5x30. He has the 5x25 on his 30/378 and it does a great job for his intended purpose, so I'm going to try the 5x30 on this gun. If I decide it''s not what I want on this gun I can always get another scope for this gun and do some swapping around with another gun.

After considerable reading I just ordered one of those digital headspace gauges at http://www.larrywillis.com/, I'm anxious to see how it works, I'll try to remember to post again after I've used it. I'm hoping to keep the 338/378 brass as consistent as possible and I'll check some of the brass in other calibers I've been shooting for years.

I'm also ordering my 338/378 dies today so I can work up a load for this gun. I'm going to work up to the load posted by Magnum_Willys and see how that works in my gun. I have the same gun so I'm hoping for a similar load. I have the 300 gr SMK's, cases, and primers, I just need powder which should be available locally.
Title: Re: 338-378 Weatherby Questions
Post by: Matth on July 16, 2019, 08:34:35 AM
Any news on this yet, i just picked one up?
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on July 18, 2019, 11:46:35 PM
I think I have all my reloading stuff now, just haven't had time to do any reloads yet. I went with the hornady FL Die and Seater, and got their neck die and mircrometer for the seater die. I also got a concentricity tool and a headspace gauge. I've never needed these last two tools but figured they might benefit precision loading for this caliber and what I hope to do with it. Honestly I don't know if they are needed or not, but after doing some reading I decided I wanted to check that stuff too.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on October 30, 2019, 09:19:13 PM
Update:  My son used the 300 Gr SMK reloads this week in Idaho to down a nice bull at long range with his 338-378.  Rifle is bedded ( important!)  Best loads were factory new brass, 112.4 gr RL33.  He can hit 10" paper plate sized target at 1000 yards with this setup and did 3 times on this elk.   
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on March 18, 2020, 06:53:49 PM
Finished developing load for Uncles 338-378 today.  113.0 gr RL 33.  300 SMK. 
2860-2870 fps.   

Was also load developing Lapua with HBN so targets cluttered.  The 338-378 are shots in lower left quadrant at 960 Yards in 6 mph wind. 

Best is neck-sized,  dip necks in liquid graphite (auto parts spray can) seat to just under mag length.
Title: Re: 338-378 Weatherby Questions
Post by: bearpaw on March 18, 2020, 07:11:12 PM
 :yeah: That's some good shooting  :tup:
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 20, 2020, 09:08:33 AM
Finished tuning Uncles rifle today.  Had a little throat growth so bumped up to 113.5 RL33.
Cold bore at 966 yards.   2850-2870 node. 

Title: Re: 338-378 Weatherby Questions
Post by: Matth on April 20, 2020, 01:26:29 PM
Nice, i shoot just like that in my dreams.
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 20, 2020, 01:37:04 PM
Yea my uncles pretty stoked.   Hope new barrel on my Lapua will do as well. 
Title: Re: 338-378 Weatherby Questions
Post by: Matth on April 20, 2020, 02:05:23 PM
Does your uncles rifle have the factory barrel on it? My 340 shoots lights out with factory, barrel a bedding job, and trigger work.
The 338-378 is bone stock still, and shoots just like the 340 used to.
How many rounds did the HCA tube have prior to needing a new one?
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 20, 2020, 03:00:55 PM
Yea factory barrel but quality bedding job and reworked trigger plus load development. 

Got about 900 rounds I think on Lapua.  Pushed it pretty hard and rushed cooling a few times.   30” proofs were in stock for $700 so decided to try that.   Like to shoot 2860.   Prob shuda gone Norma but Lapua’s done well.

Title: Re: 338-378 Weatherby Questions
Post by: Matth on April 20, 2020, 03:19:03 PM
Yea factory barrel but quality bedding job and reworked trigger plus load development. 

Got about 900 rounds I think on Lapua.  Pushed it pretty hard and rushed cooling a few times.   30” proofs were in stock for $700 so decided to try that.   Like to shoot 2860.   Prob shuda gone Norma but Lapua’s done well.

You and Mike almost had me talked into an HCA built Norma a while ago then i got the Weatherby to shoot. Now i have another MarkV to make shooy
Title: Re: 338-378 Weatherby Questions
Post by: Magnum_Willys on April 20, 2020, 03:56:20 PM
I bedded uncle’s and son’s 378-378’s and they both shoot at least as well as my custom Lapua, darn it.   I’m tweaking my bullet jump  .005- .020 and there’s is like 1/4 inch and kickin my tail.  Heh.  I think the older 338-378's had Bartlein Barrels.    At shorter ranges my Lapua is a little tighter but not by much.    Mite build a 300 wsm with 215 bergers for lighter plinking to a 1000. 
Title: Re: 338-378 Weatherby Questions
Post by: Matth on April 20, 2020, 08:48:32 PM
Lighter plinking to a thousand Ha. Growing up hunting on the west side those are dirty words, but it is fun. When i talk to the rest of the family about it they think i'm crazy. Steven hunts with a muzzy so he just laughs at me. I hunt with a bow in Oregon so i'm super weird says my dad. I am fairly sure your correct about the barrels, my older 340 was easier to get shooting than the new 338-378, even prior to the aftermarket work.
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