338-378 Weatherby Questions

[b23]

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.

[mountainman]

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..

[yorketransport]

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! Burris Signature rings are some of the best for holding a big heavy scope in place.

[b23]

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! 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.

[BULLBLASTER]

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.

[Magnum_Willys]

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

[b23]

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.

[Magnum_Willys]

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.

[b23]

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.

[Magnum_Willys]

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. 

[bearpaw]

great info everyone 

[idaho guy]

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   

[bearpaw]

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

[kentrek]

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

[JimmyHoffa]

I just use the Hornady, full length is specific to .338-378, and the neck sizer is for any .338 cal.