Hunting Washington Forum

Equipment & Gear => Guns and Ammo => Topic started by: 7mmfan on July 19, 2014, 02:03:40 PM

Title: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 19, 2014, 02:03:40 PM: I have a handload that I shoot out of my 7mag, have been using it for years with great success. Have never had a need to shoot more than 150-200 yards, but recently have begun hunting more open ground and see the potential for 300-400 yard shots.

At 100 yards, I group consistany inside 1". At 200 I'm a little bigger than that.

Today I went to the range and shot at 300. I couldn't find a hole on paper. I felt very good about all my shots, no jerking/flinching, just solid squeeeeeze boom.

What could be happening between 100-300 that would cause me to not be on paper. My ballistics chart shows me only dropping about 4 inches between 100-300, so I highly doubt I was shooting low.

Load is a fairly hot load at 63gr IMR4831 with a 154gr Hornaday Interbond.

Guy at Kesselrings today told me he felt the bullet could be losing speed and stability, but I just don't think thats the case. Any thoughts?
Title: Re: 7 mag grouping issue, longish distance
Post by: bobcat on July 19, 2014, 02:11:31 PM: How big was your target? Was there any wind? Did you only shoot at 300 yards today?
Title: Re: 7 mag grouping issue, longish distance
Post by: jjhunter on July 19, 2014, 02:41:16 PM: Did you shoot a 100 or 200 yard target today?
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 19, 2014, 02:41:26 PM: Target was plenty large. 10" above and below and had same targets to either side so if it was drifting because of wind I would have hit. There was some wind, but my partner shooting his 7 mag at the same distance at the same time put together a perfectly normal group.

I shot at 100 to verify I was still on, and had a great 3 shot group. Did not shoot at 200 like I should have.
Title: Re: 7 mag grouping issue, longish distance
Post by: CAMPMEAT on July 19, 2014, 03:03:06 PM: My 308 did the same thing. Found out the scope was bad through process of elimination.
Title: Re: 7 mag grouping issue, longish distance
Post by: BOWHUNTER45 on July 19, 2014, 03:36:58 PM: Try that exact load with a 160 gr partition ...I wasted a lot of time and money trying to figure out my friend T3 in the 7mag ..so I bought some partitions and it ate them for breakfast ... :twocents:
Title: Re: 7 mag grouping issue, longish distance
Post by: big t on July 19, 2014, 03:47:38 PM: Try moving your target out 35, 40 yds at a time until you group starts to change and keep zeroing as you proceed out to you desired range of 300 or 400 yds. As long as your group is good at 100 I would start at that distance.
Make sure everything is tight (scope, rings etc.) I looked your load up, as close as I could get to it in my Nosler book and you should be good there.
I've been reloading since 1973. Doesn't make me an expert by any means however I believe you are shooting over your target as the slug is still climbing somewhat.
Hang in there you'll find a remedy for it. Get back to me and let me know how you do.
Title: Re: 7 mag grouping issue, longish distance
Post by: big t on July 19, 2014, 04:03:41 PM: Forgot to mention to make sure your scope is mounted square with the barrel. like this +
O
and not like this x.
O
Even a very slight off center and it will vary quite a bit at a longer distance.
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 19, 2014, 04:33:57 PM: I have been thinking a lot about a slightly heavier bullet and seeing if this improves grouping. I have shot 162gr SST's out of it and they did very well. I will double check the squareness of the scope and all fasteners. Thanks.
Title: Re: 7 mag grouping issue, longish distance
Post by: Karl Blanchard on July 19, 2014, 04:40:44 PM: Like has been stated before, make sure everything is tight and make sure your reticle is not canted. A few seemingly small issues like that won't show at 100 but magnify greatly at longer distances. Small variances with gun/load can make ballistic calculators pretty inaccurate. Also try shooting your buddies gun. Not saying it is you, but if you can't hit with his either then you could eliminate beating your head against the wall and spending a bunch of money trying to remedy your current rig. Good on you for hitting the range and practicing longer distances also! Lots of guys just print out a drop chart using the velocity off the back of the ammo box and think they are good to go. Prior planning and preparation prevents piss poor performance :chuckle:
Title: Re: 7 mag grouping issue, longish distance
Post by: Karl Blanchard on July 19, 2014, 04:43:23 PM: Quote from: 7mmfan on July 19, 2014, 04:33:57 PM
I have been thinking a lot about a slightly heavier bullet and seeing if this improves grouping. I have shot 162gr SST's out of it and they did very well. I will double check the squareness of the scope and all fasteners. Thanks.
Pretty good odds that the size of the slug isn't the issue. Those 154's have a good b.c. and the caliber itself is a great long range platform. I shot 150's out of mine and it was a tack driver at longer distances.
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 19, 2014, 04:51:32 PM: Great suggestion BLRman, way to make a guy think about the obvious answers to his problems! If I had not done a fair amount of long range shooting before with other firearms, I would definitely consider that. I have never run into this problem before where a seemingly accurate load and good group just disapeared at distance.
Title: Re: 7 mag grouping issue, longish distance
Post by: BUTTER on July 19, 2014, 04:55:29 PM: You really gave limited information on your grouping my 300 with factory ammo I have set at 2 inches high at one hundred its dead on at 200 and about six inches low at 300 I am guessing your dead on at a hundrerd?
Title: Re: 7 mag grouping issue, longish distance
Post by: Karl Blanchard on July 19, 2014, 05:17:14 PM: 24 or 26" tube? Have you ran the load through a chrony? Most reloading data for the 7mag is based off of a 26" tube. If you have a 24" pipe you should be subtracting about 35fps from your velocity. Also, do you know how high your reticle is from the center of the bore (sight height)? That can make a big difference in point of impact as well.
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 19, 2014, 05:58:20 PM: I'm sighted in 2" high at 100. Gun is a 26" barrel, don't know how high the reticle is above the center of the barrel, will have to check I guess
Title: Re: 7 mag grouping issue, longish distance
Post by: go4steelhd on July 19, 2014, 06:25:41 PM: Go buy a poster board at the dollar store. They are two for a buck. I think the are 36 by 30 inches. I'm assuming you are shooting off a bench. Try dry firing 5 times for every live round. Make sure you never move the cross hairs by pulling the trigger before you put a live round in. I feel with these two things your group will show up.
Title: Re: 7 mag grouping issue, longish distance
Post by: yorketransport on July 20, 2014, 02:16:17 PM: I'm pretty confident that you went under the target. With a 100 yard zero, your 154gr bullet at a pretty optimistic 3000 fps would drop more than 10.5". Your drop card likely says 4 MOA, not 4". Try holding a little high and I promise that you'll see an impact. :tup:

Andrew
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 26, 2014, 08:10:09 AM: I think I may have diagnosed the problem of this. I have been reloading with Grandpa this year. Its a great time, and I love spending time with him, but he is a... "fiddler". He likes to fiddle with things that don't need fiddled with. I found that my resizing die was not set properly so I was not getting a fulllength resize, and I also found that his calipers were off by almost a full .1". All my loads this year have had bullets seated a full .1" to deep, so I'm sure they are not leaving the gun consistently as they are not anywhere near in contact with the lands when chambered. This might explain OK accuracy at 100, and nonexistent accuracy at 300.

I've remedied the situation and I'm loading a few new rounds to go test drive.
Title: Re: 7 mag grouping issue, longish distance
Post by: mazama on July 26, 2014, 07:39:25 PM: Stopped at Winthrop range day before opener last year 100yds right on,stepped out 200 then 300,i was almost off target,ifound changing my rear rest from sandbag to a pillow if i remember right changed point of impact quite a bit.
Title: Re: 7 mag grouping issue, longish distance
Post by: RadSav on July 26, 2014, 08:17:57 PM: IMO, you don't take a subMOA round with a .535 BC at 100 & 200 yards and have it all the sudden fall apart at 300 yards. Even if the rifling was almost gone and the twist rate was messed up if it's subMOA at 100 & 200 it should be subMOA at 300 yards.

I've never gotten good groups with the InterBond so I do not have first hand knowledge on that bullet. But I do know that my loads for the 160 Accubond put me dang close to 12" low at 300 with a 100 yard zero. Muzzle velocity in the neighborhood of 2950.

Did you have the exact same rest on the 300 yard target as you had on the 100 & 200 yard target? Doesn't take much of a rise or drop in your cheek weld to misalign your eye to the scope. If you've got close to the same 12" drop as I do and only 10" from center to paper edge it wouldn't take much to lose paper sighted at 2" high at 100.
Title: Re: 7 mag grouping issue, longish distance
Post by: Biggerhammer on July 26, 2014, 09:24:49 PM: Quote from: mazama on July 26, 2014, 07:39:25 PM
Stopped at Winthrop range day before opener last year 100yds right on,stepped out 200 then 300,i was almost off target,ifound changing my rear rest from sandbag to a pillow if i remember right changed point of impact quite a bit.

Same as shooting with a bipod in the prone or on the bench. A rifle shot off a bipod will have a different point of impact depending if your shooting off a hard concrete type surface or dirt and it makes a big difference at distance.
Title: Re: 7 mag grouping issue, longish distance
Post by: Damnimissed on July 26, 2014, 11:45:02 PM: Quote from: Biggerhammer on July 26, 2014, 09:24:49 PM
Quote from: mazama on July 26, 2014, 07:39:25 PM
Stopped at Winthrop range day before opener last year 100yds right on,stepped out 200 then 300,i was almost off target,ifound changing my rear rest from sandbag to a pillow if i remember right changed point of impact quite a bit.

Same as shooting with a bipod in the prone or on the bench. A rifle shot off a bipod will have a different point of impact depending if your shooting off a hard concrete type surface or dirt and it makes a big difference at distance.

This may be a stupid question, but why is that?
Title: Re: 7 mag grouping issue, longish distance
Post by: RadSav on July 27, 2014, 01:53:43 AM: Quote from: Damnimissed on July 26, 2014, 11:45:02 PM
Quote from: Biggerhammer on July 26, 2014, 09:24:49 PM
Quote from: mazama on July 26, 2014, 07:39:25 PM
Stopped at Winthrop range day before opener last year 100yds right on,stepped out 200 then 300,i was almost off target,ifound changing my rear rest from sandbag to a pillow if i remember right changed point of impact quite a bit.

Same as shooting with a bipod in the prone or on the bench. A rifle shot off a bipod will have a different point of impact depending if your shooting off a hard concrete type surface or dirt and it makes a big difference at distance.

This may be a stupid question, but why is that?

Soft soil tends to absorb shock, gives a little and slows down the barrel lift enough to allow the bullet to leave the barrel before rising. Often on hard surfaces the shots will run high as the gun bounces or jumps. If you must shoot from a hard surface try to load forward into the bipod a little. Should feel like you are flexing the legs slightly.

If shooting without a bipod in the field I like to place my hand between a rock/log and the stock. Seems to reduce those high fliers. Of course I tend to forget that occasionally when an animal is in front of me. ;) May be one of the reasons I've hit a number of bear in the spine with round #1.

I think Biggerhammer shoots much larger guns than I do. Hopefully he will response to this one. Would be interesting to find how that might vari from my experience and training.
Title: Re: 7 mag grouping issue, longish distance
Post by: yorketransport on July 27, 2014, 08:06:56 AM: Every time you change something in the "system" you'll get a slightly different result. I had a 22-250 that would easily shoot 5 shot groups in the low .2"-.1" range with a specific front and rear rest. If I used a different rest the groups would double in size. The different rest changes the harmonics of the gun just like resting the barrel on a sand bag would.

I you switch from shooting off of a sandbag to shooting off of a bipod you are going to change how the gun moves. If you hold the rifle differently that will change it too. I don't think that a different rest would explain good groups at 100 and 200 yards, but a complete miss at 300.

Andrew
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on July 28, 2014, 07:24:50 AM: Learning all kinds of good stuff here. One thing that is clicking for me is that I always used to shoot this gun off of my pack, even when shooting at the range. I did this because I knew I would most likely be shooting off my pack if I needed a rest in the woods. This year I have not been doing that. Change of rest, change of impact/group.

Going to get out this week and see what kind of a difference this makes.

Thanks for all the insight, its been valuable so far.
Title: Re: 7 mag grouping issue, longish distance
Post by: fisheral87 on August 02, 2014, 09:05:20 AM: "Also try shooting your buddies gun."

BLR, I've just surpassed him as a marksman and he is having trouble coping. Sad really, blaming the equipment. :chuckle:
Title: Re: 7 mag grouping issue, longish distance
Post by: 7mmfan on August 02, 2014, 09:28:42 AM: Quote from: fisheral87 on August 02, 2014, 09:05:20 AM
"Also try shooting your buddies gun."

BLR, I've just surpassed him as a marksman and he is having trouble coping. Sad really, blaming the equipment. :chuckle:

pffft.
Title: Re: 7 mag grouping issue, longish distance
Post by: motg9_6 on August 02, 2014, 10:28:00 AM: check for copper fowling.
whats your trigger poundage? your wont notice a heavy trigger at 100 but once your start getting out there it makes a HUGE difference.
also the bullets may not like your gun at that range.
140 nosler accubond 68 rl19 does great outa mine but every gun is different
Title: Re: 7 mag grouping issue, longish distance
Post by: Don Fischer on August 02, 2014, 01:39:43 PM: You have a load that shoot's well at 100 and 200 yds but can't hit the paper at 300yds? What do you call good? Are you using a bench and bags?
Title: Re: 7 mag grouping issue, longish distance
Post by: birddogdad on August 12, 2014, 03:57:57 PM: IF you are 1moa at 1ooyd- 1inch and 2 inch group at 200 then off paper at 3oo this is a shooter issue not weapon, unless you are reticle adjusting from 2 to 300 for elevation. then you may have scope issue.