Weird accuracy issues

Adlerkopf

Private
Minuteman
Apr 3, 2019
3
2
Hello everyone!
I find myself in a very strange situation (at least for me). My rifle went from 0.7" groups with Federal GMM to 3-5" groups with other match rounds which I bought when I ran out of GMM. At first I thought it was an issue with ammo QC, but now that it happened again with a different brand I'm not sure what to think anymore.
For the record, I live in Chile, South America, where .308 match ammo costs around 3 to 4 USD per round, and there is not much variety to choose from at any given time. We must buy whatever we can find, and because of local laws I can't sell this ammo to someone else if my rifle doesn't like it.
I'm going to describe this rifle's life so maybe someone can find a probable cause.

All group sizes mentioned here are 5 rounds, shot at 100yards, either prone or from a bench, rested on a bipod or a sandbag. I don't really shoot for groups too often, only now and then just to test new ammo and to check everything is funcioning properly. I shoot mostly at longer ranges (300 to 900 yards), at steel targets 2-3moa in size.

The rifle is a .308 Remington 700P with 5R rifling, 1/10 twist, made in 2018. It has a Sig Sauer Tango 4 Scope on top and a Harris Bipod. I am it's first and only owner.
The first rounds I fed this rifle were Winchester 168gr SMK. Groups started at 1" and got to 0.8" for the last few (I only bought 40 rounds of these).
I tried cheaper ammo with mediocre results as could be expected (3.5" with 150gr bulk ammo, and 1.5" with some hunting 180gr rounds).
Then I bought 200 rds of Federal GMM in 175gr. I got 0.7" groups consistently, and perfect long range performance.
At some point I added a large muzzle brake that I got from another shooter and I suspect it is a knockoff, but it performed really well without any accuracy issues that I could notice.
Running low and unable to find any more of the Federal GMM, I bought 300 rds of Remington Premier Match 175gr SMK, confident in the performance that SMK rounds had had in my rifle. They performed really well in the beginning, with consistent 0.6" to 0.7" groups.
Then I got a KRG Bravo stock, which I installed myself carefully following the instructions.
Some time later, after several boxes of the Remington ammo I started getting lots of fliers and some groups opened up to 5". I would sometimes get 2 or 3 rounds to land perfectly and a couple fliers, other times I would get all 5 rounds all over the place.
I cleaned the barrel, re torqued all screws, tested without the muzzle brake, gave it to other shooters to test, from the bipod and from sandbags, but thr groups still looked like shotgun patterns.
Then I found a partial box of GMM that I still had lying around, and shot a 0.7" group with them.
After this, of course I suspected the quality of the Remington ammo, and inspected the boxes and expended cases. I found out that I have 2 different lots, one from 2016 which I already expended, and one from 2019 from wich I still have 8 boxes. I found several cracked cases in the 2019 lot boxes (unfired rounds, with a crack in the neck where the bullet sits).
Convinced at this point that it was an ammo issue, I bought 300rds of Hornady Superformance ELD Match 168gr, which AFAIK have good reputation for PRS and NRL competition purposes. I tried them last saturday just before a match, and to my dismay I got the same result, 5" groups without any apparent reason (about half of the shots hit where intended and made a decent group, and the other half ended up 2 or 3 iches away). I ended up shooting the match with the Remington ammo, after inspecting and discarding all rounds with cracked cases. The results of course where not satisfactory, I missed lots of easy shots, and the corrections made upon observed impacts didn't get me any closer to hitting the target.
Later I talked with other shooters, who said they had (or heard of) the same issues with Hornady Superformance ammo (allegedly caused by their extreme speed, around 2800fps) and recommended getting rid of it, or at least rebuilding them in a press (I don't have a press, nor access to one).

Should I assume it's the ammo fault again? Maybe my rifle just doesn't like it? Maybe there is something else in the rifle that's acting funny?

Possible solutions I'm considering:
1) Test more kinds of ammo (really hard to do here as I expained earlier)
2) Try the Erik Cortina EC Tuner/Brake and see if I get good results with the Hornady ammo
3) Go back to the original stock
4) Try it without the brake
5) Change the scope for a Leupold Mk5
6) Reset everything to factory specs and build the rifle again starting from the scope.

I should probably do all of them, but I'm kind of hoping there is an easy fix that I just didn't see and will solve the problem without spending a fortune on additional accesories and boxes of ammo just for group testing.

Thanks in advance for any help you can provide.

Regards,

Stefan
 
Last edited:

Zuul

Green Banana Samoan
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Jan 18, 2014
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Kona, Hawaii
I had the same issue, my AI AT with a 308 barrel runs like a raped ape with FGM, Hornady and Nosler factory loads suck hairy goat ass. Why, I have no idea. Maybe Hornady and Nosler really hate the English.
 

ShtrRdy

Gunny Sergeant
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  • Sep 17, 2011
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    Oh, Stefan, I'm sorry to hear of your troubles. When you found the few rounds of FGMM, was that recently? From most of your story I was going to recommend checking scope/rings/base and action-to-stock. But if you recently were able to shoot a few rounds of FGMM well then that seems to tell us the rifle is okay.

    If it is possible for you to purchase a reloading press and scale I think that would be very useful for you. You could then either buy factory loaded ammo and make changes in powder charge weight and/or seating depth OR buy reloading components and build ammo that works well in your rifle.
     
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    Lowholer

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    Minuteman
    Apr 19, 2017
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    You will continue to have this problem with factory ammo.Its not so much the ammo is bad its just is not in the sweet spot (node) that your rifle likes.Re loading is not hard to learn and the pay off at the end of a range day will leave you smiling! Not to mention the huge save up some expensive factory ammo money and go get a rock chucker starter kit.cost savings. Are you allowed to reload in chile? Do you have strict gun regulations?
    Good luck with your dilemma
     
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    ColdBore007

    Private
    Full Member
    Minuteman
    Jan 2, 2011
    56
    18
    Alaska
    Sounds like your rifle likes the 175gr Matchkings.
    Most 11.25 twist 308s will shoot these lights out at 2600fps, give or take very little (+\- 15fps)
    168gr pills like 2750fps.

    Torque and locktite the action screws to 65in/lbs

    Take the bolt apart and clean the firing pin and spring assembly. You’d be surprised if the goop that you may find if this is not a regular priority.

    Upgrade your trigger. Timney, Triggertech, Jewel, Huber, etc

    Stick with these, and quality ammo and things should start to tighten up.
     
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    Adlerkopf

    Private
    Minuteman
    Apr 3, 2019
    3
    2
    Thank you all for the comments.


    I had the same issue, my AI AT with a 308 barrel runs like a raped ape with FGM, Hornady and Nosler factory loads suck hairy goat ass. Why, I have no idea. Maybe Hornady and Nosler really hate the English.

    So I guess it's not that weird to have this kind of results even with quality ammo... I thought any match rounds from a good company would be a good bet, but I will definitely have to try a couple before buying "large" quantities again.

    Oh, Stefan, I'm sorry to hear of your troubles. When you found the few rounds of FGMM, was that recently? From most of your story I was going to recommend checking scope/rings/base and action-to-stock. But if you recently were able to shoot a few rounds of FGMM well then that seems to tell us the rifle is okay.

    If it is possible for you to purchase a reloading press and scale I think that would be very useful for you. You could then either buy factory loaded ammo and make changes in powder charge weight and/or seating depth OR buy reloading components and build ammo that works well in your rifle.

    Yes, I found those after spending 2 or 3 range sessions trying to figure out what was going on. So I think the "weapon system" is ok, but then again maaaybe there is something wrong that just isn't noticeable with that particular ammo.

    It is legal to reload, it's just very expensive to start and there's a lot of paperwork required. I have avoided it because of that and because I was more than satisfied with the FGMM performance. But it seems to be the way to go if I want to continue enjoying this, considering that it's not easy to get hold of FGMM or to find other kinds of ammo that will perform well in my gun.

    You will continue to have this problem with factory ammo.Its not so much the ammo is bad its just is not in the sweet spot (node) that your rifle likes.Re loading is not hard to learn and the pay off at the end of a range day will leave you smiling! Not to mention the huge save up some expensive factory ammo money and go get a rock chucker starter kit.cost savings. Are you allowed to reload in chile? Do you have strict gun regulations?
    Good luck with your dilemma

    Yeah I have read about it but I never thought it could have such a huge impact. The rock chucker starter kit looks really nice and reasonably affordable.
    Local laws are kind of weird. We can have almost anything but we have to do lots of paperwork and pay fees and taxes and stuff.

    Sounds like your rifle likes the 175gr Matchkings.
    Most 11.25 twist 308s will shoot these lights out at 2600fps, give or take very little (+\- 15fps)
    168gr pills like 2750fps.

    Torque and locktite the action screws to 65in/lbs

    Take the bolt apart and clean the firing pin and spring assembly. You’d be surprised if the goop that you may find if this is not a regular priority.

    Upgrade your trigger. Timney, Triggertech, Jewel, Huber, etc

    Stick with these, and quality ammo and things should start to tighten up.

    Will do! Actually I forgot to mention I put a Triggertech Primary in it. Absolutely awesome.
     

    ColdBore007

    Private
    Full Member
    Minuteman
    Jan 2, 2011
    56
    18
    Alaska
    If the action isn’t bedded, this is worth doing on any and all rifles, save for SOME chassis systems.
    Bed the Chamber area (3in in front of action)all the way back to the rear tang…if you want to step it up, you can add some pillars and then you’ll know it’s solid…

    Here’s a good reference:

    Best of good luck!
     
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    Oldmauser

    Sergeant of the Hide
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    Minuteman
    Apr 2, 2018
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    1. check the stock bedding,
    2. check free floating of the barrel,
    3. check the scope mount. mount the scope again in quality mount,
    4. adjust the trigger,
    5. properly install the muzzle brake,
    6. shoot test groups using front rest (Lenzi/SEB or comparable) and a solid rear bag. not a harris bipod,
    7. shoot 5-shot groups with equal intervals between shots.
     
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    Eric_F

    Fake Internet Rank Here
    Full Member
    Minuteman
    Feb 22, 2013
    258
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    Minneapolis
    This sounds like a great use case for a barrel tuner. If they'll ship to you, the ATS works well for me.
     
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