Questions on AR10T accuracy

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11 years 2 months ago #28800 by waynzwld
Questions on AR10T accuracy was created by waynzwld
I recently got an AR10T 20" and have tried 7 different powders with Sierra 168gr SMKs and OAL's of 2.800 to 2.830 (some of the 2.830 loads dragged on the mag and did not feed).
The best group shot so far is 1.186" @ 100yds with 42grs of RL15 with the Hornady OAL set at 2.820. After checking the seating depth with a Hornady OAL (formally Stony Point) gauge, I found out that there is about 0.110" from the 2.800 inch OAL to the lands in this barrel. That is quite a jump for the bullet. Is this normal for AR10s?

I could seat the bullets out longer and shoot by single loading, but this defeats the reason I purchased the AR10T.

Is this the best this rifle is going to do? Would I get better results with 178gr bullets?

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11 years 2 months ago #28803 by Siscowet
Replied by Siscowet on topic Questions on AR10T accuracy
Machine rest or just using a stock support?

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11 years 2 months ago #28807 by OleCowboy
Replied by OleCowboy on topic Questions on AR10T accuracy
I am with Sisco on this. You have shot 7 different configs and you are not getting sub moa. I would look first at shooting technique with THIS weapon. Its prob different from other weapons you shoot in size, weight, and design.

Then I would look at your consistency factor. Is it repeatable? Fire 3 rds, measure your spread and hit pattern, mark them and fire 3 more, repeat till you have enough for an analysis. I would do at least 12 iterations. Throw out the tightest group and loosest group. Look at the other 10 and see what the +/- is. IF its consistent then look to tune your weapon, you have great shooting skills. If its a big spread then look at your 'rest' and technique, something is shifting.

Let us know...
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11 years 2 months ago - 11 years 2 months ago #28823 by waynzwld
Replied by waynzwld on topic Questions on AR10T accuracy
This is off a concrete bench with a front rest and bag and a bag under the butt.

I shoot as good as the rifle will shoot. With my AR15 I am good for consistent 1/2 MOA,
my 221 fireball good for 1/4 MOA. So I do not think it is me.

As for the 308 reloads, I have used IMI brass & Hornady match brass, tried 168gr Hornady HPBT's
along with 168 SMK's. Using Lee dies with factory crimp die

Heck, my M1A with open sights and Hertinberger ammo would do 3/4 MOA off this setup.

here is my best group with the AR10:

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Last edit: 11 years 2 months ago by waynzwld.

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11 years 2 months ago - 11 years 2 months ago #28824 by jtallen83
Replied by jtallen83 on topic Questions on AR10T accuracy
What will it do with a 20 round group? For me that is the real test of an AR platform rifle. You can shoot 3 and 5 round groups from about any bolt gun. Open her up, she was made to shoot fast and often, that's where it will shine.
I'm starting to wonder what the T is all about, my basic flat top shoots as well as most T's I hear of and I'm not a good shot!
I've gotten my best groups from some FN NATO ball ammo, the FGMM doesn't get close at 100 yards compared to the ball ammo. My best handloads to date have not beat ball ammo at 100 yards, I'm told the larger bullets will start to shine at longer ranges but I lack the time to work on it now. I use 2.80 for OAL in handloads. Hornady FL dies and a Lee crimp die if I use it, so far slimming the expander a touch has worked fine to avoid any crimp. :usa:
Last edit: 11 years 2 months ago by jtallen83.

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11 years 2 months ago #28825 by waynzwld
Replied by waynzwld on topic Questions on AR10T accuracy
I have some more reloads with different seating depths on 10 each. This was my next test.

I know rifles can be finicky, I have a Rem 700 22-250 sporter barrel that drove me crazy,
couldn't get it to shoot better than 2" @ 100. Traded it off 2times, and ended up with it again. Tried a bunch more loads and finally found the only load it will shoot well.
Speer 52gr fb with 35.5grs of H4895 @ 3675. It will shoot this load off a bench into 3/4" @ 100 even when shot fast for 5 rounds. It's my walking varminter.

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11 years 2 months ago - 11 years 2 months ago #28826 by 10-76
Replied by 10-76 on topic Questions on AR10T accuracy
Take a look at this series on YouTube, and compare your techniques...what barrel length?

Last edit: 11 years 2 months ago by 10-76.
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11 years 2 months ago #28828 by Siscowet
Replied by Siscowet on topic Questions on AR10T accuracy

waynzwld wrote: This is off a concrete bench with a front rest and bag and a bag under the butt.

I shoot as good as the rifle will shoot. With my AR15 I am good for consistent 1/2 MOA,
my 221 fireball good for 1/4 MOA. So I do not think it is me.

As for the 308 reloads, I have used IMI brass & Hornady match brass, tried 168gr Hornady HPBT's
along with 168 SMK's. Using Lee dies with factory crimp die

Heck, my M1A with open sights and Hertinberger ammo would do 3/4 MOA off this setup.

here is my best group with the AR10:

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Do you start with a cold barrel? Or do you do some warm up shots? Also I assume you did the recommended break in procedure. I frankly am at a loss what might be the issue. What primers are you using and are you using any crimp at all?

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11 years 2 months ago #28831 by 13fcolt
Replied by 13fcolt on topic Questions on AR10T accuracy
Looks like you are on the right track. I'd check the throat depth and get the most accurate measurement that you can. From there, I would compare against different bullet manufacturers and see if a different ogive is going to work better.
Your consistency has me thinking that the bore, load, and technique are not the issue here, but .110 off the lands is huge and is why I think it's worth re-checking just to be certain. It is possible that your chamber is just too long, these things happen and armalite will take care of it. I know the thought of sending it off really sucks, but it may be the best option vs. the cost of re-barreling yourself.


I'd have to dig out my books to give exact numbers, but from memory I run 175smk 2.810-2.820, whichever is getting me .030ish off the lands and shoot wonderfully if I do my part. Even 2.800 factory loaded 175smk will work, just pushing me out another 1/4-1/2 moa @100.
On the filp side, I have a handful of Berger 168 vld that are so long they couldn't hit the ground if I dropped them because they are secant ogive and very picky about being exactly .012 off the lands and will not go in a mag at that length.
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11 years 2 months ago #28840 by OleCowboy
Replied by OleCowboy on topic Questions on AR10T accuracy
OK I will make some assumptions: You are a sub moa shooter (you did not say that up front, been nice if you did). I am also wondering if the group pictured shows the first rd was at the far left and each rd afterwards moved to the right. OR???

That said Sisco asked if the bbl was cold, how long between rds. Do you have a pic of your worst group?

Looking at the pic, which is but a shred of evidence I would certainly lean towards a gun issue, from cold to warmer bbl if you are doing nothing else to make adjustments.

How often or are you adjusting your sights to focus in on the group more. I could not get a tight enough group once. I was dead on the X fist rd, sec rd it drifted to the left but on line with the X, 3 rd drifted an EQUAL amount the the left for the same plane. I kept adjusting the sights and kept repeating the same group over and over and over. I spent better part of the morning. FINALLY it dawned on me that it was my rear iron sight. I could adjust back to the X every time after my 3 group, but the drift repeated itself.

The iron sight was used when I got it and I guess the click stops had just worn enough that the 30-06 was enough kick to click it on its own.

NOT saying this is the issue, rather providing a example of the gun causing the issue, cause like you I am (was) a good shot, REAL good and I do it off either shoulder. Today I just hit the target which is still good enough for the kill, age has a funny way of degrading your eyeballs...

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