Armalite AR10TBNF Not Grouping

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13 years 10 months ago #6399 by Howard Roquet
Armalite AR10TBNF Not Grouping was created by Howard Roquet
I bought a new AR10TBNF, 20" NM barrel and trigger in December, 2010. At mt first range session, my groups were 3-4". I zeroed with factory ammo and then moved on to reloads. I have been reloading for decades, literally, and I've been quite puzzled by the results with the AR10. I followed all the break-in procedures. On my second range session, I couldn't believe that I had everything with me but inadvertently left the magazines at home. However, I loaded the rounds manually one at a time and, low and behold, my 5 shot groups were either one shot holes (1/2") or 4 all touching with one off about 1/2". This held true for 60 rounds.

I did two things for my next visit to the range; tightened neck tension without crimping and crimping some moderate, some heavy. Altogether, another 60 rounds. Results feeding with magazines were the same as the initial visit, 3-5" groups (both factory and reloads). At the same session, I again inserted five rounds by hand and achieved super tight groups, 1/2 to 3/4" (all at 100 yards). When using the magazines, I measured the OAL in the bottom 3 rounds before and after firing the first 2 rounds; no perceptible movement. However, after simply cycling rounds through the rifle, I noticed some serious scratches on the bullets that would effect the flight of the bullet. I called Armalite and answered all their questions and they said send it back. I did send it on Friday (1-14-11).

Has anyone had this issue? I'll keep you posted on Armalite's response.

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13 years 10 months ago #6400 by foxhunter
Replied by foxhunter on topic Re:Armalite AR10TBNF Not Grouping
That sounds really weird to me. No clue. However, it sounds like you have a really accurate single shot rifle there.

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13 years 10 months ago #6401 by JustMe
Replied by JustMe on topic Re:Armalite AR10TBNF Not Grouping
Howard,

I have the same AR-10T and I have the same scratches. Read my thread on "Round jammed in chamber."

I believe the scratches are caused by the two feeding ramps. I think the ramps are manufactured too sharp or have spurs on them. It has been putting scratches on my bullets and deep gouges on the shoulders of my brass. I may have to send mine back to get the ramps rounded a little and the chamber inspected for spurs.

I have been getting consistent 1/2 to 3/4 inch, 100 yard groups using hand loads of 46.0 gr of Varget pushing a 155 Palma SMK bullet. I have the 1:11.25 twist 20" barrel. I haven't tried to single load mine. I have only used the clip.

What load are you using?

Jer

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13 years 10 months ago #6403 by Howard Roquet
Replied by Howard Roquet on topic Re:Armalite AR10TBNF Not Grouping
Jer

I am loading Sierra MK 168's and a variety of powders; H4895 (41.7 grs), Varget (44.0), H335 (40.0) and I even made up some with IMR3031 (42.0). I have gone from 2.810 to 2.840 on OAL as they still run through the magazines and put the bullet closer to the lands (I determined the OAL with a Hornady LNL OAL gage). For the record, I also loaded some early on at 2.756. All had the same basic results using the magazines, 1 1/2" with a couple of fliers. The order of fire in which these measurements were taken varied; sometimes the first or second round would be fliers.

I believe your thoughts on the ramps being too sharp or having spurs on them might be the case. I have not had any serious dings in the brass, but I have had the serious scratches on the bullets, maybe more so than yours in that you're getting reasonable rsults with your groups. I am anxious to hear from Armalite and will keep everyone posted on their feedback.

I load for my M1 Garand, my son-in-law's Mod 700 308 (same loads as I'm using), my Rem 700 22-250, a Bushmaster 223, etc., and experience none of the issues I have with the AR10. I find this to be a whole new level for achieving "nail driving" results.

Thanks for your reply, Jer. I appeciate your insight.

Howard

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13 years 10 months ago #6405 by JustMe
Replied by JustMe on topic Re:Armalite AR10TBNF Not Grouping
Howard,

I also tried a few different powders. See my thread entitled, "My First AR-10T BNF Range Session" 6 Months ago.

I've pretty much settled on the 46.0 gr of Varget, but may go to 48.0 grains as it was also very consistent and tight grouping. May also try feeding them one at a time instead of using the clip and see what happens. I've found that the primer I sellect also made a big difference on accuracy. I've had my best luck using Fed 210 match primers. I'm loading mine to 2.80 and 2.855 OAL. Both lengths shoot well, so I've settled on 2.855 which just barely fits in the clip.

Jer

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13 years 9 months ago #6487 by Howard Roquet
Replied by Howard Roquet on topic Re:Armalite AR10TBNF Not Grouping
Friday, February 4, will be three weeks since my local dealer sent the AR10 back to Armalite. I have not heard anything from them so far. I emailed them today inquiring about status. If I don't hear from them by the end of Friday, I will call them on Monday. Just wanted to post a short update. Hope I'm not in for some long ordeal.

Howard

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13 years 9 months ago #6492 by Howard Roquet
Replied by Howard Roquet on topic Re:Armalite AR10TBNF Not Grouping
Just an update; I received a prompt email response from Armalite advising as follows: "Your rifle has been worked on by the gunsmith and is ready for test fire acceptance". No other info available at this time.

Howard Roquet

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13 years 7 months ago #7086 by Howard Roquet
Replied by Howard Roquet on topic Re:Armalite AR10TBNF Not Grouping
Armalite shipped my AR10 back about 4 weeks ago. At that time, I took it to the range and fired both Black Hills Match 168 BTHP as well as my reloads using H4895 and Sierra MK BTHP's. Conclusion, better, but still not a tack driver by any means. I was then out of town for three weeks and just returned this past week.

Yesterday, I went to the range again. I fired the Black Hills ammo and achieved an average group size of 1.58". I threw out the highest group (1.75") and this left a bottom line of 1.40"; totally unacceptable. I had the same basic results with the reloads, except that they achieved .88" at 100 yards when loaded as singles without the magazine. Also, shooting my Rem 700 Tactical (only a 16" barrel) with the same ammo, I achieved a group size of .375" at 100 yards.

The rifle is going back to my dealer tomorrow. I have fired almost 700 rounds through this rifle without any significant improvement. Armalite polished the ramps, etc. and some improvement was achieved, but not acceptable based on the latest results. As to the "repairs" they made, no detail was provided. I'll report on my dealer's/Armalite's feedback. When I bought this rifle, I received a letter from Armalite stating; "Congratulations on buying an Armalite! You won't be disappointed". I beg to differ.

Howard

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13 years 7 months ago #7088 by JustMe
Replied by JustMe on topic Re:Armalite AR10TBNF Not Grouping
Howard,

Sorry to hear about your problems. Mine is still shooting 1/2-3/4 inch groups from magazine feeds. Did their smoothing of the ramps eliminate the brass and bullet gouging/scratching?

Jer

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13 years 7 months ago #7092 by Howard Roquet
Replied by Howard Roquet on topic Re:Armalite AR10TBNF Not Grouping
Jer

I do have some more info re the work at Armalite, although not detailed nor explained in any way. Comment: REMOVE BURR FROM RAMP, POLISH RAMPS, CLEAN COPPER. Comment: REPLACE BOLT AND CAM PIN. Comment: TEST FIRE - O.K. They mention also an AR10B BOLT Phosphate Finish and an AR10B CAM PIN.

Scratches on bullets still present, but reduced. Bullet dents minimized. With that said, I have no idea how they test fire rifles. If they fired 5 rounds and achieved a 1/2" group, they did not provide any such data. This whole exercise has been very frustrating, especially after firing in a very methodical and measured manner approximately $400 in ammunition, both factory match grade and good reloads with all the same result.

I'll let you know what my dealer/Armalite says. But I'm certainly not going to purchase any additional ammo to waste testing this rifle. Like I've said, I stuck with this longer than most and gave it every chance to function properly.

Thank you for your interest, Jer.

Howard

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