Problems with Accuracy out of 2 AR10Ts

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14 years 5 months ago #4530 by banjobob
Problems with Accuracy out of 2 AR10Ts was created by banjobob
My dad I both bought ourselves new 20" AR10Ts for Christmas. They both have leupold mark 4 6.5-20 scopes on Larue base and rings. Using reloads and every factory load we could get our hands on the best either rifle would do was 2.5-3 inches. We were obviously convinced that since both guns were not shooting like we wanted it had to be the shooters not the guns, but this was confirmed by several other people at our range who are very familiar with Ar10's and 2 stage triggers.

We sent them back to Armalite and was told "the barrels were bad and we're going to replace them" They were out of 20" barrels and eventually they offered to replace them with 24".

The guns shoot much better than before, but not great. With Federal Match 168 the best I have gotten is around 1.5 and usually its more like 1.75 at 100. Reloads are about the same. Redding bushing dies .002 -.003 neck tension, winchester brass 168 and 175 SMK & 42-44gr varget.

Trigger job was performed per the armalite website.

Further insult came when I shot 0.43 5 shot group with my Thompson Encore 15" Pistol in 6BR between groups with the AR10.

Any suggestions would be more than welcomed. I'm getting a little embarrassed when I show up to my range and several members are bragging about their DPMS shooting 1/2" all day long and then ask how mine's doing.

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14 years 5 months ago #4534 by PATRICKLANDRY
Replied by PATRICKLANDRY on topic Re:Problems with Accuracy out of 2 AR10Ts
I have 2 ar10's. Had a custom barrel put on each. They shoot terrible.
I took them both to a different gunsmith.
He told me the flash suppressors were on way to tight.
The crown on both barrels was very bad.
and,The barrels were on way, way, way to tight.
I am out of country right now, I believe they should shoot better ?

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14 years 5 months ago - 14 years 5 months ago #4544 by lotoofla
Replied by lotoofla on topic Re:Problems with Accuracy out of 2 AR10Ts
:(Just to make you feel realy bad, I have a cheapo Remington 700 with a light weight barrel and a plastic stock and the factory trigger set at 3#s that'll shoot under an 1.5" at 200 yard all day long. In case your wondering what my load is, CCI 200 pimers, G.I. cases, 175gr Sierra Match King, using H4895 at 95% of MAX. There was'nt any load developement, I figured that this would make a good starting load and go from there. The same ammo in my AR-10(T) and it's 2 1/2-3".
Tom
Last edit: 14 years 5 months ago by lotoofla.

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14 years 5 months ago #4547 by BUILDING MY SASS
Replied by BUILDING MY SASS on topic Re:Problems with Accuracy out of 2 AR10Ts
Well I am no "match" shooter...but I can shoot less than 1" MOA with my A4 CB...all stock, on my reloads...well that is a whole different animal...I can hit the target...at least...some hit home and others, well I have to say it's me...because I know this gun can shoot...If I am shooting to make a "match hole" I use only Hornady 168gr A-max or BTHP Match...or TAP..then it is "dead on target...not sure what to tell you...but I would ask Uncle ArmaLite in a PM to respond on this thread...see what the factory has to say...
I am sure MSH will add some input as well...(can't wait)
BMS...

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14 years 5 months ago #4548 by Hebs
Replied by Hebs on topic Re:Problems with Accuracy out of 2 AR10Ts
With your reloads, how many different seating depths have you tried? Have you tried different bullets, powders, brass and/or primers? I've changed seating depths by .002 and it tightened up my group by a 1/4- 1/2 inch.

What's your recipe?

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14 years 5 months ago - 14 years 5 months ago #4549 by lotoofla
Replied by lotoofla on topic Re:Problems with Accuracy out of 2 AR10Ts
In regards to seating depth, I have 2 sources. 1) I bought 6, 20rd boxs of surplus M118(not LR) of the same lot number, and made some mesurments of the ammo, and what I found is that all of the 172FMJ bullets were seated at 2.825-30". Despite the long length they do work through my magazines quite well. 2)Off of the internet I found a source that listed all of the military variants of the 7.62x51 NATO cartridge, and found that it listed both the M118, M118(LR), and the M825 ammo that the bullets are seated at 2.830". As to powders it listed IMR 4895, and a 'commercial grade' Winchester (Olin) powder that with further searching found that H-BLC(2) is the exact same 'cannister grade' powder that we as reloaders can buy. As this is a new cartridge for me I made up some starter ammo to see how well or bad the gun worked. Obviously, the Remington loves it. There has'nt been an further reloading study as to powder or bullet depth yet. time will tell.
Last edit: 14 years 5 months ago by lotoofla.

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14 years 5 months ago #4556 by Hebs
Replied by Hebs on topic Re:Problems with Accuracy out of 2 AR10Ts
I would focus on the seating depth in comparison to the lands. Every rifle is different and every bullet is different and will require a different seating depth. How that bullet first contacts the lands when it's fired can really affect the accuracy. As the barrel wears down, the seating depth has to change with it to maintain accuracy. It's easier when you have a seating depth tool. (Sinclair sells them)Your starting point will be the overall length once the bullet just barely touches the rifling. That is your baseline. From there I would work in .002 increments. Load up about 3-4 of each length. Keep in mind that the first shot for each load will be refouling the barrel for that specific load, so your accuracy should improve after that first shot. I wouldn't shoot more than 4 shots before letting the barrel cool.

Right now I'm shooting;

WCR Brass
Sierra 150gr Pro Hunters
45.0gr AA2460 powder
with a SP of 3.222

Attached is my shot group with a 16" stock setup at 100yds.

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14 years 5 months ago #4558 by Hebs
Replied by Hebs on topic Re:Problems with Accuracy out of 2 AR10Ts
Btw, Sinclair has a really good article all about seating depths. Check it out if you like...

blog.sinclairintl.com/2009/03/26/determi...ullet-seating-depth/

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14 years 5 months ago #4559 by lotoofla
Replied by lotoofla on topic Re:Problems with Accuracy out of 2 AR10Ts
Playing with bullet jump becomes a moot point for any of my .308Win rifles as I have measured my throat/leade with RCBSs 'Precision Mic'. I found that with my 2 upper receivers (T), and A-2 plus my Remington M700 that they ALL have a bullet jump of .090-95". This was confirmed by seating a 175gr Sierra Match King out an addtional .150" from the max legth of 2.830* then seating it in slowly till the bullet did not stick in the rifeling. When all of my parts get here, I'll make the match receiver to have a 0.000" bullet jump with the 175gr Sierra MK with an OAL of 2.800. The A-2 will have it for 2.830* so it can shoot most anything without jamming. *2.830 is the specified OAL for the M852, and M118(LR), and yes it will work in your mags.
Tom

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14 years 5 months ago #4561 by Hebs
Replied by Hebs on topic Re:Problems with Accuracy out of 2 AR10Ts
Am I understanding your statement correctly? You're saying seating depth hasn't affected any of your rifles' accuracy?

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