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Posted: 12/16/2009 4:36:25 PM EDT
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For quite some time now my AR-15 has been suffering from low precision. It shoots about 3" to 4" patterns at 100yds and is really irritating.
When I bought the gun I thought it was a DPMS but since I didn't know much about them at the time I didn't know what to look for. It turns out that the lower is DPMS and I don't even know what the upper/barrel is so I can't send it to anyone. I've tried several scope an bullet combination's so I don't believe that is it. I know some bullet twist rates work better with different bullet grains and I've only ever used 52gr and 55gr but it used to shoot them just fine. The gun is less than a year old buy the way. |
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Way too little information to even attempt to give advice.
Barrel twist, upper configuration, ammo type being used, will all give us a better idea. Also, how are you benching the rig, such as forearm/rifle pressure points, and regarding the scope use, what mount and scope manufacture as well. Standard group size with a production barrel is around 3 MOA, but with the right ammo, getting it lower than that is not out of the norm. |
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The problem is I don't know how to figure that information out for the upper. There are no markings to indicate manufacture or barrel information.
I'm using a bipod and some shooting bags and I'm 100% it's not my shooting ability. I expect to shoot at leas 1" moa at 100 yds. It was even shooting better than that before which is why I'm frustrated with it's current state, especially since I'm SOL with any manufacturer support. I'm also using a Nikon buckmaster 4.5-14X40 with a Super Sniper S.S.A.L.T mount. Since I last posted I've seen some information about the barrel nut torque and its effects on accuracy. Do you guys think this could be the case? I don't know much about it but if it directly effects your accuracy, if mine wasn't torqued right it could have eventually loosened causing the accuracy to start off good and gradually get worse like it has. |
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A barrel nut cannot just simply loosen if it is the type with the gas tube going through it. It could loosen 1/16 inch or so but no more than that. Give your barrel a good cleaning and use some copper remover such as Barnes CR-10 and get that barrel clean enough to eat off of. Have you been doing a lot of bump firing or shooting the barrel until it is too hot to hold? Is your barrel chrome lined? If not chrome lined and you have been shooting the barrel hot as hell then you could have eroded the throat and it doesn't take that many rounds to do it when bump firing or doing mag dumps. In that case you simply ruined your barrel and will need a new one.
First run some copper remover through it and get every trace of copper out of it and see what happens. That is the easiest and cheapest thing to test before getting too concerned. |
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Front end system ?
You mention a bipod, so is the barrel free floating or not, with the bipod attached to the hand guard system and not putting any stress on the barrel? Although Bigbore is right about a barrel nut, that had it been correctly tightened to begind with, it should not be loosening up now. But, if the barrel nut was borderline tightened to begin with, then it could be a loose barrel nut the problem at hand. As for cleaning, depending on the round count down the barrel (didn't tell us this either), if it has a FS with higher round count, then it may be time to pull the FS to get the barrel crown clean as well. |
| Between 500 and 1000 rounds through it. I've never shot it so much as to heat up the barrel, not even close. I've cleaned the barrel several times but I haven't use any specialty cleaners just regular solvent an then oil. The fore grip is standard, not free floating. |
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Sweets copper solvent to clean the bore of the barrel.
BreakfreeCLP to clean and lube everything else on the rifle. Sweets is a very aggressive copper dissolving agent, and will not require much scrubbing to remove all the copper fouling in the bore. Do this step first. The chamber should be cleaned with a chamber brush and can be done while you are cleaning the bore, but once cleaned, Flush the mess out of the muzzle with BreakfreeCLP, then it chased with dry patches. Sweets leaves nothing behind, and although BreakfreeCLP has Teflon in it,and will take around 14 shots to remove the traces amounts out of the rifling to allow the barrel into group settling (even when you have path wiped all of it out of the bore), the residual CLP after cleaning will leave behind a protective layer in the bore to prevent rusting between shooting events (short period storage). Note: Between the sweets/sweets/brushes/ dry patches being forced out of the muzzle, it will help to keep the muzzle crown semi clean, But there will come a time that you will need to pull the FS to give the crown a proper cleaning. Also, make sure that the bore is bone dry before shooting the weapon (hence more CLP in the bore for a semi longer period between shootings). As for the upper bearing areas, a good coat of CLP just before firing will make sure that the action runs without problems. As for ammo, not sure what you are running, but do try a couple of boxes of M-193 for a base test. This ammo should turn in at least a 1.5MOA group in most barrels, and would be a good base line for testing. If the ammo prints as stated, then with hand loaded ammo more in favor of the barrel harmonics and twist, you should be able to stay in the MOA for a 10 shot group with a clean bore and no tension forced on the barrel. |
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