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Posted: 5/17/2014 5:55:52 PM EDT
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I have an M16 A2 clone I built on an Anderson lower with a DPMS LPK, DPMS HBAR non-chrome lined 1 in 9 twist 20 in barrel, CMMG BCG. Nothing fancy, just a basic AR. Went to the range today and at 25 yards found that my rifle was all over the place accuracy-wise. First it was low and to the right, so I adjusted the sights for that, it got better on the next group but on the third, it would be way off from where it should be given sight adjustments and where the last group just was. I'd change to a fresh target and it would do the same thing; all over the place with seemingly little-to-none consistency.
I was shooting Tula .223 55 grain FMJ rounds. I've heard Tula can be iffy at times, but it's cheap and I have a bunch of it. I was attempting to get my rifle sighted in since I have so much of this stuff and will probably end up using it mostly, along with the occasional box or so of the Federal XM193 from Wal Mart or other brass-cased ammo. I checked the rifle just now and the barrel and FSB doesn't appear to be or feel loose. The only play in the rifle is a tiny amount between the upper and lower. I was shooting from a rest off a bench. The rifle was pretty stable the whole time. Is Tula really that crappy? Should I try again with some higher quality brass-cased ammo? I'm also not opposed to it being my fault as the shooter, but I can't think of anything I was doing wrong. Also, wind was almost non existent today. |
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Roaming Zeros will be either the barrel nut not correctly tightened, or the barrel heating up and you inducing barrel torque to it via pressure on the hand guards.
On the barrel nut, when it install, all the bearing area's and threads of both the upper barrel socket and bolt nut surface need to be lubed with a moly grease, the barrel nut torqued to 35ftlbs, back off, retorqued, back off, then on the third torquing, to 35ft lbs, then more (do not exceed 80ftlbs) to index the top spine void to the gas tube channel in the upper receiver. The torquing and retorquing mates the threads to prevent the barrel nut from becoming loose, and if you hit 80ftlbs on the final torque and the top spine void will not index correctly, then loose and try again. As for barrel heat, check your rate of fire, being around 1 shot every 10 seconds or more for the shot string of the mag. For next mags, check the heat of the barrel, and if it too hot to grab in front of the front sight base, then let it cool down before beginning the shot strings of the next mag. Simply, when the barrel gets too hot, it begins to whip more, and cause the flyers. Lastly, two different ammo's will not group the the same place, so you can battle zero in the rifle with Tula, but don't be surprised if the XM-193 ends up shooting inches different at 100 yards using the Tula zero. |
| Thanks for the advice. The barrel should be properly installed as I did use grease everywhere it was required and did the tighten then loosen method. In fact, I had made it to 80 ft-lbs and had to back it off to try again and it should be right at or just a hair above 35 now. |
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