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Posted: 9/27/2011 9:02:23 PM EDT
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Hi all,
Hoping you can help me out. I'm fairly new to ARs, and have a standard Bushmaster M4 carbine. No mods other than a magpul hand guard and fore grip. I've probably put 1,000 rounds through it over the past 6 months or so. The last two trips to the range I've noticed pretty significantly reduced accuracy once I've gone through a magazine or two of fairly slow fire from a bench. At the indoor range I shoot at occasionally, the farthest out you can go is 25 yards. The first magazine or two using either my 1.5-4 power Leupold or my Primary Arms red dot, I can get a 20 round group about 2 or 3 inches in diameter without really trying. After that, the groups open up to 6-8 inches, and the rounds are all over the place. One to the left, one to the right, one up, one down, etc. I'm quite confused. Any ideas? My first thought was that maybe the barrel nut somehow worked loose, but I'm not sure if that's even possible with the gas tube in there. The optics are on there firmly, and I even replicated the issue using the removable carry handle. Thanks for any help you can give! Nathan |
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Quoted:
Hi all, Hoping you can help me out. I'm fairly new to ARs, and have a standard Bushmaster M4 carbine. No mods other than a magpul hand guard and fore grip. I've probably put 1,000 rounds through it over the past 6 months or so. The last two trips to the range I've noticed pretty significantly reduced accuracy once I've gone through a magazine or two of fairly slow fire from a bench. At the indoor range I shoot at occasionally, the farthest out you can go is 25 yards. The first magazine or two using either my 1.5-4 power Leupold or my Primary Arms red dot, I can get a 20 round group about 2 or 3 inches in diameter without really trying. After that, the groups open up to 6-8 inches, and the rounds are all over the place. One to the left, one to the right, one up, one down, etc. I'm quite confused. Any ideas? My first thought was that maybe the barrel nut somehow worked loose, but I'm not sure if that's even possible with the gas tube in there. The optics are on there firmly, and I even replicated the issue using the removable carry handle. Thanks for any help you can give! Nathan This can be typical behavior for a non-floated handguard. As the bullet crashes down into the lands and grooves, the barrel moves in a tiny circle. When the barrel heats up it interacts with the handguard in a different way or place. Extreme accuracy is about repeatability and that is why competition rifles are floated so the barrel never touches the handguard. |
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Quoted:
So many variables... so little time... Can you give more info.... like, are you using some sort of rest? Gun vise, anything like that? - Clint Thanks for the replies guys. I'm not using a visa or gun rest. It's not ideal for sure, but I'm resting the gun by putting the vertical fore grip on the range lane bench and sitting in a chair. I know that can influence poi when you don't have a free floated barrel, but I was most concerned/surprised by the drop in consistency when warm. Especially at only 25 yards. |
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