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Posted: 10/29/2014 1:32:59 PM EDT
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Hey all, I've got a question. I'm fairly new to the AR scene, I bought my first one about 2 months ago. It's a used Colt light carbine model with a few minor upgrades. I intend to use this mostly as a hunting gun, so I removed the red dot and iron sights that were included with the gun and attached a used scope. The scope is mounted with Nikon p-223 cantilever rings with loctite on the threads, and tightened as much as I dare. I went to zero the rifle yesterday, and it's definitely not what I expected.
I've been mounting scopes and zeroing rifles my whole life, and I've never run into an issue before. But then again, all of those rifles were purpose built hunting rifles and the scopes were all new. My last rifle shot sub-MOA groups with ease. However, the best I could do with my AR yesterday was a 4" group at 33 yards. I know the rings are mounted to the gun well, and that the scope is mounted in the rings well, so my concerns are that either the scope is broken or the gun is broken. 
For reference, the red target dot is 1.5" in diameter. Or maybe I'm just inexperienced with ARs and this is acceptable accuracy. Any help is appreciated. |
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Quoted:
Hey all, I've got a question. I'm fairly new to the AR scene, I bought my first one about 2 months ago. It's a used Colt light carbine model with a few minor upgrades. I intend to use this mostly as a hunting gun, so I removed the red dot and iron sights that were included with the gun and attached a used scope. The scope is mounted with Nikon p-223 cantilever rings with loctite on the threads, and tightened as much as I dare. I went to zero the rifle yesterday, and it's definitely not what I expected. I've been mounting scopes and zeroing rifles my whole life, and I've never run into an issue before. But then again, all of those rifles were purpose built hunting rifles and the scopes were all new. My last rifle shot sub-MOA groups with ease. However, the best I could do with my AR yesterday was a 4" group at 33 yards. I know the rings are mounted to the gun well, and that the scope is mounted in the rings well, so my concerns are that either the scope is broken or the gun is broken. <a href="http://s821.photobucket.com/user/twdant/media/IMG_2332_zps3d5d8067.jpg.html" target="_blank">http://i821.photobucket.com/albums/zz135/twdant/IMG_2332_zps3d5d8067.jpg</a> For reference, the red target dot is 1.5" in diameter. Or maybe I'm just inexperienced with ARs and this is acceptable accuracy. Any help is appreciated. not to sound like a jackwagon, but give the rifle a thorough, detailed cleaning and lubing....especially the barrel. these rifles will deliver excellent accuracy. |
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Barrel cleaned with a good copper solvent like Sweets to remove any copper fouling in the bore?
Rate on fire not greater than a few shots every min so you don't over heat the barrel to cause the barrel to over heat spray? Since the barrel does not have a float type hand guard, rifle sand bagged as close to the upper receiver on the hand guards so you are not flex torquing the barrel from shot to shot. And lastly, what ammo are you using, since some value brands ammo's are just not going to be consistent/will not group well. |
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Thanks for the replies.
The rifle was thoroughly cleaned and lubed when I bought it. Before this picture was taken, I had 90 rounds through the gun since it had been cleaned. I mounted the scope the first time and shot with Winchester 62 gr. HPs for hunting, and they wouldn't group any better than that picture. So I removed the scope and remounted it, then shot with Federal 62 gr. green tips (because I couldn't afford any more HPs), and that's when I took the picture. I'm confident it's not a dirty rifle problem. My last (sub-MOA) gun was a Tikka, and it was really picky about being clean, so I learned about dirty rifle fussiness. My next step is to remove the scope and replace the irons and red dot and try again at the same distance. However, I'd still like to put a scope on this gun. Is there any reason I couldn't find a suitable scope setup for an AR? |
| The barrel may not be properly torqued. If one of the upgrades involved replacing the barrel nut, such as the addition of a rail, then the barrel nut may not have been installed correctly. If the crown is not damaged, then take down the upper receiver and check that the barrel nut is greased and torqued to 30-80 pounds. Also, do you have any idea of the round count through the rifle? |
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The most important factor in accuracy is quality ammo. A 4" group at 33 yards is pretty bad. US GI ball ammo must be able to shoot a 4" group at 100 yards to be accepted into inventory. Also pretty bad. Your ammo/rifle/shooting experience translates into a 12" group at 100 yards. Horrible by any standard.
What type of ammo are you using? Ball ammo is junk 90% of the time, but usually can shoot decent groups at that short of range. Russian ammo is better left to the Russians. It's junk all of the time. If you want to discover your rifles accuracy potential buy some 52/52 grain match ammo. It normally shoots the smallest groups from any rifle regardless of twist rate. My rifles will put all those bullets through the same hole at 33 yards. They are superb inside 100 yards. Sierra Match Kings work best for me, but Nosler and Hornady bullets shoot well too. Some rifles prefer those brands, but most like the Sierra's best. Are using sand bags front and rear? Trigger follow through? Does the bolt face and locking lugs look worn with finish missing? Does the rifle look like it's been road hard and put up wet? Does it look relatively new? An AR barrel will last around 3000 rounds if run hard on full-auto. Most semi-auto rifles will last at least 10,000 rounds unless the owner shoots Russian ammo and does magazine dumps as a matter of course. Casual shooting with decent maintenance will allow an AR barrel to last a very long time. High heat kills barrels. I would look at ammo first before going further. As already suggested a thorough cleaning never hurts a thing. |
My ammo is Federal 62 grain green tips. I shot again tonight with a different mount and (admittedly low quality-Barska) scope, and this is what I got at 33 yards:
That's a 10 round group with no sight adjustments. I took the FH off to look at the crown, but I don't really know what comprises a good crown. There is some crud on the face of the muzzle that wouldn't wipe off with a cloth. Here's the picture: 
The bolt face and other major components look like they're in good condition, but not brand new by any means. By looks and considering the previous owner, it's probably two or three thousand rounds old. I plan on removing the scope and trying straight iron sights again tomorrow. I'll report when I have results. Thanks again for all the help. |
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Great deal of fouling on the crown, as well as the rifling.
Use something like Sweets copper solvent to clean the rifling and the crown, and both should be Chrome when cleaned correctly. Also, with what looks like the barrel removed from the upper receiver, now would be a good time to make sure that the barrel is installed correctly, with the Moly lube used on all the barrel extension/barrel nut and thread bearing surfaces, with the barrel nut torqued 35ft plus, but not to exceed 80ftlb to index the top barrel nut spine void to the upper receiver gas tube channel. On the FS, new crush washer used, and do not over torque and end up bending the last inch of threaded barrel. |
| Barska scopes are junk. My friends "Competition" model puked on it's first trip to the range. His kids bought it for him as a gift. Turning the elevation and windage adjustments has little relationship to bullet impacts on target. Anything this poorly made is automatically suspect. |
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GOOD GRIEF. Why does a problem this simple have to be so hard to fix?
The barrel actually wasn't removed from the upper for that picture, but I figured it would be a good idea to take it off and clean it. Plus, I like to understand how my guns work, and taking them apart is about the best way I know of to get familiar with the insides. So I bought an armorer's tool and started the teardown. I got the FH, quad rail, and gas block off, so it was time to loosen the barrel nut. I noticed that the nut looked pretty damaged. There are several spots where the finish is completely worn off exposing the raw metal underneath, and that two of the barrel nut's teeth were missing. They looked like they had been rounded off. So I clamped the gun in my vise and proceeded to break off two more teeth trying to get the damn thing loose. If the maximum torque spec on the nut is 80 pounds, I can confidently say that this one is WAY overtightened. It wouldn't surprise me to learn it's more like 120 pounds. I couldn't budge the nut with all my strength, and eventually two more teeth broke off. Where the hell do I go from here?? |
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Nevermind, I spoke too soon. A liberal dose of penetrating oil and a few hammer blows loosened it up. Here's what it looks like now, although it wasn't much better before I worked on it:
http://i821.photobucket.com/albums/zz135/twdant/IMG_2359_zpsc1822345.jpg http://i821.photobucket.com/albums/zz135/twdant/IMG_2358_zpsd912f982.jpg So now I'll clean the hound out of it and try again with just iron sights. That barrel nut will be replaced. |
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Quoted: Wow! That is seriously buggered up. Time for new barrel nut, attached with the proper torque. You may want to check the face of the upper as well to be sure it's square with the bore. Over-torquing may have skewed it |
Well I got it back together properly (with the buggered barrel nut, the new one will be here tomorrow), got the irons back on and got her to the range for a test drive, and my worst fears are relieved. The problem is not the rifle. Here's a picture of my first 6 rounds:
The round out to the right was the first, before I zeroed the sights. The last five are inside of an inch, holes touching. For comparison's sake, here's a picture of the previous shots, fired just before the group above with the busted scope:
Same distance (33 yards), same ammo (62 gr. Federal green tips), same shooter, same rest, same magazine, even. I'd still like to see how it groups at 100 yards, but I don't trust my iron sight ability to give me a true result at that distance. Once I get some decent glass on the gun, I'll try again and repost. As far as the previous botched job on the barrel nut: I didn't look closely at the receiver to see if it was warped, but I'm not sure I could tell by eyeballing it anyway. In my mind, the biggest problem one might see from a warped receiver is cycling issues moreso than accuracy issues, and I've got about 150 rounds through the gun post-barrel nut crap job, and no cycling issues thus far. I did look at the threads though, and they look fine. I also didn't see any signs of loctite, so I guess whoever put the nut on last just overtorqued the piss out of it. Anyway, thanks for all the help and suggestions. Part of the fun of having such a modular weapon system is that I get to learn about it by taking it apart. It's nice to have this community on hand to help me if I get into a tight spot. |
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