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Posted: 6/30/2015 10:58:24 PM EDT
| I recently completed a build and took it out to shoot. At 25 yards, with the rear sight centered it would not hit paper. 15 clicks to the right. Still not on paper.......cranked it to the right until it stopped. Then on paper, just. Way to the left still. The groups were good but just way left. I assume the front sight base is canted to the right. Is there a way to correct this or do i need a new barrel? Its a f marked sight base that is taper pinned. The rear sight is a knights armament flip up. |
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Why assume??
That much of a deviation should be noticeable. Is the centerline of the upper the same as the centerline of the bore? Is the sight canted on the barrel or is the barrel not clocked correctly in the upper? Did you mount the front sight or did it come that way? Is the rear sight level on the rail? |
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If your front sight base is far enough off to cause that effect at 25 yards, I would think you'd be having cyclic problems due to gas port/block alignment. That is assuming the fsb is canted, and not the barrel itself. There might some give where the barrel is indexed to the receiver, affecting the timing/ position of the port and fsb. |
| The sight looks level on the rail. The barrel appears centered. The sight was installed on the barrel when I got it. The rifle cycles with all types of ammo, wolf steel included.I will spin off the barrel nut to make sure it isn't canted and there is nothing wrong with the pin. |
| Nothing is jumping out at my except the front sight looks like it's off to the right and the front sight itself looks like it was cast poorly. I'll do a little more digging. I'm gonna try it with a different rear sight and then I'll take the barrel off. I'll update the thread when that's done. Thank you for the help. |
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Nothing is jumping out at my except the front sight looks like it's off to the right and the front sight itself looks like it was cast poorly. I'll do a little more digging. I'm gonna try it with a different rear sight and then I'll take the barrel off. I'll update the thread when that's done. Thank you for the help. Front sight bases are normally forged, not cast. There have been some cast units in the past, but few and far between. |
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I had a similar problem, not quite that far off. After taking everything apart and checking all suspect parts, putting it all back together again, at least 3 times. A friend had me bring him the upper receiver. He ran his lapping tool on it, front face was well out of square, 10 minutes later done. Put it all back together, centered rear site, right on target! Midway has some on clearance; |
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I had a similar problem, not quite that far off. After taking everything apart and checking all suspect parts, putting it all back together again, at least 3 times. A friend had me bring him the upper receiver. He ran his lapping tool on it, front face was well out of square, 10 minutes later done. Put it all back together, centered rear site, right on target! Midway has some on clearance; http://www.midwayusa.com/product/821295/wheeler-engineering-delta-series-upper-receiver-lapping-tool-ar-15?cm_vc=ProductFinding Strange. The uppers I've barrelled (5) have had such a tight fit between the upper and the barrel extension that it seems like it would be impossible for a barrel to have it's alignment altered by the face of the upper. When I slide a barrel into the upper, there's zero play...it's a really tight fit...like hard to rotate the barrel tight. I would think you'd just have less contact between the face and the flange of the barrel extension if the face wasn't square. With yours was there play between the barrel extension and the receiver when you just slid it in (before tightening the barrel nut). |
| Ok, I had the front sight base ground down and used it as a low profile gas block. Installed an SLR 14" rail with a magpul front sight and a knights armament 600 micro rear sight. It is now shooting the way it should. 5 clicks right on the rear and 4 clicks up on the front. The front sight base was cast/forged wrong, and was canted to the right. Since I had the barrel cut down and re-crowned the manufacturer would not honor the warranty. I spent a little more than I wanted but the SLR rail is great and closer to what I originally wanted. Ill post a pic when I can. Thanks for all the advice. |
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Ok, I had the front sight base ground down and used it as a low profile gas block. Installed an SLR 14" rail with a magpul front sight and a knights armament 600 micro rear sight. It is now shooting the way it should. 5 clicks right on the rear and 4 clicks up on the front. The front sight base was cast/forged wrong, and was canted to the right. Since I had the barrel cut down and re-crowned the manufacturer would not honor the warranty. I spent a little more than I wanted but the SLR rail is great and closer to what I originally wanted. Ill post a pic when I can. Thanks for all the advice. What vise tool were you using to install the barrel? |
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A receiver extension tool was welded to a piece of square stock that was held in a vice. So it was a Reaction Rod style tool, that is what I expected... You don't really see this issue that often because the current trend is to just use a gas block and not a standard FSB like you had. If most people were still installing barrels with standard front sight bases in this age of the Reaction Rod this is the most common issue that would be seen, more so than index pins shearing in half. Just like it was back when barrel blocks were common for barrel installation. Don't get me wrong, it is possible that your FSB was installed canted at the factory but it is very unlikely because of the jigs that are required to do the job of aligning and pinning the FSB. What has most likely happened is that during the barrel installation torque procedure the upper was twisted to the left and the index pin pressed into the right side of the index pin notch of the upper receiver. If you took everything apart you would probably find an index pin shaped indent on the right side of the index pin notch. Well, at least the index pin didn't shear this time. 
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| I did take it apart. There was no problems with the pin or the notch. I did not take any photos but I think the fsb was canted along with the fact that the front sight base looked poorly forged/cast. I ground it down and used it as a low profile gas block because it was what I had. I was trying to keep the build a low budget one till this happened, ha ha. |
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I did take it apart. There was no problems with the pin or the notch. I did not take any photos but I think the fsb was canted along with the fact that the front sight base looked poorly forged/cast. I ground it down and used it as a low profile gas block because it was what I had. I was trying to keep the build a low budget one till this happened, ha ha. Well anything is possible I guess. Who made the barrel? |
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I did take it apart. There was no problems with the pin or the notch. I did not take any photos but I think the fsb was canted along with the fact that the front sight base looked poorly forged/cast. I ground it down and used it as a low profile gas block because it was what I had. I was trying to keep the build a low budget one till this happened, ha ha. did you ever mark the barrel gas port and compare that to the gas tube alignment? if you were putting a wrench on the barrel nut and holding the front sight with your free (left) hand.. you could have easily pushed the FSB off alignment.. |
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