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Posted: 10/16/2015 2:13:48 AM EDT
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I know that barrels are not going to be perfectly center, but how bad does this look? Rebuilt it with the same result. URX 3.1, Larue Stealth 16" barrel, CMMG gas block, Aero Precision upper. Gas block set screws in the pre-dimpled barrel.
I won't get a chance to test fire this upper for a few months, otherwise I would just shoot it and see how it goes. 
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Quoted:
As long as the rails are aligned with the upper, the optic is lined and the rifle operates as designed with no issues, it is absolutely fine. My main concern was optics/sights would require excessive windage to get aligned. I guess I'm just going to have to wait until I can shoot it. |
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Quoted:
My main concern was optics/sights would require excessive windage to get aligned. I guess I'm just going to have to wait until I can shoot it. Quoted:
Quoted:
As long as the rails are aligned with the upper, the optic is lined and the rifle operates as designed with no issues, it is absolutely fine. My main concern was optics/sights would require excessive windage to get aligned. I guess I'm just going to have to wait until I can shoot it. Any chance of boresighting prior? Fairly easy to determine. The best of luck with it. |
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This has come up before with the URX 3.1 rails. KAC URX 3.1 rails seem to have a problem with the slight miss alignment, I have seen this before on here and myself as I have 2 of them and the first one I built had the same alignment problem, not bad like some I have seen but I can see it is off a little.
It seems that either the threads that the barrel nut threads into are off or the threads in the rail are off that thread onto the upper or both. The 2nd one I did I milled the end of the rail that threads onto the upper so there is no gap between the upper and the rail and I did not have any alignment problems at all, it looks perfectly straight inline with the barrel. Now I don't know if that helped but I think it did. Some say you need to lap the upper because that could be causing the problem. Yours does not look that bad. The only thing that will cause is you need to adjust your rear sight more if you are running BUIS. Here are some pics of mine  001 by ORION HALO, on Flickr
 023 by ORION HALO, on Flickr
 020 by ORION HALO, on Flickr
 027 by ORION HALO, on Flickr
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Quoted:
Any chance of boresighting prior? Fairly easy to determine. The best of luck with it. Quoted:
Quoted:
Quoted:
As long as the rails are aligned with the upper, the optic is lined and the rifle operates as designed with no issues, it is absolutely fine. My main concern was optics/sights would require excessive windage to get aligned. I guess I'm just going to have to wait until I can shoot it. Any chance of boresighting prior? Fairly easy to determine. The best of luck with it. Yeah, no iron sights and all my optics are zeroed to other guns. Spent all my money on the URX wrench. 
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Quoted:
This has come up before with the URX 3.1 rails. KAC URX 3.1 rails seem to have a problem with the slight miss alignment, I have seen this before on here and myself as I have 2 of them and the first one I built had the same alignment problem, not bad like some I have seen but I can see it is off a little. It seems that either the threads that the barrel nut threads into are off or the threads in the rail are off that thread onto the upper or both. The 2nd one I did I milled the end of the rail that threads onto the upper so there is no gap between the upper and the rail and I did not have any alignment problems at all, it looks perfectly straight inline with the barrel. Now I don't know if that helped but I think it did. Some say you need to lap the upper because that could be causing the problem. Yours does not look that bad. The only thing that will cause is you need to adjust your rear sight more if you are running BUIS. Here are some pics of mine <a href="https://flic.kr/p/yGgSoP" target="_blank">https://farm1.staticflickr.com/628/21459172619_7ac9a433ec_b.jpg</a>001 by ORION HALO, on Flickr <a href="https://flic.kr/p/yGgS9R" target="_blank">https://farm6.staticflickr.com/5733/21459171809_1dc5b60f0a_b.jpg</a>023 by ORION HALO, on Flickr <a href="https://flic.kr/p/yGb963" target="_blank">https://farm6.staticflickr.com/5693/21458054740_61b03662ed_b.jpg</a>020 by ORION HALO, on Flickr <a href="https://flic.kr/p/yGgS3D" target="_blank">https://farm1.staticflickr.com/724/21459171449_4dc571a13a_b.jpg</a>027 by ORION HALO, on Flickr That looks pretty slick. As long as it looks like it will still zero I'm good with it. One of my 6920s needed windage cranked all the way to the right. to zero. I've considered buying the lapping tool, but I'll probably wait. Or get a Mega billet set. 
Just need to save up more money. Household appliances took priority... 
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Quoted:
Yeah, no iron sights and all my optics are zeroed to other guns. Spent all my money on the URX wrench. Quoted:
Quoted:
Quoted:
Quoted:
As long as the rails are aligned with the upper, the optic is lined and the rifle operates as designed with no issues, it is absolutely fine. My main concern was optics/sights would require excessive windage to get aligned. I guess I'm just going to have to wait until I can shoot it. Any chance of boresighting prior? Fairly easy to determine. The best of luck with it. Yeah, no iron sights and all my optics are zeroed to other guns. Spent all my money on the URX wrench. Im sure you wont have any problems with sighting in an optic. The first one that I built that was a little off was on a seekins billet upper and they are known for having precision machining. I put a Leupold VX•R Patrol 1.25-4x20mm (30mm) in a PEPR QD mount on it and when sighting it in my first shot was about inch low and 1/2 inch to right at 25 yrd. So I don't think you will have problems. Just keep the mount on the upper and don't bridge them. The 2nd one in the pics is a Cero Forge upper from Rainier Arms. I have the lapping tool but didn't use it on either one. |
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