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Posted: 6/26/2007 3:30:09 PM EDT
| Good day. I just received an upper that I had built by a credible source and major company for custom AR15's using a DD Lite 10.0 Rail, Mega Upper, and a barrel and micro gas block. The problem is that I can literally move the rail system 1/4 inch in all directions even after I checked that all of the 6 mounting bolts were tight. I seperated the rail from the mount that goes on the barrel nut (closest to the upper itself) and that mount is all kinds of loose. It seems like the barrel nut is what holds this second mount tight. I apologize for my ignorance, I just really can't believe there is so much play in the rail and need to eliminate it. I appreciate any help you all can offer. |
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On my two builds using the Lite rails, one my AR 6.5 G and one on my LR-308 .500 Phantom, the barrel nut holds the mounting ring very tightly so that when you tighten up the bolts everything is as tight as a tick. I wonder if the builder put the mounting plate on backwards or did not tighten the barrel nut properly. While you may want to fix it yourself, anything you do gives the builder an "out" if something gets mucked up. Better to give him a call. If he has any kind of reputation to uphold he will move your repair to the front of the line and get the upper back to you ASAP. This should not be something that takes him more than a few minutes, but if you muck something up, he may claim no responsibility. |
I have a pretty good idea what happened... The 6 screws FEEL tight to you because they are loctited into place. In all likelyhood, whoever was building the upper stepped away to take a phone call and then did not realize that they left the rail loose. They had already put loctite on the screws with the intention of aligning the rail and locking it all down. Then they came back later and packed up the upper. You really need to send the upper back so they can properly align the top rail while tightening the screws. The whole thing will need to come apart to clean out the old loctite too... And for the record, I did NOT build this upper. 
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I agree with Randall's assessment. The Bolt Up™ Plate behind the barrel nut will move when the nut is torqued to spec. This is for proper alignment. The six bolts clamp the Plate to the forend and sandwich the barrel nut. When installed properly, there will be zero movement or rotation. |
| I would just learn how the handguard is attached to the barrel nut and fix it yourself. It will be pretty easy and will also be a good learning experience. Personally, I don't understand why people have their AR built by gunsmiths, when all quality parts for an AR are designed to be installed by an idiot. |
Some people don't want to buy all the tools to do it right. Some people are not building enough uppers to justify buying the tools.  Some people think they have better mechanical skills than they actually do. Some people just don't have mechanical skills and are smart enough to realize this. Some people feel more comfortable paying a professional to do the job and going that route also makes someone else responsible for the job being done right. Some people are just lazy or can afford to have someone else do it for them. Do you do your own plumbing, yard maintainence and home/auto repairs as well? There's all different sort of people out there.
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Believe it or not, I don't OWN a dremel. I do have an air die grinder and a 4.5" angle grinder, but those are rarely used on gunsmith projects beyond removing permanent muzzle devices and blending feedramps. I use proper machine tools, a Lathe, Milling Machine and Surface Grinder. 
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