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Posted: 12/1/2008 5:07:20 AM EDT
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i bought a yhm upper reciever and a yhm diamond series rail.its the kind of rail that screws on to the reciever and im not sure about the fit.
i would have thought this thing should screw on very tightly but this is what happens when i try to screw it on all the way. 
this is what it looks like with one less turn. but im not sure if that little gap is ok. and i have yet to put the screws in the side. 
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It does not look like you have the barrel nut timed correctly. when the barrel nut is timed correctly you should be able to slide a gas tube into the upper receiver and it be inline with the barrel. then when you screw the quadrail on you will be able to insert the locking screws and everything should line up. A slight gap is okay and expected between the quad toprail and the receiver. Hope this helps!
EDIT: DO NOT forget to tighten the locking ring whe n it is all lined up. PICTURE 2 looks about right GAP WISE but you can look in and see the barrel nut is not indexed and the locking screws will cant the quadrail if you put them in. |
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First off, make sure you have the barrel properly inserted into the upper receiver. The barrel nut then goes over the barrel and attaches the barrel to the upper receiver. (I forgot to do this once and scratched up my upper. Oh well.)
Now is the time to position the barrel nut so that the gas tube can be inserted. You have to move the barrel nut left or right so that the holes line up for the gas tube. The barrel nut should be tight against the upper receiver. Next, the YHM instructions tell you to back off the lock nut from the barrel nut by 1 1/2 turns. You then screw the quadrail on to the barrel nut. At this point, I usually take an AR15 carryhandle and attach one end to the upper and the other end to the quadrail. Because your upper is the point of orientation for your scope and everything else, this will help you make sure the rail on your upper is in line with the rail on your quadrail. At this point, I usually reattach the front sight base and gas tube (but do not insert the pins in the front sight base yet). Using the YHM special wrench, you then tighten the lock nut fimly against the quadrail. Next, insert and tighten the two anti-twist screws into the right and left side of the quadrail. If you have followed the above instructions, the holes in the quadrail should be aligned with the slots in the barrel nut so that the anti-rotation screws may be inserted. I usually put Loctite Blue on these screws to make sure they do not work loose. You then can drive the pins into the front sight base and attach the flash hider and crush washer. Good luck mate. |
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