View Full Version : Gas block rail on ar15

January 4, 2013, 10:08 PM
Ok I have a bushmaster v-match ar. It's the flat top a hand no front rail. I got a quad rail gas block. Finally got it on. Pain in the ass I tell ya. But my question is (and I've looked elsewhere) how to match the hole in the gas block up with the hole in the barrel. I read its just an eyeing type thing. I butted the block up against the thicker barrel diameter under the free float hand guard. And lined it up from side to side as close as I could. I know the gas block hole is much bigger than the barrel hole too. What can I expect if it doesn't match up?

January 5, 2013, 01:18 AM
If it doesn't line up fully, your spent casings will either eject at 1-3 o'clock, or won't eject at all.

Best way is to use a level to get the upper receiver flat, then use another on the gas block to make sure it is, too.