Gas block rail on ar15

psychohellbilly666 · 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?

Ridge_Runner_5 · 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.

January 4, 2013, 10:08 PM	#1
psychohellbilly666 Senior Member Join Date: May 12, 2009 Location: Princeton, IN Posts: 320	Gas block rail on ar15 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	#2
Ridge_Runner_5 Senior Member Join Date: February 8, 2008 Location: Denver, CO Posts: 1,925	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.