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Lazerrus
06-13-12, 17:06
Hi all. New here and somewhat new to AR's also. I have a Doublestar lower with a S&W M&P upper with a 7" Troy quad rail. I want to install a longer rail. I believe I have to change my gas block to a low profile block in order for a longer rail to clear past it. What do I need to know in order to do this. Thanks for any and all help.
AR15barrels
06-13-12, 17:23
Not much to it.
Just un-bolt the existing parts and re-install the new ones.
As the new rail is going to cover the low profile gas block, make sure the rail you purchase will slide over the low profile gas block as you generally need to install the gas block before the rail if the rail inhibits access to the gas block's screws.
SteveL
06-13-12, 17:25
There are several things you can do. You can leave your gas block as it is (I'm guessing it's a standard front sight post) and use a rail from DD or Centurion that has a cutout for it. Or you can shave down the existing front sight post and go over it with any long rail. You can either do this yourself or have a smith do it for you. There are video tutorials on YouTube. Or I guess you could replace it with a set screw or clamp on type low profile block. This would be the least desireable option I think.
Lazerrus
06-13-12, 17:33
Not much to it.
Just un-bolt the existing parts and re-install the new ones.
As the new rail is going to cover the low profile gas block, make sure the rail you purchase will slide over the low profile gas block as you generally need to install the gas block before the rail if the rail inhibits access to the gas block's screws.

Thanks. I wasn't sure if the gas port hole in the barrel came in different sizes etc.
Lazerrus
06-13-12, 17:35
There are several things you can do. You can leave your gas block as it is (I'm guessing it's a standard front sight post) and use a rail from DD or Centurion that has a cutout for it. Or you can shave down the existing front sight post and go over it with any long rail. You can either do this yourself or have a smith do it for you. There are video tutorials on YouTube. Or I guess you could replace it with a set screw or clamp on type low profile block. This would be the least desireable option I think.

Thanks Steve. And love your avatar! I am huge ALIEN fan and collector. I had noticed the Daniel rails with the cutout. I am looking for the new rail to be fde so I was just going to get another Troy.
AR15barrels
06-13-12, 17:37
Thanks. I wasn't sure if the gas port hole in the barrel came in different sizes etc.

The hole in the barrel DOES come in different sizes, but the gas blocks all have LARGER holes than the barrel hole so you don't need to be concerned with the size of the hole in the gas block so long as you align the hole in the gas block with the hole in the barrel when installing the new gas block.
SteveL
06-13-12, 22:53
Thanks Steve. And love your avatar! I am huge ALIEN fan and collector. I had noticed the Daniel rails with the cutout. I am looking for the new rail to be fde so I was just going to get another Troy.

You're welcome and thanks.

Also take a look at the new Noveske NSR rail. There's a thread about it here (https://www.m4carbine.net/showthread.php?t=97477).

The rail itself is black, but it looks like alot of the upcoming polymer accessories will be available in FDE.