Yup, just passing on experience from the school of "bought the parts, then bought the parts that would fit together"...

The LaRue "should" fit under the Troy rail, hopefully somebody reading has one mounted and covered with a Troy.

http://www.laruetactical.com/larue-tactical-low-profile-gas-block-lt-202

But, I'd bet it will hit a Noveske NSR, or other low clearance rail.

Not as sexy, but about guaranteed to clear anything you mount over it:

http://www.amazon.com/Troy-Profile-Rifle-Block-0-75-Inch/dp/B003RCBQSI

This is another popular one that covers the two front sight tower base contact points on the barrel, that are sometimes left unfinished. It will go under an NSR, but strikes the inside of the rail:

http://www.amazon.com/gp/product/B0...IKX0DER&pf_rd_r=01NJFBRSVVE6KQK6AZS9

It is labeled and sold as "low profile", but may not work with the newer thin tubes. There is another version that has a full lug along the top, it's thick and hits the gas tube channel.

Clamp-on: "usually" have a thicker base, also can hit in the Noveske, had one that didn't fit in a Troy Alpha, but did clear under a different Troy rail.

http://www.amazon.com/Yankee-Hill-M...33&sr=1-1&keywords=yhm+gas+block

What is the barrel brand, and do you know if the front sight base (FSB) has friction pins, or peened taper pins?

Last edited by AH64guy; 04/23/14.