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Posted: 3/1/2009 7:25:34 PM EDT
Hey guys, I'm new to ar15.com and ar's all together... But I recently purchased a Double Star, put an A3 upper and Surefire quad rail system on it along with an EO Tech 555... But I want to put on the Troy BUIS pair deal that just came in from Denny's/ Global Tactical (which had great customer service btw, props to Denny), so I bought this quad rail gas block... Well, when I line the gas block up with the rail system, the gas block's top rail sits a little lower than the rail. I was wondering if this will create problems when putting the Troy front sight on it. Should I buy a free float and put the front sight on that? Or go ahead and mount it on the quad rail gas block that is about 1/4 inch lower than the rail? BTW, I have a 16" barrel and if I purchase a free float, what length should I get to cover the low profile gas block? Thanks for the input 
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| First post and no repsonse, well I'll take a shot. The Troy BUIS pair are designed to work from the same rail height. Look at a Noveske low pro upper or S&W M&P 15T rifle which both utilize the Troy BUIS for factory install. If your new gas block is 1/4" lower than your upper rail, this BUIS setup will not work and you will be shooting WAY high. How to get the front BUIS up higher can be done several ways. A new full float rail with low profile gas block would certainly work but I would try to find a gas block with a higher rail that matches your upper rail as a cheaper alternative. Or sell the front BUIS and keep your fixed A2 front as is. |
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Railed gas blocks are generally lower than rails and designed for specific fixed or folding sights and IMO a waste. A FF rail 2" longer than your current set up will be what you want to cover a new LOW PROFILE gas block. Since your gas block will be smaller and the rails aluminum it will be lighter than the steel 4 railed gas block as well.
My rifle is a carbine gas systen with midlength 9" rail... you could also use a longer rail if you like. Lots of people like 10" or even 12" rails with your barrel length. Here is my 9" with Troy on a carbine gas system. 
Troy makes a FF 10" that looks similar to mine for $240 if you want to be able to install/remove the rail yourself, have a continuous rail, and FF but any 9" or longer rail will work. Generally speakiong each additional inch for an aluminum quad rail adds 1-1.5oz per inch. This gives a longer sight radius and allows the bipod or light to be mounted more forward as well as less exposed barrel to burn you when dropping on a sling the rifle to transition to pistol. The cheapest way to have a good low profile gas block is to reinstall your current standard front sight and cut off the bayonette lug, sling mount, and front sight tower.. then moly coat everything with Norells or Guncoat or just cold blue and CLP the crap out of the gas block. |
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