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Posted: 8/16/2012 12:06:08 PM EDT
I have a Colt 6920 that I'm considering modifying. I would like to have a longer quad rail, possibly free floated. I'm not crazy about the handguards that fit around the standard FSB, so it would require pulling it and changing to a lower profile gas block. It's my understanding that the factory pinned FSB is the most secure set up you can get. Is it worth it to change it? I'm a little reluctant to cut it down, because it can never be put back to original.


Link Posted: 8/16/2012 12:14:18 PM EDT
i would take it off not cut it down. that way you can at least sell it. and get the money back for the gas block. i personally love how ff rails look. and the way you can use a foregrip and front flip up site makes for great co witness using optics. its just what your into some like too keep the standard handguards for less weight. i figure if you have 2 rifles its cool too do that but one i will keep a ff rail on it. prefer larue rails.
Link Posted: 8/16/2012 12:14:45 PM EDT
You're one of the few to not jump at cutting it down first(thank you).

After you tap the pins out and remove it, you can always get a clamping low profile block from Troy for about $30. Holds with two bolts, made of steel, and holds like a champ.

Otherwise you'll need to find a low profile block that uses pins OR get a set screw style one and possibly have your barrel dimpled so they hold.

Easiest, most cost-effective, and very secure is to just buy the Troy for $30.
Link Posted: 8/16/2012 12:14:55 PM EDT
[Last Edit: 8/16/2012 12:15:23 PM EDT by hallstar606]
double post
Link Posted: 8/16/2012 12:17:30 PM EDT
Vltor makes a nice clamp on gas block too. You could always see if Adco can pin a lo-pro in place using the existing holes. I do not know if that is possible though.
Link Posted: 8/16/2012 12:30:24 PM EDT
It`s true that once you cut the sight down it cant be returned to the origional but you can still just purchase another
sight if you wish to return it to origional....The low pro gas blocks are not quite as stable as the pinned sight...there
is a possibility they could twist a bit....but I haven`t heard of any of them failing

If you want a longer rail just do it....there are tons of people that have made that mod.. It`s my intention to do the
same thing as soon as I find a rail I like...I haven`t decided whether I`m going to cut the origional GB sight or get a
Low pro....I`d be happy to do either..Jim
Link Posted: 8/16/2012 12:57:35 PM EDT
Get this!! Longer rail no cutting!!

Centurion Arms C4 Cutout!!


C4 Carbine cutout

or this:

C4 FPS Rail System
Link Posted: 8/16/2012 3:14:01 PM EDT
Originally Posted By jimjc:
It`s true that once you cut the sight down it cant be returned to the origional but you can still just purchase another
sight if you wish to return it to origional.

It has been my understanding that the factory FSB is drilled at the same time as the barrel and is a 1:1 fit. A new FSB would be very unlikely to line up with the existing notches in the barrel as they are not standard or interchangeable. Am I incorrect?

Link Posted: 8/16/2012 3:25:02 PM EDT
[Last Edit: 8/16/2012 3:25:51 PM EDT by Mop89]
I replaced my gasblock/front sight assemply on my RRA with a low profile gas block and a 13'' Troy rail. Was fairly easy to do. Just get a set of punches and be patient.

Edit: RRA was clamp on, replaced it with a VLTOR clamp on low profile.
Link Posted: 8/16/2012 3:43:31 PM EDT
My suggestion would be to cut the existing site tower. The percentage of the chance of going back to the original is so low once you've railed it really isn't a factor in my book. The money saved could be used to buy a premium flip up site with no regrets.
Link Posted: 8/19/2012 1:29:51 PM EDT
Thanks for the suggestions. I guess another part of the question might be: "Is a free float quad on a 6920 a good idea?" Ever since I got my SR-15, I've really grown to like the longer handguard and clean sight picture with the BUIS flipped down. Anyone made the conversion on a 6920 and regretted it?

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