Replacing Front Sight Gas Block on Colt 6920

[GunDudeUSA]

Planning to replace the front sight gas block with a low profile gas block on my Colt, and put a longer rail over the barrel.

Can I use any low profile gas block, or is there a specific type that is needed for the replacement? I read something about gas blocks potentially moving, creating mis-alignment etc.

 

[smokebomb]

Re: Replacing Front Sight Gas Block on Colt 6920

There are several types of low profile gas blocks on the market. Some can use your existing pin holes. Some utilize set screws, these can potentially shift if installed wrong. With the set screw type you need to mock them up and drill a couple small dimples in the barrel so the screws have something to index to. Another option is clamp style gas blocks. These have screws that literally clamp the block onto your barrel.

Of these, I personally prefer the clamp styles if they clear the rail you intend to use. Some rails have very little room and with those you'll need to be careful which gas block you purchase.

Good luck, hope that clears up a little.

 

[smurph]

Re: Replacing Front Sight Gas Block on Colt 6920

There are also different size gas blocks, you will need to know the diameter of the barrel where it mounts.

 

[smokebomb]

Re: Replacing Front Sight Gas Block on Colt 6920

SHOULD be a .750 diameter block

 

[blackblue]

Re: Replacing Front Sight Gas Block on Colt 6920

You can also just cut your sight down.

 

[GunDudeUSA]

Re: Replacing Front Sight Gas Block on Colt 6920

C2, do you mean these for clamp-on?

Daniel Defence Low Profile Gas Block Clamp-On
http://www.midwayusa.com/product/245666/...ter-steel-matte

 

[slothlacrosse]

Re: Replacing Front Sight Gas Block on Colt 6920

For $38, ADCO will shave your FSB down so it will fit under just about any handguard.

I had them do it to my Mk18. Cheaper than a new gas block and it's not going anywhere.

 

[SmimL7]

Re: Replacing Front Sight Gas Block on Colt 6920

I would remove the FSB and save it in case you want to return the rifle to its current state. Clamp on gas blocks are cheap enough.

 

[Jay5oh]

Re: Replacing Front Sight Gas Block on Colt 6920

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SmimL7</div><div class="ubbcode-body">I would remove the FSB and save it in case you want to return the rifle to its current state. Clamp on gas blocks are cheap enough. </div></div>

X100

The A2 pinned on FSB is unique to that barrel. If you later decide to go back to a A2 style you will have to buy a new FSB and have someone drill it and the barrel for pins.

Buy a low profile set screw gas block, they are cheap. If set screws make you worry, red locktite/rokset them and stake them.

 

[scudzuki]

Re: Replacing Front Sight Gas Block on Colt 6920

Once a barrel is drilled and reamed for tapered pins with an FSB it cannot be adapted to another GB or FSB with tapered pins; they will never line up with the original holes.

Remove the original FSB and install a low profile GB with setscrews... the gas hole in every GB or FSB I have handled (and I've seen quite a few) have the gas hole opened up enough where it meets the gas hole in the barrel to accommodate a bit of misalignment without choking off the gas.

Shove the GB back against the HG cap or the shoulder, clock it in (make it point at 12:00) and snug the setscrews, then loosen the setscrews and remove the GB.

Use a center punch to mark the barrel in the center of the 2 little circles left by the cup points of the setscrews, then use a 3/16" drill to dimple the barrel to the depth of the drill point, that is, until the drill enters deep enough to reach full diameter, at those 2 locations.

Re-install the GB with a little blue (removable) Loctite in the setscrews.

It will NEVER move.

Joe