AR free float install

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Dryft

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Hey y'all,

I recently acquired a nice AR that I'd like to do some work on - but could use some advice:

1. It's got standard carbine handguards and a f-mark fsb.

2. I want to put a Troy Alpha rail on and will need a low profile gas block.

3. What do I need to look for in a low profile gas block? Obviously I will have to remove the existing sight - but what do I need to look out for in fit and installation ease?

4. The Alpha rail uses the existing barrel nut, but what do I do about the Delta ring?

It should be painfully obvious I am new to working on an AR - any and all recommendations or suggestions would be very welcome!

Thanks in advance.

Dryft.
 
Dryft said:
3. What do I need to look for in a low profile gas block? Obviously I will have to remove the existing sight - but what do I need to look out for in fit and installation ease?

-Make sure it's the same diameter as your gas block journal on the barrel. Example. Gas block journal diameter on barrel is .750" (pretty standard) you will want a gas block with an inside diameter of .750". I personally like the clamp screw style gas blocks as they don't mare the barrel (won't be seen but it bothers me). I also have used set screw style ones and they work just as well.

4. The Alpha rail uses the existing barrel nut, but what do I do about the Delta ring?

-Remove the barrel nut from the barrel. Remove the snap ring that holds the delta ring assembly. Reinstall the barrel nut less the delta ring assembly and properly torque to (30-80 ft-lbs). Make sure the gas tube can slide between the grooves on the barrel nut and into the receiver without any resistance. I put some anti seize on the receiver threads as well as the barrel nut.

-Installing the gas tube on an A2 FSB is really easy when it's off the gun. Not the case with a low-pro gas block. I usually slide the gas block onto a portion of the barrel and tighten it down. Then I install the gas tube and drive in the roll pin. After, remove the gas block and position it correctly on the barrel.
Click to expand...

Hope this info helps. Once you do this a couple of times it becomes second nature and the build times decrease significantly. Just go slow and watch a bunch of videos on Youtube to get your bearings.

Forgot to mention. Make sure you have the proper tools for the job.
-Receiver vise blocks
-AR-15 Armorer's wrench
-Punch set
-Hammer
-Torque wrench
-Allen wrenches
-Anti seize
 
Last edited:
GCMkc pretty much summed it up. And, I keep that AR15.com thread bookmarked in case I need a quick refresher or picture.

The Alpha Rail is a pretty easy install. The front sight base/gas block swap is the hardest part. You'll enjoy that handguard when you're done!
 
The Troy rails are meant to be easy to install. If you have a dremel tool, it's so easy a caveman can do it. You don't even need to swap out your gas block, if doing a little grinding doesn't scare you. You can chop down your existing gas block (google "chopped gas block" for instructions), cut the D-ring, weld spring and snap ring off with the dremel, and install the rail. You can do all of the work on your kitchen table if that suits you. A chopped gas block is a good option because the taper pinned connection to the barrel is as strong as it gets.
 
Get a railed LP gas block, they are cheap and add a little functionality for roughly the same price. If it were my gun I would change the barrel nut and add a true free float thread on tube.
 
Railed gas blocks aren't low profile. Low profile generally implies that a gas block will fit under a free floated handguard. Also, railed gas blocks are terrible wastes of space. If you want a sight attached to your barrel, there are lighter and mechanically simpler ways to do it. Also, using a railed gas block really limits your options.
 
You could always take the Dremel to the front sight, cutting off the tower and smoothing/rounding it. Shoot and bake on some Brownells Molycoat and Bob's your uncle.

You can make it very low profile.

One advantage is that the barrel is already cut for those taper pins and works perfectly with that gas block.

It is also cheap.

Once the modified block is under the railed handguards, you'll never notice any imperfections in the conversion.
 
f you want a sight attached to your barrel, there are lighter and mechanically simpler ways to do it.
Click to expand...

Plus, if he got the Alpha Rail with the flip up front sight, he's already got it taken care of.

That's an interesting gas block. I don't have the specs in front of me, but I'm not sure that 0.28" is enough room for the Alpha rail.
 
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