How difficult is it to change the gas block on an AR?


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mugsie
July 3, 2007, 08:48 PM
I have a Bushy in A3 configuration, the handle disengages but the front sight does not. How difficult is it to remove the front sight / gas block and replace it with a gas block for a flat top? Am I making sense here? I'm not too sure of the terms. It seems as though I just have to knock out the two pins and the one roll pin and it all removes once I remove the hand guards. Can I use the same handguards or do I need a different configuration? What am I getting into here? :confused:

Thanks everyone....

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Bartholomew Roberts
July 3, 2007, 09:27 PM
You have to slide the front sight base over the muzzle of the rifle. So you'll first need to remove the muzzle device and then it will be as easy as knocking out the roll pin, knocking out the two pins and sliding it off.

In practice, knocking out the FSB pins can be a bit of a pain, especially on a Bushmaster. When I removed my Bushy FSB, one pin dropped right out after I gave it a good whack with a rubber mallet with some wood supporting either side of the FSB. The second one took about four hours to remove. We ended up cutting away all the FSB metal underneath with a dremel and then bent a Starret steel punch in a drill press trying to push it out.

koja48
July 3, 2007, 09:33 PM
Never took mine apart, but did research the process. Pins are tapered (so drive out from the small end). Brownells makes a concave punch just for this purpose. If you flatten the end of the pins, they become rivets & must be drilled out. Once the pins are out, it takes a few sharp blows with a rubber mallet to break the sight frame loose (finish was applied AFTER the unit was assembled). Good luck; I'd like to put a flip-up front sight on mine, but haven't quite become inspired yet.

Bartholomew Roberts
July 3, 2007, 09:37 PM
Yes, drive the pins out from left to right (punch goes on side of rifle with bolt catch and no ejection port). However, it isn't quite as simple as it sounds despite that. Bushmaster is known for drilling fairly deep into the barrel. In my case, there was enough of the barrel suporting the pin that cutting the FSB out was practically pointless since it still had about 80% of it surrounded by metal.

I forget what we finally did to break it free; but some have tried freeezing or heating with some success. I didn't have to drill them out; but the pins in mine were tool steel. Drilling them out with the tools and skills I posses would not be possible without damage to the barrel.

DMK
July 3, 2007, 10:08 PM
Weird, I've removed the FSBs from 9 barrels to refinish them with Gunkote. Two were Bushies, three Colts (all used, two were milsurp), two RRA and two CMMG. Never had any trouble getting the pins out. I use Kroil liberally and soak it overnight before even attempting it. Fixed the barrel tightly in wood blocks in a vice so it won't move and used regular punches, starting it with a cone shaped punch.

Bartholomew Roberts
July 4, 2007, 12:42 AM
I've done two Bushies since then and neither one was that bad. But they did require a little more effort than most of the other brands I've messed with.

nvshooter
July 4, 2007, 02:44 AM
Getting the front sight off (the triangular kind) is a hillary, for sure. I had to pound like hell on mine-- even after the pins were out. I suggest you drive out the pins, then take your barrel to an autoparts store or a machine shop that might have a brake press and slowly press the base off. I only buy AR guns that have the setscrew block now...

koja48
July 4, 2007, 08:46 AM
LOL! Note to self: File this term away against future use.

DougW
July 4, 2007, 10:39 AM
Mounting a low profile of picatinny gas block is easy. I would suggest installing a new gas tube too. If you plan on some sort of flip up front sight, a gas block like the Yankee Hill or DPMS work great. To sight in the front sight, you will need your allen wrenches at the range so hat you can rotate the FSB to properly "time" the front sight. If you plan on not using a BUIS system, mount the new block and go shootin"! :D

DMK
July 4, 2007, 11:19 AM
the handle disengages but the front sight does not. The question we should have asked up front is why do you feel the need to remove your front sight? It's not necessary. Your optics will not be affected by it.

Can I use the same handguards or do I need a different configuration?You may be able to, but it would depend on the gas block you use. The handguards are held on by the front cap. The cap is held in place by the gas block, which traps it against a step machined into the barrel. Some gas blocks are designed to be used with free float tubes and will fit up against that step, leaving no room for the handguard cap.

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