I'm trying to remove the gas tube in order to remove the barrel. I've driven the roll pin out which wasn't easy. Bent up two chinese punches driving it out. Finally cut off the bent end and now was able to drive out the pin.

With the pin removed, the gastube doesn't want to budge by hand. Any tips??? I DO need to reuse this gas tube.

Thanks in advance.

M4-AK

It is probably sooted up pretty good with carbon where it sits inside the front sight housing. Spray some lube inside the hole it goes in, I use Kroil. Next take a set of vise grips and *GINGERLY* set it to where it just firmly grips the gas tube, but does not crush or pinch it. Start turning it side to side so as to break the bond with the carbon. After it starts to turn easier, pull the tube back towards the upper. Sometimes you can simply take a rubber mallet and hit the vise grips easily to remove it.

So far, yes there is lots of carbon. I've had no luck with vice grips getting it to budge. I'm afraid I may have to bugger up and replace the gastube to get it out.

Any other suggestions are welcome.

M4-AK

Okay this morning used big vice grips and was able to get them tight enough to twist the tube. So far the tube is a little scraped up but not bent. I can twist it but it still ain't a coming out. Even with tapping on the vice grips.

Next suggestion please.

M4-AK

I’ve never done this, so I’m making a totally irresponsible suggestion, but maybe heat the sight tower while holding something cold against the gas tube while trying to get the tube to move.

Expansion, contraction, you know!

Maybe try heating the whole thing and see what happens?  Try tossing it in the freezer (if it’ll fit) and see what happens!!

Brownells sells a gas tube removal tool that will give you a better grip on the thing.  They also sell replacement gas tubes – dealer price IIRC is something like $8!!

I’ve heard of folks accidentally breaking the gas tube off where it enters the tower.  They can sometimes be frozen in that solidly!!  You may be getting a new gas tube whether you like it or not!  [:D]

However, since it moves a little bit, I’d first be inclined to just soak it in Kroil or a similar penetrating oil and periodically wiggling it a bit.  I suspect in a few days it might start to loosen up.

How about tying it to the lawnmower next time you do the grass and see if that vibrates anything loose??  OK, maybe I’m getting silly!! [:E]

Don’t know if any of this helps – good luck!

You have a vise handy? I've done this several times without screwing up any gas tubes.

First start by inverting the upper so the gas tube is facing towards the floor.

Next, find the slight bend in the gas tube and snug that section in the vise jaws. The bend in the tube keeps the upper from flopping right-side-up. Tighten until the upper is fully supported by the tube.

Grab a tool with a plastic handle (like a large screwdriver) and give the rear of the upper receiver a few quick raps.

The gas tube will remain stationary and the upper will begin to slide off. If the gas tube begins to move with the upper just tighten the vise a tad more and repeat.

Stumbled on this method after screwing up a couple of gas tubes with pliers and vise grips.

Why, if you don't mind my asking, are you taking off the gas tube?

It's maintenance free.  Are you having function problems?

Yes, I've got a slight windage issue and want to reindex the barrel....

Thanks

Automatic Trransmission Fluid is very good at disolving carbon.

Vise-Grips and twisting/tapping have always worked for me.

go te Sears and get the roll pin punches before you put it back together.

use anti-seize on the threads of the barrel nut when you re-torque the barrel.

If your going to re-index the barrel why not drive the front site base pins out and slide if forward.

Mark your pins, both for front and rear and for orientation and your site base should line back up.

The Bushmaster gas tube wrench really works. It's a vice for the tube.

As for barrel indexing. My original problem. Has anyone encountered a rear sight aperture thats not centered? I mean the hole is drilled slightly to one side.?

M4-AK

No.  But my A2 rear sight assembly twists about 2 degrees to the left of center.  I think its just due to sloppy tolerances and the spring being on the right side pushing it to the left.  You can rotate it back to center, but the spring rotates it right back to the left.  Bushmaster told me this is normal.

yes thats normal. Accuracy speaks and others sell a sight that stays put. Theirs has a bump welded on one side that keeps it cocked straight. Others drill a hole and put a pin in it. But all say it's no problem. Just a psychological thing.

M4-AK

It's only noticable on A1 "L" aperatures, though A2's are also offset (.007" IIRC) to compensate for it's pivoting on the windage screw.

[img]http://www.imagestation.com/picture/sraid5/p01ab13cd3c35db026b1a83c299761836/fe4b71b7.jpg[/img]

No kidding. I never knew that. So the pivoting compensation is for the windage screw, or the total twist of the rear sight?

M4-AK

gregw45's idea works real well - I've gotten a seriously frozen gas tube loose without damage. I don't try to tap it straight off, though. Just rotate (twist) the upper back and forth to loosen it up. The jag in the gas tube makes it impossible for it (the tube) to turn in the vice jaws. Also takes minimum jaw pressure - just enough to support the upper.

M4-AK - save those bent punches. Cut most of the punch off, leaving about a 3/16" length. Use these as starter punches first to break the roll pin loose. It is much harder to bend a short length. Just be careful it doesn't get wedged in the hole (on the tapered shoulder of the punch).