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Just changed my gas block!

1492 Views 9 Replies 5 Participants Last post by  Aussie Arms
After posting a reply to Aziator in a different thread about taking an hour to plan and 5 minutes to do it, I decided to take the bull by the horns.

I followed the directions to remove my barrel and took out the operating rod. I have a set of plastic jaw covers for my vice and the bare barrel was easily clamped horizontally. I had previously replaced the stock Flash Hider with a Primary Weapons Systems combination muzzle break and FH which needed a 5/8 wrench to get off. Naturally I couldn't find any of my 5/8" wrenches so I had to make do, carefully, with a small adjustable wrench. Next the gas block - it had a small locking screw holding it in place which was easily loosened with a 5/32 allen wrench. After that it slipped forward with a minimum of twisting and pulling. I had been wondering how to position the new gas block, but the barrel and the gas block were keyed so no mistakes could be made (well, actually I guess you could put it on 180 degrees wrong just based on the key and slot, but the barrel has a dimple where the lock screw contacts it to make it even more obvious). Installing the new gas block was easy since it was also keyed. I did have to apply a little force to get it completely tight against the barrel shoulder and used a little loctite on both the FH and lock screw.

Next up was the new piston head. The old piston was clamped tightly and the head came off with quite a bit of torque required. It did appear to have some sort of locktite on it, so I put some on the new head and screwed it in tightly.

Putting everything back together gave me a little consternation because I had pulled out the gas tube to look at it and discovered that it has the gas holes in a line down the tube. The tube itself has slots which key to the gas block but it could be installed with the holes facing up into the top rail or down into the bottom of the receiver and I didn't notice which way it was oriented when I pulled it out! I installed it with the holes facing downward for now, and put everything back together. A quick function check and I was finished in a little over 10 minutes (at least half of which was spent looking for the 5/8" wrench and agonizing over the gas tube orientation).

All in all it was an easy swap since I had the vice and plastic jaws. It would definitely be a PITA to swap the piston heads if you had the old gas block on your rifle and the new one on a conversion kit. But now I'm set up and waiting for my 7.62x39 conversion kit.

To finish up, anybody want the old gas block as a spare? Also the picture on the RobArms website doesn't show the orientation of the holes in the gas tube - does anybody know which way it's supposed to go, up or down?
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Take a look at their videos on the RobArm web site. It says to put them in one way for dry dusty conditions and the other way for some other reason. It will tell you there!

Good Job!
How do you like the PWS brake? Mine should be here soon.
I haven't gotten a chance to shoot with the PWS brake/FH on yet. I also purchased one for my FAL and that's next on my gunsmithing chores.

I left off that the head was extremely tight on the operating rod and I applied a little heat with a match to the area the head was threaded into to loosen it up.

I didn't realize the installing the barrel video talked about the gas tube. The one I saw previously was different. Bottom line, the gas tube orientation isn't critical and I installed it right for my conditions.
You use the Peel split washer to find the position where the muzzle break is indexed to the top (The symbol I think is on the top) and it should work as advertised.

Here's the PWS piston upper with their muzzle break attached. Sweet!

I didn't realise how much technology and design has gone into these muzzle breaks and how they are designed for each type of weapons system and each caliber.

Remember, these are not classed as a flash suppressor, they are a muzzle break first with some flash suppression. I'm looking forward to mine too!
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That is one "Bad Ass" lookin' muzzle break! Let me know how it works out. ???
Cool, muzzle break with small VORTEX on the end!
You use the split washers to find the position where the muzzle break is indexed to the top (The symbol I think is on the top) and it should work as advertised. 
Actually it's not a split washer, it's called a Peel Washer.  This was the first time I have ever come across such a thing.  You heat it up and delaminate a small thin slice at a time until you wind up with just exactly the thickness washer you need for the brake/FH to line up properly as Aussie said with the logo aligned straight up.

I used a match while holding the washer with a pair of pliers and then used an exacto knive to try to peel off the slices.  It was tedious and I'm tempted to measure the resulting thickness and see how hard it would be to machine down a fixed washer.  But when I took it off to get the old gas block off, it was still in one piece so I reused it.

Interestingly, the one that I have for my FAL came with a crush washer instead of the peel washer.  I don't know why the difference except some of the silencers with QD mounts mention needing the FH to have a peel washer - presumably to ensure a square surface to mate against.
So many Toys....... so little money ;D Give us a range report. Thanks.

Thank you for correcting me on the washer name. I wasn't feeling too well when I posted that :-\

I have since corrected my post ;D

Another shining example of "back up" coming to the rescue!
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