Gas piston - hard to get out?

[twinhairdryers 2]

Ever since I have had my S-12 it shoots high brass rounds on 1 gas setting fine. Anything over 1200ft/s shoots fine. Switching to #2 doesn't help cycle much of any low brass stuff at all. I tried for about 3 hours to get my gas block off to drill out my gas ports to no avail. I then have noticed that the 3/4" gas piston just behind behind the adjustment screw on the end of the gas block is very tight in the cylinder. I have to hammer it out with a wooden dowl from the bolt side just to clean it. Is this normal? It seems the end of my gas tube is tapered so the piston stops just about 1/4" before the gas holes from the barrell into the gas chamber. Is this the correct design, or should I get out the dremel and polish this whole area within the cylinder before I send this thing in to get the gas ports drilled out?

 

Also, who is a reputable place to send a S-12 to these days to have a gas block removed just to drill out the holes? I thought I could do it myself, but was worried I would damage my barrell getting the thing off.

 

Today I hit the 1800 round mark on the S-12 and finally tore through one of the green buffers from blackjack. A testament to his parts. I will post some pics. You can see every outline of every high impact surface for hundreds of rounds. I switched to the black one until I can shoot lighter loads in this thing.

 

fun times.

[dinzag 31]

It should slide back & forth when you tip the gun.

You should be able to hear it go clunk-clunk.

Try polishing the O.D. of the piston and the I.D. of the cylinder it rests in with steel wool or 400 grit sandpaper. With that many rounds through it you would think it should be broke in, but perhaps it's been stuck for awhile.

 

As for the gas block, once the pins are out, try driving it forward with a brass punch and hammer.

If it's stubborn, put a little heat on it. I've seen some sticky ones, but not a single one couldn't be removed. I usually polish up the press surfaces with steel wool or 400 grit sandpaper before reassembly.

 

The barrel is pretty stout on them puppies & it's very hard stuff.

 

As for the gas ports, just get a cobalt drill bit and drill slow & easy. You need to be careful of the bit snapping off in there. The other trick part is trying to get the burrs out of the inside of the barrel.

 

I drilled mine due to lousy performance with cheap ammo. I think I opened them up with a 3/32" bit. Runs great now. Polishing the FCG improved mine some more, but at 1800 rounds, yours should be nice & worn in.

[doug01 3]

I dom't know what dinzag just said but he know;s his sit and u should listen. My balls are being tusseled as we speak.

[random sylvester 0]

your piston should come out fine , try this ,

remove gas adjusting screw , tilt gun back (bbl pointing up) push piston back with finger if u need to,pull bolt back a little or all the way and release , piston should fly out and smash the wall in front of you

[6500rpm 670]

Mine has plenty of use and cleaned every time I shoot it, the piston moves free in the bore that it operates in, but I pretty much have to drive it out through the threaded end of the gas block, but not with so much force that I'm worried about the threads. With the handguard off and a short soaking w/ penetrating oil

I was able to drive the gas block off with a brass drift working around the block so it doesn't bind. The first 1/4" it the worst, after that it frees up pretty quick. A press would be a better idea if you have access.

With the gas block plug out, can you see all 3 or 4 holes drilled through to the barrel. There was a post a while back where the holes were drilled way off center and only had 2 exposed pass throughs to cycle the action.

[twinhairdryers 2]

I think i'll try some light sanding polishing on both parts and see if it makes a difference. It seems that it takes quite a bit of force just to move the piston back towards the bolt from the gas port area, likes its stuck for a while. If I get this moving better in the cylinder I may not have to drill the holes out.

[Bvamp 604]

mine was like this, before I cleaned my s12 for the first time. If you longer members here may recall, I intentionally didnt clean my s12 for about a year and a half, to see what would make it misfire.

 

my gas plug piston, piece of metal, whatever, was in there pretty damn good when I finally removed it. what I did was took a hammer to a cleaning rod to ram it out of the gun, via the gas tube. it took some effort, and some PB blaster, but it came out, finally.

 

my light load jamming problems were occuring due to a loosened operating rod on the bolt carrier, probably from mixing various rounds on the light setting #2. I sweated solder into the threading joint on the bolt carrier, which solved the problem temporarily, but the stuff didnt stick, as I thought it wouldnt. so I need to weld it, or press the bolt carrier joint again in a press. havent really pursued it to the final point, because I dont know if a weld will stick to the chrome on the op rod and the steel on the bolt carrier. the two machinists Ive asked said it wont hold.

 

make sure you have all the burnt crud build up off the piston itself and the gas block before you sand anything.

[twinhairdryers 2]

So i'm back at the gas block removal. It has moved maybe a 16" using my limited tools of a brass punch to drift it out after removing the two front pins.

 

I did notice something for the first time. There is a hole through the gas tube, on the bolt carrier side (not the gas piston chamber a bit larger in diameter than the two pins I removed in the front end of the gas block. I'm assuming this is normal, correct, some sort of regulator hole for the gas on the bolt side? If this shouldn't be there, i'll just plug that hole up and it may be the source of my low brass ejections on #2 setting. Hell, it would be worth a try at least. The hole is on the left side of the gas tube (opposite the breach side).

[Cobra 76 two 2,677]

That's normal, won't do any good to plug it.

[twinhairdryers 2]

After two bent up brass punches, I got out a 6" x 1/2" diam chisel and a small sledge hammer. Finally got the gas block off after about 10 minutes of whacking away. If you don't have a press or vice or fancy tools, you can't be concerned about dinging your finish in this process. Mine came out clean in the end with even a couple minor mis-hits with the big hammer. Got the titanium drill bit out, expanded the gas holes in about 5 minutes time, the dremmel and polished the inside of the gas block and gas piston outside, and slammed it back together. I added a pic of the finally drilled holes after 3 hours of fooling around with the wrong tools in previous attempts. This time it was an hour total to do the entire job.

 

http://i14.tinypic.com/40o40us.jpg

 

I also included a pic of the mystery hole in the side of the gas tube I inquired about.

 

http://i13.tinypic.com/4dfg9wz.jpg

 

I also added a pic of the finished S-12 since I haven't posted in a while and added some do-dads.

 

http://i13.tinypic.com/2yty92e.jpg

 

I added some pics of Cobra's novel glock rear sight idea. That project was about 20 minutes time, very simple to do, and my groups are 3" to the right of center at 50yards all day with slugs. It uses the Rusmilitary clamp on AK front sight and a trimmed up Glock 17 rear sight punched into the factory rear sight stand. This turned out better than I ever expected. Thanks Cobra!

 

http://i14.tinypic.com/4bxwfnb.jpg

 

http://i14.tinypic.com/4dg45ew.jpg

 

http://i13.tinypic.com/2hxvogm.jpg

 

 

We'll be testing the low brass cycling this weekend! I have a case of #7 Wolf and some #8 dove loads on the very light side.

[TPABA 0]

Today I hit the 1800 round mark on the S-12 and finally tore through one of the green buffers from blackjack.

 

You count the shells? With a Kalashnikov weapon, you don't count rounds, you count wars.

[twinhairdryers 2]

Here is the new range report after drilling my ports to 3/32 x 3 (and reaming them just bit larger than 3/32 manually). I headed out to my favorite shooting range, about 5 miles off shore on the gulf of mexico. Very peacefull, no ROs, no hunters muttering street sweeper, no slug only rules, no problems other than steadying a shot on milk jugs in heavy seas becomes a great training experience! I will never be a coast gaurd sniper for damn sure.

 

#1 gas setting only:

 

50 rounds of of wolf #7 sport shot loads, low brass - 0 FTF/FTE's

 

25 rounds of Fioccochi #8 dove loads, low brass - 1 FTF/0FTEs

 

15 rounds of Speer lawman 00 buck - 0 FTF/FTEs

 

25 rounds of Estate cartridge #8 game loads - 0 FTF/FTE's

 

15 rounds of 3" mag remington slugger slugs - 0 FTF/FTE's 1 sore sholder

 

Water jugs 0-15 w/l fun factor 9

 

I think my gas problems are solved. Never even thought of moving to the #2 setting. The one FTF I had was with my 5 round mag I trimmed the follower one so it is a 6 rounder, and is not 100% reliable on any loads.

 

I would recommend any novice gunsmiths attempting to loosen their gas blocks use a very large hammer and heavy stell punch or chisel. And don't be concerned about breaking the gun or nicking any finish off it. It seems pretty bullet proof. If you take too much care to to do this job it will take you several hours or days. If you have a heat source or press, use them. I didn't. Use a sharp titanium drill bit and drill with low pressure. It would become a difficult job if you broke a bit into a gas hole.

 

After all that hammering on that gas block, that glock rear sight stayed put and is straighter in windage than before (was 3" off center @ 50 yards before). got lucky getting everything back on straight.

 

Oh yes, and as danzig mentioned. after a 400grit and dremmel polish if the gas piston, when i rotate the gun you hear the piston slide back and forth. it never did that since it was new, nor after 2000 rounds. the inside of the gas chamber was rough and slightly pitted, used to hang the piston i think. another good idea to try even before drilling your holes if you are on the edge of an occasional FTE with low power shot shells.