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jdeitch

Modification to repair FTE issues on Saigas with blocked gas ports

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Folow up:

took her out to the range today, was quite excited to test her out with all 4 ports showing and expecting a great run. NOPE, didn't happen. matter of fact it was much worse!

Would not feed the same ammo that she was feeding when shoulder firing prior to this mod.

Decided it was time to figue out what the @#%@# was going on.

my proceedures to diagnose:

1) check bolt travel when firing: found it was only half of normal stroke. WHY?

2) checked ejection by hand: seemed normal, but stiff. Took time to grease all contact points including bolt locking lugs, bolt rails, bolt and carrier bore, contact area of hammer. (new gun)

3) checked ejection by hand again, felt smoother so I test fired: shell caught on barrel shroud. (some improvement)

4) Removed extended bolt-on charging handle (to reduce bolt mass and reduce gas needed to accellerate bolt), tested: every 2nd round FTE

5) Removed gas plug and piston: checked for fouling of any kind, none found. ran gas plug in until seated and only 10 degrees trun to lock into setting 2 (factory plug)

6) loaded one round, removed magazine and test fired: ejected case about 3 feet from gun. Although ejection was complete it should have done so with more distance (I think). Obviously there is a lot of friction between bolt and next round. just seem to be short on gas.

7) Removed foregrip and inspected gas block for signs of leakage: only indication was from gas vent hole.

8) removed gas plug and piston and inspected op rod alignment in gas tube: seem to be slightly off center.( Closer to barrel in gas tube) I'm being very critical of alignment when I say slightly.

Began to wonder if gas block was not truly aligned even though gas block pins matched barrel grooves well. Using plastic hammer and 8 ounce hammer I installed gas plug until seated, placed plastic hammer against plug and set the 8 ounce in motion..I noticed the slight misalignment seem to disapear after removal of the gas plug.

I put her back together, loaded one round and removed the magazine.......ejected the case about 9 feet from gun. shot the next round with mag in and ejection was complete with the case landing about 8 feet from the gun.

The next 150 rounds went off with no FTE's and all cases landing 7-8 feet from gun with a large upward arch.....SWEET

 

Summary:

I think the issue was: the gas block was slighlty mismatched (even though the retaining pins went in ok) causing some binding of the piston and/or op rod in the gas tube!!

Edited by nitukamots
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I want to do this mod to my 3 port Saiga. It looks quite doable to me. I do have one question, how do I remove the rear sight to allow access to rework the hold into the "D" shape?

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I want to do this mod to my 3 port Saiga. It looks quite doable to me. I do have one question, how do I remove the rear sight to allow access to rework the hold into the "D" shape?

 

The hole for the "D" mod in the gas block has nothing to do with the rear sight, they are not even close in proximity. The front sight bead on a factory S12 is attached to the top of the gas block and is not in your way either. Once you remove the gas block, you will see the "gas window" inside the gas block. You should also notice a carbon ring around your gas ports in the barrel, this will give you a good idea of what ports are blocked, if any and where you will need to clearance the gas block to unobstruct those gas ports.

 

Follow the advice throughout this thread and its very easy to accomplish.

 

EDIT2; Why this is not a sticky yet is ridiculous. This thread and topic has so much useful and routinely discussed information in it, that it should be pinned at the very top of the S12 forum. Remove some of the outdated, obsolete stickies and replace with this topic!

Edited by Mullet Man
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I want to do this mod to my 3 port Saiga. It looks quite doable to me. I do have one question, how do I remove the rear sight to allow access to rework the hold into the "D" shape?

 

The hole for the "D" mod in the gas block has nothing to do with the rear sight, they are not even close in proximity. The front sight bead on a factory S12 is attached to the top of the gas block and is not in your way either. Once you remove the gas block, you will see the "gas window" inside the gas block. You should also notice a carbon ring around your gas ports in the barrel, this will give you a good idea of what ports are blocked, if any and where you will need to clearance the gas block to unobstruct those gas ports.

 

Follow the advice throughout this thread and its very easy to accomplish.

 

EDIT2; Why this is not a sticky yet is ridiculous. This thread and topic has so much useful and routinely discussed information in it, that it should be pinned at the very top of the S12 forum. Remove some of the outdated, obsolete stickies and replace with this topic!

 

i agree

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Thanks everybody. I looked things over again and I now think I have the answer. Looks like there's a hold under the hand guard I can't see with the gun assembled. It's the hole you have to go THROUGH to get to the hold that needs the "D" mod done to it. Feel a little silly,

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Thanks everybody. I looked things over again and I now think I have the answer. Looks like there's a hold under the hand guard I can't see with the gun assembled. It's the hole you have to go THROUGH to get to the hold that needs the "D" mod done to it. Feel a little silly,

 

 

scratching_head.jpg

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I have done a very similar mod to this. One of my ports was just BARELY blocked. I opened the ports up a bit with my drill press, and opened the hole in the gas block with a drill bit that was just slightly larger than the current hole. You'll notice that the gas port hole is smaller than the hole that you go through to reach it. All of my ports are now easily visible.

 

STICKY this awesome thread please!

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Followed this guide to enlarging my gas ports and it made an incredible difference. Could not previously get 71/2 Federal loads to eject. I have a 4 port barrel and 2 of the ports were partially covered and all 4 were undersized. I drilled out ports to .070 and opened the gas window to 11/32". I had one of those gas blocks that were difficult to get off but eventually it gave. Roll pins were easy to remove, you just have to remove them from the correct side. No problem firing cheap federal loads now. Thanks for the tutorial.

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My gas block was not to bad to get off and I also have a vodka 4 holer guess I will drill out the 4 ports and oversize the gas window, I am also going to run a tac-47 plug ....any advise?

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I am assuming you are having problems with some ammo. Check to see if any of your 4 ports are blocked before you drill the gas window larger. Also check the port size before drilling. I read from a previous post that .070 was the factory drill size for a 4 port. You will need a #50 drill to get .070. Make sure you drill at correct angle. I also have the tac-47 autoplug and love it.

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I am assuming you are having problems with some ammo. Check to see if any of your 4 ports are blocked before you drill the gas window larger. Also check the port size before drilling. I read from a previous post that .070 was the factory drill size for a 4 port. You will need a #50 drill to get .070. Make sure you drill at correct angle. I also have the tac-47 autoplug and love it.

Gas window was blocked so i will oversize after checking gas hole size and angle, after adding the auto plug and some cleanup on the bolt/carrier things should be looking up.

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so is this mainly for fwd and aft ports or does it count for left to right as well?

 

drilled at #50 all 4 ports and oversized gas hole to 11/32 still waiting on other parts to finish my build.

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hahahhahhah you said gas hole. but ya, i had to grind out the hole in the GB to let the gas flow...the rh side was halfway blocked. grind it away now it worky good!

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Folow up:

took her out to the range today, was quite excited to test her out with all 4 ports showing and expecting a great run. NOPE, didn't happen. matter of fact it was much worse!

Would not feed the same ammo that she was feeding when shoulder firing prior to this mod.

Decided it was time to figue out what the @#%@# was going on.

my proceedures to diagnose:

1) check bolt travel when firing: found it was only half of normal stroke. WHY?

2) checked ejection by hand: seemed normal, but stiff. Took time to grease all contact points including bolt locking lugs, bolt rails, bolt and carrier bore, contact area of hammer. (new gun)

3) checked ejection by hand again, felt smoother so I test fired: shell caught on barrel shroud. (some improvement)

4) Removed extended bolt-on charging handle (to reduce bolt mass and reduce gas needed to accellerate bolt), tested: every 2nd round FTE

5) Removed gas plug and piston: checked for fouling of any kind, none found. ran gas plug in until seated and only 10 degrees trun to lock into setting 2 (factory plug)

6) loaded one round, removed magazine and test fired: ejected case about 3 feet from gun. Although ejection was complete it should have done so with more distance (I think). Obviously there is a lot of friction between bolt and next round. just seem to be short on gas.

7) Removed foregrip and inspected gas block for signs of leakage: only indication was from gas vent hole.

8) removed gas plug and piston and inspected op rod alignment in gas tube: seem to be slightly off center.( Closer to barrel in gas tube) I'm being very critical of alignment when I say slightly.

Began to wonder if gas block was not truly aligned even though gas block pins matched barrel grooves well. Using plastic hammer and 8 ounce hammer I installed gas plug until seated, placed plastic hammer against plug and set the 8 ounce in motion..I noticed the slight misalignment seem to disapear after removal of the gas plug.

I put her back together, loaded one round and removed the magazine.......ejected the case about 9 feet from gun. shot the next round with mag in and ejection was complete with the case landing about 8 feet from the gun.

The next 150 rounds went off with no FTE's and all cases landing 7-8 feet from gun with a large upward arch.....SWEET

 

Summary:

I think the issue was: the gas block was slighlty mismatched (even though the retaining pins went in ok) causing some binding of the piston and/or op rod in the gas tube!!

 

THIS is what led me to the fix on my FTE's. Same as above, everything was right, holes unobstructed. The gas piston was slightly off center and catching the side of the gas block. My fix was fairly direct. I whacked the gas block hard with a rubber mallet. Amazingly it adjusted just enought to center the piston in the hole. Shot several mags (of high power ball) without a FTE after that. Ammo that would not eject before.

 

Thanks Nits!

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Great job on the post JeffD the information and photos are a great help and I thank you this will help me along with my own s-12

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still have fte's with cheap walmart ammo I can fire slugs and 3" no problem (of course) what Next? I'm running a 4 holer drilled to #50 oversized gas block to 11/32 tapco puck and an auto plug, gun is converted with ground g2 trigger and some bolt polishing. Anybody?

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Shoot good ammo for a few hundred more rounds! Have fun. If it still won't eat cheap crap, either buy good ammo or work on it some more.

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Here's a short video I made to help some of you guys out with questions about polishing parts. This is my first video so I apologize if it's a bit weak.

 

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sattv4u, did you try nitukamots suggestion about the piston possibly binding? I did the same modifications as you ( except polishing) and was then able to fire cheap federal loads. Did you mess much with the autoplug. If I recall I had to turn the screw in about 2-3 turns from the factory sent position.

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sattv4u, what are you using to retain your pins? If you are using a plate style retainer, I have seen some rub up against the bottom of the bolt carrier. The evidence will be in a mark across the bottom of the bolt carrier. If you perform the test in the video, does your bolt drop out? If not, inspect, inspect, and inspect again until you identify the friction points.

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My bolt drops out like the test above, I have profiled the trigger group and bolt etc. I have replaced the front spring with a css spring..I think the problem is the hammer spring is to tight so I'm going to go with a jte hammer spring. When I shoot low brass some do not push the hammer back to refire so I have a loaded shel but no trigger...(and yes I have done the gas work)

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Hopefully this thread still gets views and someone can answer my question(s). I purchased my s12 a few years ago. After converting it I havent done a whole lot with it.

 

I picked up saiga in 223 in Nov which brought me back to my s12 and I found this thread. When I check my gas ports, I have 3 of them but they appear to be smaller than 3/32. I tried removing the pins last night but Im not sure I am doing it from the correct side.

 

The directions say to lay the gun with the ejector side up, which I equate the right hand side of the gun (safety side, charging handle, ect). The pins are flush on this side and look a bit fat. When I flip the gun over on to the left side (side with the mounting bracket for the accessory rail) I notice that the pins dont come all the way through, they seem to be recessed in these holes. It looks to me like the pins were driven in from the right side and need to be pushed out from the left. Is this correct?

 

Sorry I dont have pics, since I am at work.

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I'm having trouble getting my gas regulator pin back in. I can put the spring in without a problem but the pin for the regulator seems to hit something before it can go all the way in. Any ideas of what I'm doing wrong or an do to get it to go back in?

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Great write up. Thanks to this forum for all the info. My Saiga would not cylce low brass, etc. I tried the MD V-plug and puck and still no luck. I noticed one of the gas ports was partially block by the block. Removed the block which was rather easy and filed away, also drilled the three ports to 3/32" why I was there. Polished the bolt carrier and hammer with my demmel. Took it to test today and it eats everything thru the stock and Surefire Mag. The Promag I have sucks!! Thanks again for this write up for the DIY peeps!!

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