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FTE after enlarging gas holes... twice.


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I thought I had overcome undergassing, and have posted a few time thinking I was good to go... but here we go again. I have a restored s12, lightweight hammer spring, gogun puck, gunfixer plug, Tromix FCG/DIY triggerguard. I have broken in w/200+ high brass heavy loads, polished everything, have 3 holes which I have enlarged twice (now at 7/64) and STILL do not get 100% ejection rates (Federal bulk pack). Don't get me wrong 1 out of 50 is way, way better than before, but not good enough in my opinion to consider this gun race ready. I have had it choke up big time in last 2 multi gun matches, after I assumed it was fixed by shooting 49 of 50 rounds without failure.

 

My question is, although I feel I have made good progress, what else would a person do to improve reliability. I am considering:

 

1. Adding a choke

2. Bead blasting the bolt

3. Re -intalling original puck back (no reasoning to that other than read it somewhere here)

4. Shoot high brass for match (do I go to setting "2" now that I opened up the ports?)

 

 

any further suggestions?

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I really don't know how all the hole measurements work out.. but I just kept drillng one size up until it worked, or taking the drill that fit the current size and just drilling the sides of the holes a bit.. Or check and make sure your FSB sits so it doesn't obscure the holes.. You may be running on 2 or even 1 hole without knowing it thanks to them being placed in a spot thats covered by the FSB, and if that's the case I'd drill a new hole in a better location.

 

Also make sure the holes you built are slanted apropriately like / with a bit more angle (assuming the front of the gun is to the left)

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I really don't know how all the hole measurements work out.. but I just kept drillng one size up until it worked, or taking the drill that fit the current size and just drilling the sides of the holes a bit.. Or check and make sure your FSB sits so it doesn't obscure the holes.. You may be running on 2 or even 1 hole without knowing it thanks to them being placed in a spot thats covered by the FSB, and if that's the case I'd drill a new hole in a better location.

 

Also make sure the holes you built are slanted apropriately like / with a bit more angle (assuming the front of the gun is to the left)

 

All holes are clear with no obstruction, proper angle, ect. I am concerned about going 1 size larger for 2 reasons: First, I think it will run into the adjacent hole and fubar the whole thing, and second, I am getting 1 FTE per 50 rounds, with the rest running well. Like I said thats pretty good, but really, to expect a gun to jam once every 50 rounds is pretty sketchy. I don't feel comfortable using at a match with those odds. I already have a bad habit of checking ejection every round that I am trying to break, so thinking at least 1 round per stage will jam just sucks. I need just a breath more I think.

 

I had another idea to throw by you guys. What if I made the gunfixer setting 3 cavity a little bigger?

 

As for the lightweight recoil spring, I used that prior to 2nd gas hole enlargement. Replaced w/old spring because I had to shoot slugs periodically throughout a stage - I may put that back in and go "reduced" recoil slugs - they shoot about 1,200fps right?

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I thought I had overcome undergassing, and have posted a few time thinking I was good to go... but here we go again. I have a restored s12, lightweight hammer spring, gogun puck, gunfixer plug, Tromix FCG/DIY triggerguard. I have broken in w/200+ high brass heavy loads, polished everything, have 3 holes which I have enlarged twice (now at 7/64) and STILL do not get 100% ejection rates (Federal bulk pack). Don't get me wrong 1 out of 50 is way, way better than before, but not good enough in my opinion to consider this gun race ready. I have had it choke up big time in last 2 multi gun matches, after I assumed it was fixed by shooting 49 of 50 rounds without failure.

 

My question is, although I feel I have made good progress, what else would a person do to improve reliability. I am considering:

 

1. Adding a choke

2. Bead blasting the bolt

3. Re -intalling original puck back (no reasoning to that other than read it somewhere here)

4. Shoot high brass for match (do I go to setting "2" now that I opened up the ports?)

 

 

any further suggestions?

 

From what I've highlighted, have you been running low brass loads and trying to get them to run 100% on setting #1?

 

The gas plug is designed to allow enough gas to cycle the action using high brass (heavy) loads on setting #1, setting #2 allows more gas into the system and is for lower brass light loads. I suspect if you try the Federal Bulk Pack on setting #2 it will probably work great now that you have over enlarged the ports to .109. It may even be over gassed now.

 

Just my .02 I hope you are able to get it up and running for your shooting matches.

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I thought I had overcome undergassing, and have posted a few time thinking I was good to go... but here we go again. I have a restored s12, lightweight hammer spring, gogun puck, gunfixer plug, Tromix FCG/DIY triggerguard. I have broken in w/200+ high brass heavy loads, polished everything, have 3 holes which I have enlarged twice (now at 7/64) and STILL do not get 100% ejection rates (Federal bulk pack). Don't get me wrong 1 out of 50 is way, way better than before, but not good enough in my opinion to consider this gun race ready. I have had it choke up big time in last 2 multi gun matches, after I assumed it was fixed by shooting 49 of 50 rounds without failure.

 

My question is, although I feel I have made good progress, what else would a person do to improve reliability. I am considering:

 

1. Adding a choke

2. Bead blasting the bolt

3. Re -intalling original puck back (no reasoning to that other than read it somewhere here)

4. Shoot high brass for match (do I go to setting "2" now that I opened up the ports?)

 

 

any further suggestions?

 

Try it on setting #2. Setting one virtually cuts off gas relying mostly on recoil from the shell to drive the bolt back. Setting #2 puts gas in front of the puck to push the piston back.

 

 

Let me back up a little here.... are you using a "fixer plug"? If you are try the factory plug on setting two. Also the factory puck works just fine.

 

WS

Edited by WaffenSchmied
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Some other ideas...

 

Are you using an action buffer? If so remove it and see if that cures the problem.

 

Is the bolt carrier leaving a mark on the back of the reciever like it is slamming into it?

 

Are the bottom of the rails rough?

 

Do you have any pin working it's way out of the bolt/ca

 

If you try all of the above, it could still be under gasses. I would not go bigger on the hole size... I would add a fourth if there's enough room. Some factory models come with four holes.

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check the profile of your new hammer against the original factory hammer while you are at it.

 

Good point Ben. That extra resistance can make a world of difference. Along with honing and polishing the rails, and rail channels on the bolt carrier, I reprofile the hammer faces on all of my conversions. It makes a huge difference!

 

You don't need any more hammer face sticking up than is necessary for the disconnector to engage, and the hammer face should be as close to parallel as possible to the bottom of the bolt carrier, with a smooth transition angle on the front and back of the hammer face.

 

WS

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check the profile of your new hammer against the original factory hammer while you are at it.

I actually started with the tapco FCG, and thought that the profile was too high, thus slowing

the bolt. I therefore replaced with the Tromix FCG, as I understood it was the correct size.

I will check that again.

 

I did replace the gogun puck with the factory puck and went to test, and fired for the first

time ever 50 consecutive rounds without FTE. My logic (with absolutely no scientific support) is

the gogun puck, with the groves in it, allowed more gas to fill the space prior to cycle, while the factory

puck does not allow more gas in since there are no groves. I am certain this is incorrect but

since it worked I am going to run with it.

 

Is it safe to say that the factory plug on setting 2 allows the same or more gas in as the

gunfxr plug on setting 3?

 

I am going to keep my fingers crossed and run with it for the match this weekend. Hopefully

the pumpgunners won't have something to laugh at anymore!

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Yes, the "Twister" pucks will bleed off some gas. Or call it "blow by", like a piston engine with bad rings.

The "Magnum" will bleed off the most gas, followed by the Medium, and then the Standard having the least gas leakage.

 

Not to say the Twisters are bad, just that they require more gas than the stock puck to operate.

 

Which one were you using?

 

 

Edit: Forgot they have a standard "Go-Gun" puck that is not a Twister, curious to know which one you have.

Edited by Spartacus
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Yes, the "Twister" pucks will bleed off some gas. Or call it "blow by", like a piston engine with bad rings.

The "Magnum" will bleed off the most gas, followed by the Medium, and then the Standard having the least gas leakage.

 

Not to say the Twisters are bad, just that they require more gas than the stock puck to operate.

 

Which one were you using?

 

 

Edit: Forgot they have a standard "Go-Gun" puck that is not a Twister, curious to know which one you have.

 

I have the twister standard:

http://store.carolinashooterssupply.com/servlet/-strse-309/Saiga-E-dsh-tac-Gas-Piston/Detail

 

 

Good to hear my theory is not all that off kilter. I went ahead and checked

out the profile on the Tromix FCG, and there is (was) quite a bit of

room to dremel and still get full function, so I did, front and rear,

and it appears to help hand cycling a little. I thought the Tromix

was designed to not have to do that, so once it was in I figured all

was well, because the tapco one was way high, and I ground the hell

out of it before I replaced it.

 

Thanks to all for the help, I really appreciate it.

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Update: 100% function at match today..Woohoo! Finally got to utilize the full potential of mag fed shotgun! Our multigun matches do not seperate limited and open, just assisted sighting and iron sights, so it is a HUGE advantage to hold 13 rounds and reload so fast. The old 'nelli is gonna be pretty lonely stayin home from now on!

 

Thanks again for everyones help, on this thread and my others....this site is an excellent resource and i would have given up long ago without it.

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I thought I had overcome undergassing, and have posted a few time thinking I was good to go... but here we go again. I have a restored s12, lightweight hammer spring, gogun puck, gunfixer plug, Tromix FCG/DIY triggerguard. I have broken in w/200+ high brass heavy loads, polished everything, have 3 holes which I have enlarged twice (now at 7/64) and STILL do not get 100% ejection rates (Federal bulk pack). Don't get me wrong 1 out of 50 is way, way better than before, but not good enough in my opinion to consider this gun race ready. I have had it choke up big time in last 2 multi gun matches, after I assumed it was fixed by shooting 49 of 50 rounds without failure.

 

My question is, although I feel I have made good progress, what else would a person do to improve reliability. I am considering:

 

1. Adding a choke

2. Bead blasting the bolt

3. Re -intalling original puck back (no reasoning to that other than read it somewhere here)

4. Shoot high brass for match (do I go to setting "2" now that I opened up the ports?)

 

>109 on the ports, how did I miss that???

.100 with three holes should be plenty. Actually, I'm thinking I wouldn't go beyond .96 for port size. Maybe add the fourth SMALL if I was sure it was nessassary.

 

any further suggestions?

 

From what I've highlighted, have you been running low brass loads and trying to get them to run 100% on setting #1?

 

The gas plug is designed to allow enough gas to cycle the action using high brass (heavy) loads on setting #1, setting #2 allows more gas into the system and is for lower brass light loads. I suspect if you try the Federal Bulk Pack on setting #2 it will probably work great now that you have over enlarged the ports to .109. It may even be over gassed now.

 

Just my .02 I hope you are able to get it up and running for your shooting matches.

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So what was it that got iy running?

 

Was it reprofiling the bolt?

Well, replacing the puck with the factory puck got me zero failures to eject for the first time

ever. I honestly believe that the groves in the gogun puck require just a hair more gas to

actually fill the cavity, and it appears that is all I needed.... but I must say, when shooting

those 50 round with no FTE, I must have been getting juuusst enough gas, because what happened

for the first time, is the bolt did not come FORWARD after ejection, and got hung up with a

failure to feed, however the round was in straight just waiting for the bolt to drop. My hypothisis,

once again with absolutly no supporting data, is that the gun had barely enough to properly

eject, and when it cleared the back hump of the trigger, was on its last breath and hung up. It

only took a touch to get it to go forward into battery. So, I

reprofiled the Tromix hammer, rounding the edges of the front and back of the hammer that touch

the bolt, and polished it up. Upon hand cycling it felt like there was much less resistance than

before, and boy o boy it ran like a champ in the match!

 

I was under the impression that the Tromix FCG did not need any reprofile, and as I explained

before I replaced the tapco one I had due to this consideration, and never considered reprofile of

the Tromix unit. I do not wish to dispute whether it is drop in or not, and I certainly hope that

additional modification to the part does not offend the maker, it just seemed to work for me.

 

In addition, the gogun puck is an awesome unit, and I mean no disrespect to the maker and am

in no way suggesting that it does not work. Apparently my gun was possessed and bound and

determined to make my life hell for a few months, punishing me for never testing to see if

it worked prior to conversion.

 

I would however pose a question to those qualified to comment: What if a puck was made that was

thicker, that essentially takes up more space in the gas block, thus reducing the required amount

of gas in the chamber to cycle? I contemplated putting a same size washer in there on top of the

puck (kinda like a brick in the toilet tank) and adding washers until it was good...any thoughts?

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If the puck is much thicker, probably varies a little from gun to gun, the bolt will push back out of battery. It may or may not still fire, but with the gas adjusting plug(Gun Fixer Plug looks longer) all the way in, or even less with the Gun Fixer plug, the extra space in the gas tube/block is very small. You might want to take a few measurements first.

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Im glad it worked out for you.

 

 

Others doing thier own conversions, should note how important reprofiling the hammer and even rounding it's facets corners a bit improves the bolt's cycling.

 

 

you may want to go run some heavy loads down the gun on gas setting one to finish breaking it in, and try the etac pucks again with your target loads. you are probably overgassed now.....

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So what was it that got iy running?

 

Was it reprofiling the bolt?

Well, replacing the puck with the factory puck got me zero failures to eject for the first time

ever. I honestly believe that the groves in the gogun puck require just a hair more gas to

actually fill the cavity, and it appears that is all I needed.... but I must say, when shooting

those 50 round with no FTE, I must have been getting juuusst enough gas, because what happened

for the first time, is the bolt did not come FORWARD after ejection, and got hung up with a

failure to feed, however the round was in straight just waiting for the bolt to drop. My hypothisis,

once again with absolutly no supporting data, is that the gun had barely enough to properly

eject, and when it cleared the back hump of the trigger, was on its last breath and hung up. It

only took a touch to get it to go forward into battery. So, I

reprofiled the Tromix hammer, rounding the edges of the front and back of the hammer that touch

the bolt, and polished it up. Upon hand cycling it felt like there was much less resistance than

before, and boy o boy it ran like a champ in the match!

 

I was under the impression that the Tromix FCG did not need any reprofile, and as I explained

before I replaced the tapco one I had due to this consideration, and never considered reprofile of

the Tromix unit. I do not wish to dispute whether it is drop in or not, and I certainly hope that

additional modification to the part does not offend the maker, it just seemed to work for me.

 

In addition, the gogun puck is an awesome unit, and I mean no disrespect to the maker and am

in no way suggesting that it does not work. Apparently my gun was possessed and bound and

determined to make my life hell for a few months, punishing me for never testing to see if

it worked prior to conversion.

 

I would however pose a question to those qualified to comment: What if a puck was made that was

thicker, that essentially takes up more space in the gas block, thus reducing the required amount

of gas in the chamber to cycle? I contemplated putting a same size washer in there on top of the

puck (kinda like a brick in the toilet tank) and adding washers until it was good...any thoughts?

 

My personal experience is that the factory puck -- the one engineered for the gun is the right one. I think aftermarket pucks are fine for compliance parts, but don't believe they offer any performance advantage, and in cases where a puck may be partially rifled, necessary energy that would normally be used to push the puck straight back is instead converted to torque.

 

You were correct in reprofiling the Tapco hammer to allow the bolt carrier to move over it without excess resistance and you are right that at this point, Tromix does not reprofile the hammer face on the Tapco G2 FCG's to work better with S12's, although I wish they would.

 

As for making the puck larger, I think that may work against performance as adequate space for the expansion of hot gas in the block is necessary to accelerate the piston back with sufficient force to move the bolt carrier.

 

I build a fair number of these guns, and it sounds like yours is responding to the thoughtful, and well reasoned work you are doing. Getting an S12 to perform consistently under demanding conditions is a balancing act, and you are on the right track.

 

WS

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look at the saiga12's factory hammer. that is the profile you have to match.

 

 

With that said, the gun is probably overgassed now, and I would recommend steering clear of 3" loads without some sort of countermeasures, or you will risk bending the op rod......

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