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How much gap can the two sections of the S12 bolt have? Mine is running about .013" and allows the bolt face to rock to the point I can get a .020" feeler gauge in.

 

This gap also allows the bolt to cant upwards and hit the guide fingers of the barrel in combination with the play of the bolt in the carrier, bringing things to a halt before battery. When it stops, the extractor is about about 1/4" away from riding up onto the barrel. I've already filed/stoned the edges of both the bolt and guide fingers, and it has helped, but keeping the bolt straight would prevent the contact alltogether.

 

I'm thinking about driving the pin and adding shimstock to tighten things up.

 

This hangup happens reguardless of shell power.

 

So far my factory 4 port has cycled about 50% on Federal 2 3/4 dram "pink BC loads". That's the lowest I've tried. Of that box, only 2 mashed with not enough gas to hit the ejector, and the rest that didn't fully cycle either hit the ejector and stovepiped or had the above failure. I think when mine got drilled, they had a fresh bit and maybe reamed it a little.

 

Here's some pics of the guide fingers and the wear marks being made.

post-46782-0-78700900-1377229657_thumb.jpg

post-46782-0-13311400-1377229682_thumb.jpg

Edited by Capt Nemo
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  • 2 weeks later...

Just got back from testing.....I think I got it for the most part! Had 3 stoppages due to the bolt hanging up, and of those, one I caught myself riding the bolt. All were first rounds. The rest of the stoppages were Universal low gas problems. Federal bulk ran perfect. So my last polish/reprofile session did the trick.

 

Would still like to know how much play in the bolt sections is proper.

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Before I started reprofiling on the bolt and fingers, they'd overlap a good 1/64" which would really bring things to a halt. Now all it is is the pressure from the magazine on that first round that is able to still make things go goofy, so a little bit more stonework and it'll be perfect.

 

Also fixed the binding problem on my factory plug. The plug wasn't ground fully at the factory and still had threads where it should have been smooth. It would bind as #1 would come through the detent area. I took a Dremel sanding disk to the area where the threads should have been removed and took a few thousandths off. Threads perfect now. This might also be the reason that 2 3/4" slugs can't cycle and stop as they're extracting on setting #1.

 

The last thing will be drilling out the bottom pin and porting. I'm hesitant to do this, as I don't want to get off center on the pin and drill a hole in my barrel!

 

Dirt,

 

Looks like ~.020" is normal. I guess it's just the combination of tolerances that's messing with mine. Looks like you have a pretty good knick on the rim of the bolt face. That area is what I had to round over to get things sliding. Mine didn't have a knick there, but there were some coarse file marks there.

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Took it out yesterday and ran an almost flawless 200 rnds of Federal bulk. Had a total of 4 failures to lock up, of which 3 were first rounds, and one during cycling. Had 2 undergas failures in the last 10 rounds. At 160 the gas block was smoking pretty good! On cleaning, I couldn't move the puck as it was so gunked up with carbonized plastic. Took a helluva lot of brushing with a stainless brush, and pick scraping to clean it out of the gas block. All the brushing also took the finish off the top of the barrel by the gas block. Also noticed that some of the Federal bulk loads had a bulge just above the brass. Some of the bulges looked wider than the brass and might have led to the chambering issues.

 

Overall, had a GREAT day! Tried the rubber band bump fire trick, and could get a few 2-3 rnd bursts with it, but I could fire it semi just as fast and more accurate. No problems hip firing. And the forest of zombie nettle didn't stand a chance. Also took my father along (89 and a WWII vet), and although too frail to shoot anymore, had a ball watching the dammage my Saiga could do!

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attachicon.gifDSCN0432.JPGMine looks like that too.

I think it likes to be that way because the last 500+ rounds thru it were flawless. All Federal 7 1/2 value packs.

attachicon.gifDSCN0410.JPG

That is called the barrel hood, not fingers.

 

And, you need the tollerance between the bolt head and the bolt body.

 

It is not a precision instrument when it comes to the timing between the carrier/interface and the bolt/lug interface during the locking and unlocking of the bolt lugs and that is why there is what appears to be an excessive play between the body and the head of the bolt.

 

You can start messing with areas that will destroy the reliability of the gun if you do not have the basic gun knowledge or experience.

 

There are not very many people out there or on this forum who understand the exact relationship between the parts during a complete cycle and when the bolt locks into battery and when it unlocks from battery. What appears are slopy tolerances are necessary for these parts to perform properly.

 

Jack

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Agreed. I can imagine problems if the bolt was any tighter.

Capt Nemo, it looks to me like your barrel is in good shape, nice and smoothed up from the parts working together. Might want to leave that area alone.

Also, I think a bit of resistance right before things go into battery is normal.

You don't want to be too gentle chambering that first round.

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I've been reprofiling the leading edges so the bolt will slide and not come to a dead stop. Before reprofiling the bolt could hit squarely 1/64" up the guides/hood and hang up.

 

This is the malfunction I was having.

post-46782-0-91286600-1378394424_thumb.jpg

 

After some work.

post-46782-0-29612200-1378392782_thumb.jpg

 

Rounding over the edges and polishing the rubbing surfaces on the bolt, and angling the edges of the guides/hood has reduced this problem. Right now, I've almost got it licked, where I only saw it once during cycling and 3 times during manual charging on a full mag. It's due to both the slop of the carrier/bolt stem and the two pieces of the bolt riding up over the next shell in the magazine, which can hit and jam up the works. Any reduction in the carrier/bolt slop would also help prevent this.

Edited by Capt Nemo
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Have fun, but that is not the problem.

 

Nobody can truly diagnose the problem over the internet, but it may be as simple as the initial timing roll over is not correct between the barrel hood and the bolt. This will cause the bolt to stop/bind since it won't be allowed to go into battery.

 

When the timing is correct, the bolt will go in and out of battery like it is on ball bearings!

 

Jack

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If you say it's not the problem, then why when you put upward pressure on the bolt simulating the pressure from the magazine, does it hit and grind on the hood? Also, the bolt is no where near being able to lock up as it's still needs to travel 1/4" to lock in it's slots. The bolt is still resting on the trunion part of the rails. With no upward pressure, the only thing impeading lock up is the extractor overide on the barrel.

 

I just had another thought, my trunion may not be properly aligned with the reciever. That would bring the barrel hood down, and cause the bolt to go high. It would also explain the rubbing on the carrier by the trunion.

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EVERY Saiga Bolt will ride up and hit the barrel hood if you put upward pressure on it. Also, there is nothing wrong with relieving the contact area between the bolt and the TOP of the Barrel.

 

What you do is put a light bevel/radius, just enough to break the square edge, on the inside/top edge of the barrel.

 

You NEVER modify the Bolt Face of any weapon system, unless you have the equipment to perfectly square/true the bolt face, such as truing up a bolt action receiver and bolt.

 

I guess a Saiga is as good a platform as any to learn on, so keep at it!

 

I will try and get a picture of the bolts relationship to the barrel hood and the initial bolt roll over I am talking about. I know I have already posted pics and information about this a couple years ago, but I don't know where it is at.

 

Jack Travers

JT Engineering

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The only mods to the bolt face I've done are rounding over the edges. The edge came from the factory with coarse file marks. I've rounded the area so it can't hit the barrel with a flat face.

 

Here's the bolt as it is now.

post-46782-0-74262100-1378421463_thumb.jpg

 

As you can see, I'm not really taking that much off the bolt face, just enough so that it doesn't hit square. You can see a little damage from the last firing session up by the extractor. That's around 1/64" into the bolt face. A little touch up with the Arkansas stone should clean it up. A rifle bolt face is much more critical due to the pressures involved. But at 12K in a shotgun, a little off the side to get things sliding won't hurt.

 

As for timing corrections, the gun has been doing that on it's own! I've had to file/stone down peened areas in the timing channel, and smooth down one side. Here's the damage on the bolt.

post-46782-0-29107600-1378422877_thumb.jpg

 

There's one little peened spot on the top of the lug that needs stoning down, as it will drag on the floor of the channel pretty soon. And you can also see some deformation at the front as well.

 

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Congratulations, you may have destroyed your bolt if you took materiel off that lug!! That deformation at the front of the lug is where the lug on the bolt body has been hitting the barrel hood as it started to go into battery!! A little bit of a burr is not uncommon.

 

That is the MOST critical angle and determines when the bolt will start to rotate into battery and then the carrier channel will rotate it the rest of the way into battery.

 

If you notice the angle that is on the right side/top of the barrel hood, that has a direct relationship to that lug you stoned/messed with. I have enclosed a pic where you may be able to see what I am refering to.

 

Look at the angle on the barrel hood and the angle of the lug on the bolt body as they almost come into contact. The lug I am refering to is the one behind the extractor.

 

When the bolt is traveling forward, that lug will contact the angle of the barrel hood and start it rotating into battery.

 

Jack

post-11998-0-98209500-1378427514.jpg

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Be sure that what you're seeing is not the hood being too tight. I had one come through here that was .020 undersize. You couldn't get it to close with a shell in the chamber. Thats probably the oddest one I've seen yet.

Like was said, the bolt will ride the hood when you put upward pressure on it. Some good info was given

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I'm sorry, but that lug does not hit the barrel hood to start the locking process! It is the cam channel of the bolt carrier that that lug resides in, and it is the forward motion of the carrier that causes the locking process.

 

The forward deformation on that lug was caused by the rate at which the carrier was thrust backwards. The front of my carrier channel has also been hammered about .040" deeper. The material that mushroomed out of the channel had to be filed off as it rubbed on the bolt. This kind of damage would be from overgassing. The rear tang on the carrier is also mushroomed from impacting the hammer, and there are marks from rear trunion impact. I have run around 250 2 3/4" magnum rounds through this gun on factory plug setting #2. #1 would not even get these rounds to extract more than about an inch. On #2 they were so strong that I cracked the pistol grip from the recoil.

 

But anyhow, the gun is now cycling better than it ever has! Before I started working on her, she wouldn't even cycle a 3 dram target load. Now, I can cycle 2 3/4 dram about 50% of the time and the factory ports are still intact. At 3 dram, the only problem is the hood hangups on the first round, and once in awhile during cycling. It's a lot better than the 2 - 4 per magazine that I was having.

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+1 Jack. When are people on this forum ever going to stop trying to argue with guys like yourself, Matt, Tony, Will and the rest who have forgotten more about working on guns than most will ever learn? Guys who (before ever even seeing their first simple Saiga) were building complete guns, even machine guns from scratch, occasionally give enough of a damn about people here to try and share a little knowledge, and then end up having to argue with the very members they are trying to help. Sometimes I've given up on trying to help folks for months over one argumentative thread with some misinformed member (or several piled up) who refuses to listen to my experience and advice because they just think I want their money. I've also seen many other knowledgable folks throw their hands up and just say fuck it for the same reason.

 

Secondly and every bit as imporant is this. I've been adamantly posting about this for years now. There are several if not MANY whole threads full of extremely bad (if not literally dangerous) information and "how to tips" posted on this forum...the very same forum people all over the world look to for good information on these weapons. Every day people read some of the garbage written here and even STICKIED in some places. That shit needs to be removed from here because I see posts about parts (and actual parts coming in for service) that have been completely ruined by folks following what they are misled into thinking is good advice. Something really should be done about it because the longer some of that shit stays up, the more thousands of people read it and accept it as gospel here.

 

People seriously need to watch what they post on here about firearms modifications. Many people don't realize just how much BS has been written and accepted as gospel here with these mods, gas system mods, FCG mods, etc....and they don't all know to take internet advice with a grain of salt here. This forum has grown into an information library and does get used for reference. The bad info should all be weeded out somehow and stricken from the records. People are using it to ruin perfectly good guns and may even hurt themselves or others by following some "how to" post here. I know one thing, I sure wouldn't want to be the one responsible for that happening. I would MUCH rather be thought of as "stengy or secretive" and withholding tips and info, than someone misreading or misunderstanding something I meant as good advice, then end up with problems.

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For the sake of anyone who is interested, I am going to explain exactly how the Bolt "Timing" works and why it is so important that the angles of the barrel hood and the top lug of the bolt body not be improperly modified, filed, ground, profiled, etc.

 

I have put the picture of the bolt and the receiver in this post so you can see the relationship of the two angles I am referring to. The angle of the Barrel Hood and the Angle of the lug on the top of the bolt body. This is the same lug that you fit the bolt into the carrier/slot when you are reassembling the two components.

 

Imagine taking the barrel completely out of the receiver, now there is just a hole through the front trunnion. Now set the carrier/bolt assembly onto the rails in the proper position and push it forward like it was stripping a shell from the magazine and then going into battery.

 

This is what it would do: The bolt will keep going straight with NO rotation until it stops against the front trunnion of the receiver. Why? Because it take the angle of the barrel hood and the top lug of the bolt body to come into contact with each other, STOP the bolt from going any further forward and to START the clockwise rotation of the bolt body. THEN the carrier will continue to move forward (bolt is stopped) and complete the roll over of the lugs into complete lock up/battery.

 

The angle of the barrel hood is so critical because it indexes the bolt exactly where it needs to engage the male lugs with the female lugs. Move the angle a few thousands forward the the front edges of the bolt lugs will beat themselves trying to go into the female lugs because they will try to engage a few thousands too far forward.

 

This is the "TIMING" that I refer to. I like to have it within +/- .002 not to beat the lugs.

 

NEVER take advice from someone who does not even know the name of the components of the weapon system and then that person talks in 1/64s instead of decimals as in thousands, ie: .002

 

There is too much bullshit being put out on this forum and no one is calling the people on it.

 

I also posted this under a separate topic.

 

Jack

post-11998-0-71075200-1378485276.jpg

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I have two receivers here with the barrel removed. I put the bolt/carriers in them and slid them forward. The bolt won't rotate unless I help them by providing some initial bolt head rotation, and then the dog-leg in carrier takes over to fully lock it.

 

Jack is correct.

 

However, I am not convinced anything in this thread is causing that problem. I would take a look at the face of the feed foot on the bolt.

 

Tony

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i think the problem is the canuter valve is broke along with it needing brake light fluid. that doomaflitchy can be tricky so i recommend bubble gum, duct tape and chicken wire. now if i could just figure out if my headlights need halogen or fluorescent fluid i would be set.

 

its a ak type thingy, all i really need is a hammer, punch and chisel!!!!

 

big_smile.gif

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Tony's right!

 

The stripper claw on the bottom is part of this problem! This problem does become more apparent with certain magazines. I record what magazine I have in the gun when a failure occurs as a way to detect a potentially bad magazine. So far, AGP mag #3 is the worst of the 10 I have for this failure. The stripper is digging into the next round, pushing the bolt into the hood, and lifts the right locking lug off the rail and into the trunnion. I have angled the trunion slot a little to allow passage and force the lug/bolt back down without a braking impact. The lug would hit just after the bolt would hit the hood. So now, everything that the bolt can hit up top has been taken care of.

 

Here you can see the result of the stripper claw catching on the shells. Looks like it catches the next shell in the magazine at the payload cup and halts.

post-46782-0-24838400-1378841413_thumb.jpg

 

I generally see this failure in the first 5 rounds out of the mag. I'm also seeing this in the factory mags as well, so I believe it's more of a gun problem than a magazine problem. The mags don't want to back the next round down for the stripper to pass, and it rides the shell hard and can catch. On rounds that cycle OK, there's just a worn streak in the side.

 

The stripper claw rides pretty low when stripping, and is almost not needed, but it is also needed for ejection, and therefore is critical. I'm going to try rounding the side that rides the shell hard, but keep the inside part as intact as possible. Looks like it's going to be a long "file/test fire/repeat" operation to smooth this one out.

 

 

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I am trying to figure out if we should just can this thread all together… I am afraid that some unsuspecting new user or a lurker would not read all the way through it and start touching it up, filing, re-profilling, and/or rounding… :(

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I agree on trashing it. I'm not afraid to tinker on firearms but I'm by no means a gunsmith and can see the potential for a lot of new people screwing up their guns because of this. I started on this forum when people like Tromix, JT, Cobra and others were sharing their knowledge and now its a bit of a free for all. They all have forgotten more information on the saiga platform in a good nights sleep than most of us will ever know.

Edited by Skitterfish
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