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3rd lug Saiga vs PSL Bolt.


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I know i've read here on several occasions that it would be unadvisable to modify the lugs on the .308 bolt, from a practical and safety standpoint, and I agree, but I never really understood why the saiga has a third lug, nor have I, as I sadly dont own a saiga .308, ever seen how the .308 bolt differs from the standard akm bolt.

 

I understand that the theory is that the .308 generates significantly more force than the 7.62x39 and thus requires more lockup to ensure its safe operation under those pressures, but there must be something I am missing.

 

The PSL fires the 7.62x54 round which can be loaded to nearly identical pressure as the standard 7.62 nato round, and the psl not only has but two lugs, the lugs are of the same profile as the standard AK47 bolt, and thats not to bring up the .308 PSL, which was of limited import. Ive been told (but again, never seen) that the .308 saiga has beefier lugs to begin with, in addition to the third lug. Is there a reason that the beefer lugs werent enough, and the third lug was added? Also making me wonder is the .308 galils, which have a standard two lug bolt as well, and the Zastava m76, which fires the only slightly lower pressure 7.92x57mm round. Is the change a result of revised testing standards, that didnt effect the old guns, are the other guns somehow unsafe, or is there some other variable, pressure curves or material concerns, that I might be missing here? Arent there other examples of AK's in .308, does the VEPR have a third lug? What about the Valmet or the Zastava M77? I dont have any experience with those, so i could be wrong, but i think they are all two lug designs as well, are they just that much beefier of lugs?

 

Is there any chance that someone here might feel generous, and could upload a couple of pictures of exactly how it is setup?

 

And dont worry, as I said, I dont have a Saiga .308 and im not about to blow myself up by hacking at one (and dont recomend anyone else does either), Im just currious about the technical aspect and wondered if anyone had any opinions.

Edited by ReverendFranz
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Well, yeah, but that doesn't answer any of my questions about the saiga's unique bolt, though the article you linked to do show that there was a change in testing in 2006. They lowered the standards.

 

Its irrelevant as the saiga, afaik, hasn't changed in those years, and the CIP standard (Russia being a CIP member state) was lowered, from 130% to 125%, meaning that all of the older guns that I mentioned, as well as the earlier saiga's had to be held to a Higher standard.

 

Also, the proof requirement is in Russia, not the US, the US has no proofing requirements, and is entirely voluntary.

Edited by ReverendFranz
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Hahaha, well fuck em. Like i said, im not grinding on one, I dont even have one to grind on if i wanted to, I have no reason to grind on one, im just wondering about it from a design standpoint, and a general interest in firearms technology. Id like to see either measurements or pictures so i can see exactly what they changed, and if the two original lugs were beefed up as well, or not, and hear some theories about what the potential reasonings might have been.

 

Thats all, not planning on blowing myself up, anytime soon anyways.

 

Someone has to have a camera or a set of calipers, right? Help a brother out?

Edited by ReverendFranz
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I agree with the pics!! Most high power are 2 lug systems. My old Ruger M77 only had 2 lugs on it in both the .270 Win and the .338 Win Mag configuration. Only thing I can think of is the a beefier setup from the 7.62 x 39, and this was one way to improve on it. The Russians are very frugal, and would not put extra metal and time into machining just for the sake of marketing.

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The only information I have ever come across about the number of lugs on the .308 Saiga's bolt was over on Valery Shilin's site. It states near the top of his Saiga .308 webpage ( http://izhevsk.club.guns.ru/eng/sig308.htm ) that:

 

The bolt is adapted for a larger size of ammunition. The new construction of the bolt, with three locking lugs to replace a two-lug design of the original AK-47 assault rifle, enhances the accuracy factor.

 

So it would seem making the bolt on the Saiga .308 a three lug bolt instead of a two lug bolt was done mainly for (if not only for) the purposes of increasing the accuracy of the rifle, not because it was necessary to deal with the larger and higher pressure .308 cartridge. Now I have no idea how increasing the number of lugs would increase the accuracy, but like I said this is the only information I have ever been able to find about the design reasoning behind the .308 Saiga's three lug bolt.

Edited by Frogfoot
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look how many freaking lugs an AR bolt has. They can be very accurate.

 

Okay, but why does having more lugs on its bolt make the AR-15 more accurate? Also, what about all the precision shooting bolt action rifles floating around? Those are very accurate and they usually only have two lugs.

Edited by Frogfoot
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look how many freaking lugs an AR bolt has. They can be very accurate.

 

Okay, but why does having more lugs on its bolt make the AR-15 more accurate? Also, what about all the precision shooting bolt action rifles floating around? Those are very accurate and they usually only have two lugs.

 

I agree, Shaq has alot of shoes, but that doesnt mean that if you have alot of shoes, you are ready to go into the NBA.

 

In this case, i think that the lug does contribute greatly to accuracy, and is why a stamped sheetmetal gun from russia is capable of some pretty tight groups, even when compared to more expensive stiffer guns, like the milled galil, but that doesn't have anything to do with the AR, which we all know has 7 lugs, because Stoner wasnt able to figure out how to turn a bolt more than 15 degrees of rotation, anymore than he could figure out how to make a rifle without directing all of the fowling into the most critical and sensitive areas. ;)

 

I dont know if thats the reason the third bolt was added, but I am pretty sure that was the effect of it. Which, of course, is why I asked if anyone could take a picture of a bolt, to see if the original two lugs were beefed up or not. (I guess everones .308 bolts are at the cleaners.)

 

The reason the third lug would effect accuracy is positional repeatability, think about it like vertical stringing on a rifle, try shooting a rife one handed with the forend in a vertical slot, and then again resting in the bottom of a "U" shape. As the bolt cams closed, the third lug is going to push the bolt up, into roughly the same position (or closer) every time. the closer everything is to the same position, the more repeatable the shot, and the smaller the group. The reasson the two lug bolt guns work well without doing this is that they dont have the vertical play that the ak has because of the larger tollerances it uses to obtain its exceptional reliability. The question is, if accuracy is the only reason, why arent all the saiga bolts 3 lug?

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Franz, I see the issue about accuracy and the AR. I don't think it was an accuracy issues as much as it was an issue to rotate the bolt as little as possible to lock in battery. I don't support the idea of increased accuracy with an additional bolt for this reason. ALL of the major match grade rifles would have 3 or more bolts if that was true, but, they don't. Match M1A Garands have 2 lugs. Even match grade target rifles have 2 lugs, with the exception for a few of some of the rifle manufactures that used their own proprietary designs. When a round goes into battery it is held in place by he bolt-face/extractor. Headspace is at issue, and given that the chamber is correct and the headspace is correct, the actual bullet would be held in place and headspaced off the shoulder to the face of the bolt, as in this case the actual bolt face. On the .223 this is not so, as the first contact area is the raised rim area round the primer that determines the headspace. Goofy idea!!

 

This link in the .308 forum here gives some pictures of a bolt head with the 3 lugs. It's about 3 pages back now: http://forum.saiga-12.com/index.php?showto...34785&st=30 Some of the pictures in this thread are kind of fuzzy, but there are a few decent pictures. Perhaps this will help.

 

 

I don't have one to look at and pose this question. Does that 3rd lug actually engage any major part of the receiver for holding in the round, or is it there for some other reason? You know, they may have just put it on there to add to the length that the bolt carries uses to push down on the rounds in the magazine. You see, as the bolt cycles that part of the bolt carrier that has a ramp to it pushes down the rounds AND also starts the hammer back to engage the sear. It could very well be that there might have been issues with the round not being fully pushed down when the hammer was cocked and canted the top round a bit and made it difficult for the bolt to grab reliably and take into the chamber. Is this making sense to you what I am implying? That extra lug may have nothing to do with the lock up but may have everything to do with feed reliability from round to round.

 

Then I may be all wet.. LOL Sounds like a politician huh? Explain how it should work and then disqualify himself as not knowing anything. Really, without looking at one in my hand I am just speculating about this idea.

 

Here is another link to a picture of a gouged .308 case...very badly gouged! http://forum.saiga-12.com/index.php?showtopic=31277 It was posted just last Novemeber, but has shown that if that 3rd lug is not done right, what can happen. I don't think he can reload that round, even with a lot of bondo.

Edited by Darth AkSarBen
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post-3-0-56655200-1307622045_thumb.jpg post-3-0-47563500-1307622046_thumb.jpg

 

post-3-0-49263700-1307622042_thumb.jpg post-3-0-27611200-1307622044_thumb.jpg

 

Awesome, thats exactly what i was looking for, thanks Darth.

 

You might be right about it keeping the magazine feeding clearly, i hadnt thought of that, though, like you, I dont have one to look at, From what I understand, though, the third lug does lock into the trunnion. Looking at those pics, you can clearly see that the two standard lugs are beefier than a standard x39 bolt, which should be more than enough to take care of the pressure, unless there is another concern. The PSL bolt, and the Galil bolt, if im not mistaken, i cant find the picture, have the same bolt profile and lug size as a standard x39 AKM, and the M76s in .308, imported by zastava is also a two lug design, though one of the lugs is enlarged to take the pressure. Im pretty sure the VEPR has a similar bolt, and the Here is that bolt, next to a yugo bolt from a m70 x39.

 

post-3-0-44971300-1307622048_thumb.jpg

 

It looks to me like the Saiga bolt has BOTH lugs enlarged, and should be very capable of handling the pressure.

 

SN: yeah, i remember that thread, but it seemed to have been slaughtered by the legal and prophet departments, between the disclaimers and the 72 point font predictions that you were going to die, it didnt seem to get very far, thats why i thought it best to start a new thread, without any plans to cut on a s308, to see if i could get more technical information. For example, i dont think anyone answered your question about peak and dwell time. I think its definitely an interesting design change.

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Hold the peak of your index finger over the muzzle and fire the rifle. Quickly remove your finger. If you don't have a finger to remove, you let it dwell too long, hence a peak dwell. An Obama in a deck of cards is one joker too many. That's a peak as well...or some word that starts with "P" and does end in "K" :haha:

 

I am sure what SN is after is the fact that the .223 round is fired and exits so fast out of the muzzle that there is less time dwelling in the barrel at any peak pressures. Heavier, larger bullets, traveling slower down the barrel will have a longer time where they are at their peak pressures before the pressure start to dwindle. This is all done in milliseconds, but to steel, they are an eternity. Something in a 22" barrel also has to be considered as there is a longer time of holding (peak) the pressure in the barrel before exiting. Hence, the 16" .308 probably will need a bit larger hole for the port for gas to work the piston VS the 22" barrel that now has to constrict down the gasses escaping somehow before the bullet leaves the barrel, else you would have a lot of that peak pressure trying to go down the recoil tube and have a pretty hard recoil ejection.

Edited by Darth AkSarBen
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  • 3 weeks later...

I think I understand why the AR type bolt contributes to its accuracy. The seven lugs makes the bolt only need to rotate 45 degrees to unlock. That's far less a motion comparing to a two-lug bolt...not to mention that the weight of the bolt + carrier, the gas blow back, blahblah.

 

What I am curious about is the side by side comparison of the SIG bolt vs the AK bolt vs the XCR bolt vs ..., you name it. :rolleyes: That should be very interesting.

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  • 1 year later...

I never really understood why the saiga has a third lug...Im just currious about the technical aspect and wondered if anyone had any opinions.

 

I have a Saiga .308 and the 3rd lug is a design error. Other 308 AKs, like the Galil and the Valmet 76 and 78, work fine with the traditional 2-lug Kalashnikov design. All the third lug does is to beat up the next round waiting in the mag, and make it very hard during assembly to push the bolt carrier down into the receiver. It is some Russian "Bubba's" guerrilla engineering. Kalashnikov would never have done it this way.

To try to make it work the way Bubba intended you are fighting against 2 irreconcilable contradictions.

(1) The 3rd lug needs to be rounded enough to pass over the next round in the mag, but also

(2) square enough to provide a tiny couple of mm² lockup interface with the trunnion.

It's all crap. I just ground my bolt down so the right side looks like the left (looking at the bottom side with the head up).

It works fine of course. Doesn't explode, no gouging, bolt slides over the rounds in the mag real smooth, bolt just drops into receiver during reassembly. Locks up and generally works the way Kalashnikov intended. Locks up like a Galil 308 and a Valmet 308. Bubba needs to be sent to Siberia.

 

I don't want to hear from people afraid to pull down a totem pole put up by somone they assume must have known what they were doing. Just remember the US military would not accept the Thompson Submachine gun until Thompson removed the useless "slipping inclined planes" blowback delaying mechanism. Google it!

post-31036-0-36008300-1302894578_thumb.jpg

post-31036-0-74283900-1302894662_thumb.jpg

Edited by gnugung
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I ground down my 3rd lug to a point I felt was entirely safe and shaped it for maximum contact during lockup and minimal drag over shells in the magazine.

 

 

Used a diamond jewelers file to get the shape then a dremel to polish it out. Runs like any fine piece of engineering now.

If you don't know what you're doing, don't remove metal. Better yet, if you have to get information like this from a forum and you don't already know what to do, don't do it.

 

If it causes malfunctions and any damage to a brass case while hand cycling it, it needs to be taken care of to be 100%. I feel that a bolt that has the ability to cut a hole in a casing is far more dangerous than one that might not lock up good enough to launch bullets that should never be used in a 1:12 twist barrel. Stay under 150gr regardless, it's entirely pointless to go heavy with that slow of a twist.

 

When 180+ is recommended for a 1:9 twist or faster, I don't see why anyone would use them in a 1:12. Especially out of a 16" barrel.

Edited by Tombs
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  • 2 weeks later...

I had to modify mine. The 3rd lug interfered so much that you could not pull the bolt back further than 1.5" or so, when the lug made major contact with the round on the left side of the magazine, if that one was on top (odd numbers). When firing, It would stop completely anytime the round on the left side was on top. So a very small amount of filing was done, and it works like a charm. A little marking of the cases still occurs, but it is no longer a single-shot rifle.

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The bottom "third" locking lug on the bolt of my first Saiga 308-1 was too large. It was almost impossible to cycle a round into battery. The third locking lug even ripped open cartridges with powder spilling out inside the gun. I posted some pictures on this forum on another thread a year or two ago. I sent the Saiga 308-1 back to Scottsburg, Indiana and they ground the third lug down so it would function properly. Even though it's just a little nub of metal I think I'll leave it alone. Better safe than sorry....but it is kind of strange nobody has a valid answer as to just why it is there.

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  • 2 weeks later...

It's there to provide additional lock up strength.

 

The question isn't why it's there, it's if it's necessary. A lot of people tend to think it's necessary and a lot of people don't.

 

Nobody is willing to be blamed for someone modifying a gun and having it blow their hand off or worse.

 

 

My 2¢ is that it should be there, but you need to make it profiled and shaped well enough that it doesn't negatively affect feeding or cycling. After what I did with mine it runs like a charm and I have no fears of running any kind of ammunition in it. After altering the shape and height of mine, it has a ton of contact with the trunnion and I believe it actually will make some kind of difference.

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  • 2 weeks later...

material concerns

 

Well, looks like you seem to have a pretty good grasp on the situation, answered your own question with a question, gratz.

 

Do you know what kind of materials each of those various countries used to construct their rifles? Not just the bolt but the trunion also? And how that type of metal was annealed and tempered?

 

No?

 

Ok, then any further speculation is useless.

 

Keep in mind that quite a few British Enfields were modified to chamber 7.62 nato, which will also chamber 308 which has been shown to be beyond the safe limits of (not the design but) the material from which the rifles were constructed. The Indian 308s are built visibly similar but with stronger steel.

 

P.S. You'll put your eye out kid.

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If that part fails, it doesn't blow your hand up, it sends the bolt carrier through your right eye and into your brain and you die.

 

However cutting off that lug will make your rifle cycle 15% faster, which is deffinitely worth the risk.

 

OR better yet, mod it and sell it at a gun show without telling anyone what you did.

 

:osama:

 

Seriously guys? talk about some bubba smithing...WECSOG is one thing, but this is redickalass

 

I'll be sure to only buy factory new saigas from here on out, or visibly inspecting the internals before pulling the lever. No telling what you might run into these days. :rolleyes:

 

(Just when I think you couldn't do anything dumber, you go and do something like this, and TOTALLY redeme yourself!)- Dumb and Dumber

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I just ground my bolt down

 

how many rounds downrange? 100? 500? what happens when it gets to 5000 rounds? ever hear of metal fatigue?

 

You won't own that gun forever, some day you will die and some innocent person will be putting round #000 downrange, ormaby they get some bad ammo with over preasure issues like that indian 308 from a few years back....Please don't ever sell that gun. and before you die, please destroy the bolt and throw it away, before some innocent person dies.

Edited by santanatwo
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If that part fails, it doesn't blow your hand up, it sends the bolt carrier through your right eye and into your brain and you die.

 

However cutting off that lug will make your rifle cycle 15% faster, which is deffinitely worth the risk.

 

OR better yet, mod it and sell it at a gun show without telling anyone what you did.

 

:osama:

 

Seriously guys? talk about some bubba smithing...WECSOG is one thing, but this is redickalass

 

I'll be sure to only buy factory new saigas from here on out, or visibly inspecting the internals before pulling the lever. No telling what you might run into these days. :rolleyes:

 

(Just when I think you couldn't do anything dumber, you go and do something like this, and TOTALLY redeme yourself!)- Dumb and Dumber

 

How fast does an AK bolt & bolt carrier move? 600 rounds per minute? So that's 10 cycles per second? How far must the bolt carrier move to extract? 3"+ at least. So for argument's sake (Since i have no S-308 in front of me) let's say that in 1/10th of a second the bolt moves 3" to the rear and then 3" back forward. (Please view:

) Notice how it takes about half as long for the bolt to move to the rear as it does to move back forward. 1/30th of a second to move 3" back, 2/30ths of a second to come back forward. 4/30ths of a second to move 1'. Seven and a half feet in a second. 7.5FPS.

 

 

Please view these catastrophic AK events, and note than no one lost a head.

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During Vietnam, the USA special forces had a program where they planted overpressure 7.62x39 ammo in magazines and ammo boxes, just one round in a case, or in the middle of a mag, and when the round went off, it sheared off the trunion/bolt lugs, and the carrier went through the right eye of the NVA soldier.

 

facts, how do they work?

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