My AK blew up

[TargetTerror]

I took my first hand loads for my AK to the range last night. Suffice it to say, things didn't go as planned. I am fine, fortunately, though my ego has been hit down a notch or two. I fired about 5 rounds with no problem. POI was way off, but the rounds fired and cycled fine. They actually felt much lighter than the cheap Wolf ammo I normally feed my AK. On about the 6th round, the gun fired and the explosion seemed much closer in (though not appreciably more intense), the top cover blew off and some hot gas spurted out the top. The bolt was stuck, and took a few good whacks to pull the case head out. The rest of the cartridge remains in the chamber. Ironically, this shot had the best POI of any of the rounds I loaded

I loaded some old lead bullets I that I got on sale in brand new Winchester brass on top of 14.5 grains 2400, with Winchester LR primers. The lead bullets were sized to .311, were 150 grains, had gas checks, and other than having lube all over them, seemed decent enough. COL was ~ 2.060", give or take a bit.

The gun still seems to function and cycle fine, though I obviously haven't tried another round yet. I think the bolt is FUBARed. The firing pin flops around, which I'm pretty sure it didn't do before. The extractor also looks slightly bent, and there is a gap between it and the rest of the bolt face (red arrows in the pics). The top cover is bent, and I'll need a new one of those too.

It looks to me like the round fired out of battery. If you like at the picture of the case head with the red arrow, the arrow is pointing to a band just beyond the groove of the head. That looks to me like the cartridge was unsupported there. What do you guys think?

I have 2 theories about how that could have happened. I first thought that some of the excess lube got in the the chamber, and prevented the round from chambering fully. That did seem a little odd for only 5 rounds, plus the 5 I shot didn't have a lot of lube up on the bullet itself. My other theory is that the the bullet wasn't seated in far enough, such that the bullet actually hit the lands, preventing the round from seating fully. If you like at the photo of the rounds, the lead round is definitely thicker up at the top then the FMJ. I didn't want to seat the bullet much deeper for fear of raising the pressure. ~2" COL was what the manuals seemed to say for this bullet weight and type.

Anyone know a good place to get a new bolt and top cover? This is a Romanian, WASR, if that makes any difference. Also, it looks like I will need a broken case extractor. Who makes a good extractor for 7.62x39, and where is a good place to buy it? Does this look like something that I should have a gunsmith look at before shooting again? The barrel/chamber area seem ok. It just looks like the bolt that took the beating. (One question on the chamber: are the 2 cuts in the chamber face - the red arrows in my pic - supposed to be there like that?)

I was lucky I wasn't hurt, but this is a reminder to be careful!

(I can't upload photos for some reason, but I posted this on another forum too. The photos can be viewed here: http://www.thehighroad.org/showthread.php?p=4242094#post4242094)

 

[Admin]

I'm glad you're okay.

 

[TargetTerror]

I'm glad you're okay.

Thanks, me too!

 

[doobie]

I seem to hear so many reloading issues like this with people blowing up their guns.... I'm glad I started reloading already.... cuz I'd be scared sh*tless to start now.

One thing I have found is...either my scale is way off, but the starting loads seem to fill my case. I always used slightly lower. My accuracy did improve, I went up about 5-10% on the AQT. I think half my problem is rushing through.

Also I ordered the RCBS scale/dispenser so hopefully that'll be nice. I ordered it since I needed a new dispenser cuz at the moment I haven't a clue where mine is (some box somewhere that I'll find the day the RCBS arrives).

 

[LoginName]

Damn... that sucks!

At least you walked away from it with two good eyes and all 10 fingers.

I can't really tell from the pics if the bolt and chamber are okay or not. They appear fine, but I'd have to pull the bolt from one of my AKs to compare with the pics, but I don't have access to my guns at the moment.

K-Var http://www.k-var.com/shop/home.php?cat=271 has bolts, top covers and broken shell extractors.

I have a couple of spare top covers if you want one (PM me your address). They should fit with a little fudging around (almost all top cover fitment is like that anyways).

The K-Var bolts are Bulgarian and may not be correct for a WASR (they're not cheap either).

Even if you do find a correct, inexpensive bolt, you could end up with a head spacing problem.

I'd advise asking some of the AK gurus at http://www.akforum.net, http://www.akfiles.com/forums or http://www.ak47.net for answers/remedies.


Pics hosted for those without a THR account...

 

[Twigg]

I'm glad you're okay.

+1, Sounds like you had an angel sittin' on your shoulder.

 

[z0mbi]

I seem to hear so many reloading issues like this with people blowing up their guns.... I'm glad I started reloading already.... cuz I'd be scared sh*tless to start now.

[sad2]

 

[1903Collector]

Geez, thank god for small miracles. Glad you are O.K. could it have been a slam fire before the bolt locked up? High primer perhaps. I use the CCI arsenal primers now on everything I load for my ARs or M1A..

 

[wilfx]

Ask the people at www.GUNCO.net Theres alot of AK expertise there.

 

[TargetTerror]

Thanks for all the advice and thoughts, much appreciated. I registered at those sites you listed, LoginName, now I just have to wait for the admins there to activate my account.

The slam fire theory is interesting. I was using WLR primers, which are definitely softer than CCIs and military primers. I'm quite sure none of the primers were high. The Dillon priming system on the 550 is good, and I'd have felt if something was amiss while priming.

Also, can an AK even slam fire? I poked around on the 'net, and it looks like it has a free floating firing pin. Would there be enough momentum simply from the bolt flying forward to igntie a primer, even with a non-sticky firing pin? the pin moves freely now, though it did have a major incident so its current state might not be the way it was beforehand.

 

[Finalygotabeltfed]

Some questions.

Is the case that is in the chamber fully seated against its shoulder in the chamber?

Is there excessive leading in the barrel near the chamber throat?

Did you inspect your brass before reloading it?

Does your charge fill the case or is there ample room for a double charge?

I see that there is alot of brass flow into the bolt face. This is caused by high pressure(and from experience, I'd bet this was the cause here), not an out of battery detonation. An out of battery detonation would not have left the rear of the casing intact as it is....it would look like a cartoon cigar....like a daisy.

I'd be checking my powder weights, the integrity of my brass and the fit of the bullet in the throat of my barrel. I'd also be looking into the need of a gas checked bullet or be using FMJ.

 

[Cuda444]

First let me start by saying I'm glad you're ok!

Second, I'm not sure about the AK, but on an AR, if you instert a mag and send the bolt home, then eject the chambered round, you can see a slight dimple on the primer from the free float firing pin, even on mil-spec ammo. I've read of a few (not many) cases of the primer actually igniting when this happens. Has it happened to me? No. But hearing the stories and seeing the dimple is enough to make me take extra care when chambering a round... It could happen. YMMV

 

[Finalygotabeltfed]

First let me start by saying I'm glad you're ok!

Second, I'm not sure about the AK, but on an AR, if you instert a mag and send the bolt home, then eject the chambered round, you can see a slight dimple on the primer from the free float firing pin, even on mil-spec ammo. I've read of a few (not many) cases of the primer actually igniting when this happens. Has it happened to me? No. But hearing the stories and seeing the dimple is enough to make me take extra care when chambering a round... It could happen. YMMV

From firsthand experience, I assure you the pictured damage was due to over pressure, not a "slam fire" from a floating firing pin nor was it an out of battery detonation.

An out of battery detonation would have disfigured the forward edge of the casing where it separated from the front half. The picture clearly shows a clean edge at the point of separation. This is indicative of a defect in the brass(most common in reloaded brass) and the brass flow into the bolt face/ deformed primer and the rupture in the sidewall near the web is indicative of extremely high pressure.

A slam fire (on a properly loaded cartridge with good brass) that properly chambered, would not have done anything but fired just like any other round.....and hopefully in a safe, down range direction.

 

[Jose]

+1 on the signs of overpressure.

 

[LoginName]

That looks like a pretty solid primer strike to me. Too solid to be a slam fire.

Regardless, if your bolt isn't FUBAR'ed, disassemble it and give a good cleaning to remove any traces of cosmoline in the firing pin channel.

Did you save the brass from the rounds that fired safely?

If so, check those for any signs/indications of over pressure.

 

[Adam_MA]

Another vote for over pressure!

Glad you didn't get hurt, and as far as your gun goes... Put it back together and shoot it again.. It's an AK!

 

[THUNDERCHIEF]

Well, at least you didn't loose any fingers ....or worse.

 

[1903Collector]

A slam fire (on a properly loaded cartridge with good brass) that properly chambered, would not have done anything but fired just like any other round.....and hopefully in a safe, down range direction.

Not to get off track, but what would happen if the round did go off before the bolt locked up? Could it even happen?

 

[MFP4073]

I noticed the flat point bullets.

Maybe its possible that when the bolt stripped a round of the mag it didnt feed right and it jammed the bullet on the edge of the chamber / breach face and pushed it into the case causing the high pressure.

Perhaps you can make up a few dummy rounds with no powder or primer and chamber a few without the dust cover on to see how they go in. If the bullets push in you know you got a problem.

Anyone?

 

[BLAM]

Whitey I was thinking the same thing! If that flat nose bullet caught an edge coming out of the mag or going into the chamber and got pushed into the case that would most certainly cause an over pressure failure! If you have a light crimp that could contibute to bullet movement in the case in these service rifles as well.

 

[Finalygotabeltfed]

Not to get off track, but what would happen if the round did go off before the bolt locked up? Could it even happen?

Yes it could happen. If the cartridge seats into the chamber but the bolt doesn't lock up it can cause a casehead separation but there isn't the kind of brass flow or case damage that is pictured or it can just fire and extract and eject without incident.

Much depends on the strength of the casing, whether brass or steel and its less likely to separate if its new brass and not a reload that has previously been stretched and or weakened from a previous firing.
If the cartridge doesn't seat all the way into the chamber, it usually blows the case apart into a ragged edged front and back halves, sometimes the rear portion looks like a daisy.

The picture shows a clean casehead separation with a smoothe edge all the way around the circumference of the casing, but there was a pressure failure behind it and the case head has flowed into the contours of the bolt face and extractor. This means the cartridge was fully seated but had an extreme pressure spike that didn't dissipate even after the bullet passed the gas port at the front of the barrel. The pressure vented through the side of the casing and the primer.

 

[TargetTerror]

I talked to a local gunsmith, and I'm going to have him check it out and make sure everything is ok.

There are a couple of facts that I may have implied but not stated outright that should affect some of the analyses I'm seeing. First, this was literally the 6th or 7th handload that I fired out of this gun, ever. Everything else had been Wolf FMJ. As such, I seriously doubt leading of any part of the chamber or barrel was to blame. I buy the arguments that lead will shave off somewhat in the chamber and off the gasport, but that should only happen after many many rounds. I've read too many reports of people shooting lead in AKs and SKSs without problems to believe that 6 rounds would cause such a catastrophic failure. I don't know the exact hardness of these bullets, but since they had gaschecks, they were clearly designed for higher velocities.

I also don't buy the slamfire argument, because the gun did not slamfire. I chambered the round, slowly took aim, and then pulled the trigger. The round went off when I pulled the trigger, not when the bolt closed. There was probably at least 5-8 seconds in between closing the bolt and pulling the trigger. A slam fire should occur immediately, correct?

I also checked and yes, I could fit a double charge of 2400 in the case. But, that would have been a VERY compressed load, which I'd hope I'd have felt. The powder was may 1/3 or so of an inch away from the top with the double charge. Also, the bang when this round fired didn't see all that excessive - it just seemed like it came from the rear of the barrel instead of the front. I don't have any other experiences with such failures, but I'd think a severely overpressured round would sound VERY loud.

Thanks again, and keep the opinions coming, I'm curious!

 

[RKG]

1. Bearing in mind that any long distance, sight unseen diagnosis is more or less speculation:

2. I tend to concur with those who see an overpressure case separation.

3. If you discount an excessive charge, here is another possible hypothesis, which in part takes as its departure the unusual shape and diameter of the slugs used:

4. What is supposed to happen when you fire a bottleneck cartridge is as follows:

a) Case expands slightly in the shoulder and neck region, enough to release the bullet, which jumps forward to the rifling.

b) Obturation is not sufficient at this point to prevent the case from sliding aft in the chamber so as to bear up firmly on the bolt face.

c) After its rearward movement has been arrested by the bolt face, case obturates to the point of making a good gas seal at the neck. Balance of the case expands to fill the chamber, which provides the support without which the case cannot contain the peak pressure.

5. Two things here could have caused the failure I believe occurred. One is that, because of the diameter of the slug, the outside diameter of the neck of the case was over spec. This wedged the case hard enough into the forward region of headspace that the neck case neck and shoulder were not able to slide aft. When the rest of the case slid aft, the side wall forward of the head and web was stretched and separated. The other is that the chamber is oversize, and when the case expanded to fill the oversize chamber, it thinned the wall forward of the web and it separated. Possibly both factors were at work.

6. In addition to any other tests performed, I would (a) have the chamber cast and measured and (b) take one of the loaded rounds from the bench and mike the neck diameter.

7. I repeat that diagnoses such as this are not worth much.

 

[1903Collector]

Yes it could happen. If the cartridge seats into the chamber but the bolt doesn't lock up it can cause a casehead separation but there isn't the kind of brass flow or case damage that is pictured or it can just fire and extract and eject without incident.

Much depends on the strength of the casing, whether brass or steel and its less likely to separate if its new brass and not a reload that has previously been stretched and or weakened from a previous firing.
If the cartridge doesn't seat all the way into the chamber, it usually blows the case apart into a ragged edged front and back halves, sometimes the rear portion looks like a daisy.

The picture shows a clean casehead separation with a smoothe edge all the way around the circumference of the casing, but there was a pressure failure behind it and the case head has flowed into the contours of the bolt face and extractor. This means the cartridge was fully seated but had an extreme pressure spike that didn't dissipate even after the bullet passed the gas port at the front of the barrel. The pressure vented through the side of the casing and the primer.

Thanks for the info