i have read the entire thred atleast once since the magwell is the receiver and the bolt is in the receiver, out of curiosity how do you know?

i thought the OP might say more about it. i know he said they were cut up and sold without taking pics.

Hence the saying... "stamped receivers last a lifetime, milled last 3 lifetimes"

Are you using rate reducers in your WASR conversions?

I have read in several places that without the rate reducer, stamped AKM receivers can set up excessive vibration in F/A fire which may exhibit rail wear.

Well obviously I wasn't there so I can't say that I know. However, I've built/repaired more than enough of them to have an idea. They posted this picture showing where they would weld the receiver in anticipation of a crack forming:



So given that's the area of failure, let's look at the options. First, the single stack bolt. What makes a single stack bolt different from a double stack? Well, the lower extrusion of the bolt that contacts the rounds in the magazine is lower than it's double stack counterpart. All other parts of the bolt are the same dimensions, to include the bolt lugs, which are the only real parts that continually contact the receiver. So if the failures aren't being observed in other double stack bolt, 1mm receiver guns, then it's safe to conclude it's not the contributing factor.

Left is single stack, right is double stack:


Second, is the magwell. At the point where the weld is made is at the point just before the magwell get's "thicker" as it transitions into where the beak of the mag is inserted. This area, though, is typically the same or more thick than a WASR, which also has its magwell opened up by Century. As has already been stated by Henderson, the WASR has been their golden child. So if the failure isn't observed on the WASR which has the same proceedure and overall dimensions of the NPAP, then it's safe to conclude that it's not the issue.

Top is NPAP, bottom is WASR:



What could be the problem? In an AKM/earlier pattern AK, the bolt carrier contacts the right side of the trunnion when it reaches its forward most travel. Since the right side contact point of the trunnion is located well within an area where the receiver is solid, the forces being generated on the trunnion as a whole are causing more stress on the left side of the trunnion where the receiver is cut for the magwell. Now, as we stated previously, if this failure point isn't observed in the WASR which follows the same principle, why is the Yugo failing? Could it be that the reports of Yugo rifles not being properly heat treated are the cause? Possibly. I wouldn't make that claim without testing one, but at this point it would seem plausible.

Point where bolt carrier contacts front trunnion and its approximate location in relation to the receiver (same for WASR and NPAP):

Great write up. I cant believe no one has done a hardness test to compair the recievers yet?

Most AKs I've seen the bolt carrier rarely contacts the trunnion on the right side, but instead on the left on the large shoulder of the locking lug. The AK-74 even has an angular surface here versus flat surface on AK/AKM - not sure what the purpose is but someone revised the contact surface.

I'm in China right now so I can't look but I recall my M92 having an indent in the receiver in the location of Henderson's crack. It's possible that Zastava is doing something weird when bending the receiver into shape, as the indent looks like what you typically find on rails and such as indication of where they were pressed in a sheet metal bender.

All AK's prior to the AK-74 should have the bolt carrier contacting the right side of the front trunnion as this is how it was designed. There should be a gap between the bolt carrier and the left side of the front trunnion. This was changed with the AK-74 to contact the left side and, as you stated, they added the angular contact point. Every example of pre-74 AK that I have contacts on the right and every post-74 AK contacts on the left.

No one wants to sacrifice their rifles to prove the existence of a problem that may have potentially been limited to a few batches (or possibly even a single batch) of receivers.

i appreciate the detail pics ans knowledge

i am not as versed in these items, but i feel i can now understand my own question better. i am slowly reading through the thred about this thred on the AK files in hopes of someone dropping some more knowledge. i am also trying to reads the yugo/ robski thred on the files, but it gots drama.

ost

don't see a general firearm thread anywhere so i'll ask this here:

1. what exactly is happening to the uzi top covers that deadlines them and how often?  I've only got one spare and if I need to buy more i'd rather do it while they're somewhat plentiful and cheap

2.  tell me everything you know about BARs.  I'm lusting after one but whether I get one or not has a lot to do with parts availability and reliability

Here is a Century M74 Sporter that was first put on the line back on 10 NOV 12. This rifle has an extensive cleaning list with zero parts replacement. The headspace has remained within spec after all this time and it's a US-made barrel. I don't know who Century subcontracted these out to but it certainly served it's purpose until it started keyholing.

That target looks bayonetted.

Chrome lined barrel?

About how many rounds before it started keyholing?

No.

I've haven't had a chance to review all the maintenance records on that rifle but considering the day it was put into service, a VERY conservative number would be no less than 50,000 rounds.

V/R
Ron

More than likely we will but not anytime soon. The receiver still looks perfect so I will have to purchase a new 5.45 bolt along with the barrel when the time comes.

V/R
Ron

What are the issues you've experienced with the RPDs? I've built a couple posties(sadly now sold) but never put more than 10k rounds through one. Very curious if they were rewelds or commercial receivers.

Way off topic, but did those weapon lockers have stickers that looked like this on the interior of the door??

We have used both rewelds and Vector/DSA receivers on the line. One thing they all do is start to crack at the rear half of the receiver near the take-down pin. All of the receivers fail in the exact same manner and wouldn't say one is better/worse than the other. I can't remember which parts specifically but I know that we've had a couple top covers go down from parts coming loose.

On the last two DSA receivers that went on the line, we actually welded some saddle plates over the take-down holes and and made longer take-down pins. They haven't suffered from any cracks as of yet and they've been on the range since early February IIRC.

A little tip for you guys that own either a post sample or semi-auto RPD. If you didn't receive one of the tobacco-style blued cleaning kits, purchase one. Your weapon shouldn't have a problem running on the first gas setting and it will help extend the life of the receiver by not beating it up. If the weapon starts malfunctioning, most people will want to increase the gas flow and put the setting on the second or third setting. After extended use, the gas ports on both the barrel and the gas cylinder will foul up. The cleaning kits come with a port scraping tool that fits perfectly into both the barrel and the gas cylinder and unlike a drill bit, screwdriver or other sharp object, you're not going to remove any material and speed up the erosion process. It also has a wrench that is the correct metric size to remove the gas setting plug without any chance of stripping it because it grabs it on all corners.

V/R
Ron

Yes, they have that sticker. I sent my staff down to San Diego to pick them up after purchasing them from a government auction.

V/R
Ron

Thank you. Should be easy to take care of if I want to build another some day. One of the ones I sold went to a range in Vegas. Can't remember the name, think they went out of business though.

Very cool, great info in this thread. I think I got the other lot of them in Barstow. Most of the inserts were still intact..

I thought it was San Diego but you are correct, it was Barstow. We purchased two lots of them and I want to say we paid under $75 each? Did your rubber inserts smell like old rotten fish? We had to soak them in a bleach solution, let them dry in the sun for a couple of days and repeat that a few times until they were odor-free.

V/R
Ron

Can you tell me more about the Draco-Cs? You mentioned that you're down to one. Were the round counts to failure on them similar to WASRs, etc? Do they have more or less issues than other AK variants?

So, if I have read this thread correctly, what I have learned is:

Milled receivers out last stamp.
Stamped receivers will suffer cracked trunion at 80,000-100,000 rounds
Bolts will last to about 80,000 rounds.
The gas tube will erode in 100,000+ rounds
US barrels (74's) will last for around 50,000 rounds.
Simple Green is safe to use for cleaning.
AK's last longer then RPD's
WASR is bad ass!!

Right?

Remember reading that the AKs made by those Pakistan "gunshop towns" are crap and aren't properly heat treated. Specifically remember someone mentioning that the metal used for the bolt carrier was soft enough to gouge with a steel nail. It's hearsay so take it as that, but considering that the Vice media video about one of these towns shows customers "test firing" weapons on the rooftops to "make sure they don't explode", I wouldn't doubt it.

Pretty good summary

I will have some more pics of a bolt that suffered some major erosion and the weapon was only on the line for slightly under three months. The hot gas eroded a hole clean through the stem of the bolt.

V/R
Ron

Here's an example of one WASR that didn't last as long as others. This is not the norm but with all of our past good experiences with WASR's, this is definitely worth noting.

A little background on this exact WASR. It went on the line 09 JUN 15 and has been used every day since with the exception for routine weekly cleaning. It was never off the line for a whole day, just cleaned and put back in service. This WASR did see quite a bit of use because of the new blonde furniture and RSO's usually grab the cleanest and "prettiest" weapons as previously discussed. The weapon did NOT have any function or reliability issues, it was just brought for cleaning when all of these issues were identified. The first thing that my armorer noticed was the erosion in the bolt. After seeing that, they figured there had to be other issues so they took their time and checked further for other issues. That's when they noticed the erosion through the gas tube and the crack in the rear trunion. Again, this weapon continued to function properly but it had to be pulled at that point because of safety issues.

As for round count, AK's, Uzi's and AR15's get the most use but because of the "double your ammo" special with the AK, they get run even more. I can say a fair estimate for this weapon is 30 times in a day with magazines loaded to 25 rounds. If you take that number and consider it was on the line for 3 months, then a fair round count is 60,000+ plus rounds during that time period. Before anybody starts knocking the quality of the WASR's, this is the first time we've seen such wear on a fairly low-round (in our experience) WASR to date. The headspace is still within spec and there are no signs of wear or fatigue on the bolt or trunion. The rounds are still hitting the center of the target accurately (at 10-15 yards) and not keyholing.

V/R
Ron

I take it you find it easier to rock in a magazine that's downloaded?  Or more reliable feeding?  Or the magazine springs last longer?  Any other mags you find downloading helpful in?

Or 5 rounds saved X every mag X every gun = saved $$$

We load 25 rounds to make things easier on our accounting. The ammo comes packed in 1,000 round cases and it's easier to "GI proof" the loading and accounting situation with an easy number of 25. We know that we can get 40 loaded magazines out of a case of ammo with zero extra rounds floating around in comparison to 33.3 magazines loaded with 30 rounds per magazine.

V/R
Ron

This AK was put on the line less than two months ago. The date was 11 OCT 15 to be exact and we already suffered a cracked rail. This is very unusual for any of the WASR-series of AK's to experience this kind of failure at such a low round count. This is a good example of things that are way out of the norm but when it happens some people online will right away say "my WASR only lasted 15,000 rounds and it cracked.. it's a POS". I know from our experience that isn't the case but every products made is going to have a sample that for one reason or another fails. We will be able to weld that rail back in place and hopefully that's the end of issues but we will definitely keep an eye on the other rail during each cleaning to inspect for any stress cracks that are forming.

Ah - "tactical accounting".    That makes a tremendous amount of sense.

Any word on the C39's with headspace issues? Did pressing the barrels further in and re-pinning them fix the problem?

wow,awesome thread!!thank you!!this makes me want to go out and buy a wasr!!

Bump

It did fix the problem and if you know how fractional an amount of distance is involved in headspace, it worked. An over-size barrel pin was used (after the original hole was opened up a slightly).

BTW, just to clarify which milled rifle had the headspace issue. I didn't go back re-read my posts but I believe I called it a C39 thinking that all of Century's milled AK's were C39's. This particular rifle was one the very first Polish Model 1960 rifles to be sold. I know there is a difference between the Polish 1960 in comparison to the C39 that was my fault if I called it a C39.

V/R
Ron

Lost me here. You said you had 3 C39's from the initial batch that had the non-chrome barrels. Is this gun referenced above a different gun than one of those three C39s?

Any experience with the Yugos with thicker 1.5mm receivers like the M70ab2?  I always wondered if those are really stronger than the standard stamped 1mm receivers.

Ron,
Thanks for the clarification, glad it worked out.

Anything new?

I'm sure we're all dying out here waiting on more pics and data from you guys. Love the failure pictures.

Thank you for a great thread!

The only thing that we've seen recently that was out of the ordinary (from our regular experiences) is a gas tube that had a huge hole blown through the side of it. The weapon continued to run properly and nobody complained of hot gas bothering their hands or fingers and was only discovered after it was disassembled for cleaning.

I believe we at least 30+ AK's that are all off the line due to cracked stamped receivers or barrels that keyhole. We will probably just deadline those AK's into dummy guns at this point. We have dummy'ed several of them with welded up chambers, welded over firing pin holes, firing pins removed and the magazine follower welded to the body. There is no way they can chamber a round or even pick up a round at this point.

V/R
Ron

Would they not be worth more being cut up and sold off for parts?

OR they could decommission 30+ AK's (I'm sure they could break more to add to the pile), slap on matching style furniture (for uniformity's sake), and make a foyer/hallway that is literally just lined with AK's along both sides like you're walking through an armory. Put them in military-style racks at eye level and put some spotlighting on them. They seem to do 75% of things just for the sake of being badass, so this doesn't seem to be out of the realm of possibility

OP/Ron, great thread and thanks for sharing all the information! A lot of people are concerned about the bolt carrier and bolt on the C39V2 and RAS47 (which has the same). How have these held up long term for you guys (how many rounds)? I know you mentioned a C39 earlier in the thread, was this a V1 or V2?

No C39's, it was a Polish 1960 done by Century that had headspace issues. One rifle, at least I think that's what he meant. He'll chime in soon enough.

I wish we could get this clarified. Yes he had C39's. The rifle you were speaking about he did call it a C39 too, but then said it wasn't.

Here's his quote from this same thread many moons ago:

Hey Ron,

I'm sorry if you've already stated this and I have searched but what brand of ammo and flavor do you run in the 7.62 AKs? I'm assuming you guys run the type with the least amount of issues.

Thanks again!