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PKM Parts Layout

7K views 35 replies 6 participants last post by  kingofbeer 
#1 ·
Note that the measurements for the trunion I got are 1.614" wide, which happens to be 41mm.

I'm not sure if I am missing some parts or if I have spare parts. I've managed to figure out the assembly for everything except the few parts I've identified. So if anyone can help with the one pic I'd appreciate it!

This has tons of pics (about 60) so beware if you're on a slow connection...

http://pookieweb.dyndns.org:61129/beltfeed/PKM/pkm.htm
 
#2 · (Edited)
Here are the measurements as best as I can make in my shop:

Measurements (made at trunion):

Width: 1.614" / 41mm
Height: 1.889" / 48mm (trunion height - should be internal height of receiver)
Length: 14" / 355.6mm

Thickness of material appears to be 1.6mm (.064") at top groove in trunion.

Anyone have other numbers to post?
 
#3 ·
I believe two of the parts you show in your photos are the hinge ends for the feed pawl.

Photo 1 ) rough layout of the pieces
Photo 2 ) depicts 2 rivets for rear hinge half
Photo 3 ) depicts 2 rivets for front hinge half

I think you have 2 of the front hinge halfs in your parts - one extra
 

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#5 ·
been looking at my parts and the picture of the receiver from vltor. haven't taken any measurements yet. basically if you make a u shaped blank you can figure it out from there. Looks like you have all the basics figured out. I have been really busy doing conversion parts for the mg42, so I haven't had time to work on this yet.
 
#6 ·
Found this too:

http://club.guns.ru/eng/pkm.html

The receiver is a U-section stamped from 1.5 mm sheet steel and assembled by rivetings and spot weldings. The receiver has double walls made from two 1.5 mm plates welded one upon another. The receiver top cover is stamped from sheet steel and hinged at front to the receiver and locked at the back with a spring loaded latch. The ejector is similar to the AK's and riveted inside the receiver. The PK ejects empty cases through the ejection port located at left side on receiver. The ejection port has a spring-loaded dust cover. With proper gas selector setting, the ejection cycle is not as violent as the AK cycle and the PK won't damage ejected cases. The PK expels empty cases straight to left at a distance of about 1 m.
 
#7 ·
Pookie I saw a PKM Post Sample at the Chantily Va. GUnshow last weekend it was a Bob Landies from OOW. It was AWSOME! I asked the guy to open it up and let me look around inside of it. I was suprised by all the riveting and spot welding that has to be done to make one of these things. It makes a AK receiver look like child's play (and a small child at that).
 
#10 ·
Thanks, Ilya! I've updated my site & credited you for that find :)

I don't have that little detent, HOWEVER I was fondling the parts again and noticed that the cocking lever has a notch, and the cosmolene has a telltale sign of a spring that - apparently - resides to give the cocking lever handle spring resistance:

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1742.JPG

What do you think? A match?

That detent in your pic - it looks a lot like a part on my VZ-58 kit near the bolt stop. :dunno:

Edited - cross-posted... well you found that other part too! That's it... all parts accounted for. :D Now the fun begins.
 
#11 ·
Steelcore1964 said:
Pookie I saw a PKM Post Sample at the Chantily Va. GUnshow last weekend it was a Bob Landies from OOW. It was AWSOME! I asked the guy to open it up and let me look around inside of it. I was suprised by all the riveting and spot welding that has to be done to make one of these things. It makes a AK receiver look like child's play (and a small child at that).
Where's Chantily? Up north? I'm moving to Gloucester this summer, so I may be able to make it to those farther-away shows.

Yeah I'm realizing there are a ton more rivets on this sucker than an AK! Did you notice if there are internal rails?
 
#12 ·
Ilya, where are you getting these great pics, may I ask? :thumbup1:


My concern about this design is that it, like all open-bolt designs, is going to need a new trigger group to make it semi-auto. OK, that can be done, HOWEVER... where do you put it? The bolt carrier on this one is upside-down in comparison to an AK. THat makes it out of reach for a normal AK hammer. That's where it gets interesting. We can't use a REAL LONG hammer because the recoil spring is in the way! SO, I think something could be done to take an AK hammer and hang it upside down (from the top), and make an AK style trigger & sear that is REAL LONG to grab the hammer. I'm not sure how else to do this - yet. THAT will be the real challenge!

I wonder how the semi-auto M-60 MGs are built? There may be something there we can draw from.

Also, I think a brand-new firing pin will be needed too - I see no way around it. The existing pin is stationary while the open-bolt-firing bolt carrier drives the bolt home. Therefore, the factory pin is way too short for a hammer- or striker-fired closed-bolt design. I think the bolt is too long for an AK firing pin, however I have a lathe so I'm not too worried. I'll sacrifice a grade-8 bolt in the name of a PKM firing pin :D
 
#13 ·
I had 2 coil type springs in the kit I received. The larger one seems like a great fit for the charging handle. The second one (smaller and I think the detent I found on the ground might go with it) still has unknown function IMO.

Really don't remember where pics came from. Was just digging around looking at different forums and running down leads.

I loaded a few more photos in photo gallery section if you're interested.
 

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#14 ·
Well crap! I'm missing two parts now... that detent and that larger spring :( Looking at those other pics, I really really really wish I'd waited for the Hungarian kits. If they are around after I move, I'll probably pick up a 2nd kit.

The only area I can possibly thing a detent would be necessary is the bearing that locks the barrel into place. It is an overly complicated part, but it seem to be VERY loose when you think about its use. There seems to be no way to keep it in the "unlocked" position when changing the barrel. My guess is the detent is used for something around there, or possibly to lock the top cover into the open position. It seems to be REAL EASY to smash your fingers with the top cover when fiddling with the feed tray or the barrel lock, so maybe there's something there...

I was reading that site which said some of these came with recoil buffers - anyone have a pic of one? I'm thinking far-ahead that Blackjack Buffers could be tapped to make us some PKM buffers, but that's long down the road.
 
#15 ·
hcpookie said:
My guess is the detent is used for something around there, or possibly to lock the top cover into the open position. It seems to be REAL EASY to smash your fingers with the top cover when fiddling with the feed tray or the barrel lock, so maybe there's something there...
You know some things are really scary. I looked through the box and wouldn't you know it, I found that detent!!! The detent IS for the top cover!

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1743.JPG

It is really strong too:

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1744.JPG

:thumbup1:

OK, now I need to look through the box again to see if I can find that spring for the charging handle. If I can guess, the chargin handle locks into the closed position (all the way forward) and this spring keeps it in place. Otherwise it will get slapped by the bolt carrier if it dangles loose.
 
#16 ·
Cool - we've now found where all the unknown parts go. Good job - Thanks. I found the hole on the feed tray where the spring and detent go in my kit - good snag. All is well in the world.

Here's some pixs of the buffer for ya

BTW - I lucked out with MGS. Got four 200 rnd mags/belts and two 100 rnd mags/belts since that is what they advertised when I bought.

+1 for MGS for honoring their ad
 

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#18 ·
hcpookie said:
Where's Chantily? Up north? I'm moving to Gloucester this summer, so I may be able to make it to those farther-away shows.
Chantily is about 20 miles south of DC took me 2 hours to get there but worth the drive. Its about 5 min. from NRA HeadQuarts and the National FireArms Musemn

Did you notice if there are internal rails?
Yes I did ,I was looking for those and Yes it does have 2 sets of rails something like an AK. The ejector is built into the top rail, it's riveted and spot welded in.
 
#19 ·
Illya Kuryakin said:
I was just thinking that I didn't see a top cover spring in your photos on your site. Didn't know if you had one.

The dog leg side of the spring fits into a cutdown area on the top left side of the trunnion behind the cover hinge pin.
No, I don't have one of those. Spring #3 to add to the missing parts list. I'm going to shake out all the wrapping paper - again - and hope I can find these springs. Otherwise I'll have to scrounge around the hardware stores :( Is the smaller torsion spring location correct, in that it fastens to the hinge for the feed pawl cover on the RH side? I don't think it would work for the top cover, so I'm pretty sure my top cover spring is missing.

Yours is a Hungarian kit, right? I got the Romy kit for $1150 which didn't have any accessories. I got the tripod & bipod but no carry strap, cleaning kit, or ammo stuff. I can get ammo stuff so I'm not worried about that, but the carry strap and cleaning kit are a different story. Did you notice how the little oiler is attached at the buttstock? Very cool!
 
#20 ·
Here's a photo of most of the small pieces that came with the kit (As I remember the detent and top cover/feed tray pin are both not in this photo). You can see the 2 torsion springs for comparision of size/shape. I believe you're correct with regards to the smaller torsion spring attaching to the feed pawl cover pin.

BTW - Top cover spring reads 0.082 diameter spring material

Kit I received is Hungarian. It was expensive but in new condition. Oiler is very cool :)

If you find a place that has the attached 100 rnd cans/belts, please let me know. I'd like a couple more of the 100 rounders.
 

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#21 ·
I'm interested to see what you guys are going to do for the striker/hammer for this thing. It's a beautiful weapon, but there's not much room left in there...


.
 
#22 ·
Yeah well if you can find where to get stuff like the carry strap, drop case, and all those tool things I'd like to know too!

I wonder if the 200-rounder box lids can be cut & re-welded to 100 round size? I read the boxes are aluminum so maybe not...
 
#23 · (Edited)
Rhino_66 said:
I'm interested to see what you guys are going to do for the striker/hammer for this thing. It's a beautiful weapon, but there's not much room left in there...


.
I'm thinking some milling will need to be done to remove material around the sear. I think either the hammer can be connected above the bolt carrier and swing down to hit the firing pin, and the sear (disconnector) would be mounted somewhere directly behind the bolt. Assuming that there is enough room to clear the bullet extractor claw that removes the bullets from the belt on the backward motion.

That would make the need for a trigger that had a long L-shaped bar attached so that it would reach up beside the carrier and touch the sear. Another option would be to make a VZ-58 style of mechanism that is striker-fired. You'd need a long trigger arm no matter what.

I don't see any reason that would couldn't make the receiver 1/2" longer to make room for the parts.

I think there will be some work involved to shim or block the receiver Uzi-style so you can't insert the original bolt carrier into the receiver. That means milling a notch into the carrier like on the Uzi or like the 1919a4 semi that lets only the semi carrier fit.

It will be a challenge to be sure! I was surfing Weaponeer's ATF letters forum and found that is kinda what the M60 semi conversion did/does:

http://www.weaponeer.net/forum/forum_posts.asp?TID=1110&PN=1
 
#24 ·
A few more design ideas. Thinking about the blocking shim that prevents insertion of a FA bolt carrier, there is some room on the left side of the bolt carrier that would be suited for this. In this pic, the area I'm suggesting is directly below the "194" at about the 6" mark on the tape measure:

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1746.JPG

The area would need to be matched to the extended part immediately to the left of the tape measure. That would allow us to put a blocking shim on the left hand bottom of the receiver and it would be about 1/4" high. I think it wouldn't have to be any more than about an inch or two long, and it could serve as a lower guide rail if it were long enough to support both of these extended segments.


The sear engagement notch could also be ground off, since it would be moot. However, the bottom of the bolt carrier is worn smooth, suggesting the carrier touches either the bottom of the receiver, or more likely, a spacer to keep it off of the rivet heads for the trigger frame.

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1747.JPG

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1748.JPG


I don't think the trigger frame could be moved backward or forward. The trigger has a lug on the front that engages a mating tab on the tripod. Therefore the trigger group should stay in the original location. The good thing for us, is that the tripod mounting arrangement will help to confirm that the trigger frame is at the proper position!

Here, you can see where the measurement I'm getting is 5 11/16" from the rear of the receiver to the front of the mounting lug (the tape measure is set to 10" at the rear. That is as far forward as it can go and still be mounted on the tripod. The locking tab on the tripod would allow it to be moved back 1/16" with no problems. At about 1/8" it may no longer engage unless the tab on the tripod is modified.

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1749.JPG

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1753.JPG

http://pookieweb.dyndns.org:61129/beltfeed/PKM/DSCN1754.JPG
 
#25 ·
This would be a perfect case to get a letter from the ATF for classification. The MG42 was determined to be a "firearm", not a rifle. It is shoulder supported, not shoulder fired. As such, it is not a semi-automatic rifle and is therefore not subject to 478.39 for parts count.

Since there is no forearm to support the front of the PKM, it would most likely be classified as a "firearm" instead of a rifle.

The sear notch could be milled with a bevel to eliminate any possibility of it catching on the sear.

With the rear block being riveted, that kinda limits what you can do. If it were removable (like an HK buttstock), you might be able to come up with a striker to ride in a set of rails. There would still be a problem with needing a guide rod to keep the spring retained.

If the guide rod is attached to the striker instead of the rear block, it could be pushed back through the block and into a hole in the stock (think of the rattail on a FAL carrier).

For a sear, you could mill a latch mechanism to attach behind the buffer plate. If the sear lays horizontal, a vertical arm could pull it down on the back end of the sear to pivot it off of the striker. To connect the vertical arm to the trigger would require a horizontal arm. By adding a hump to the horizontal arm, you would effectively have a disconnector (like a Sten trigger bar). Does that sound convoluted enough?

I wish these kits weren't so expensive. I think it's a really beautiful weapon, but I can't float the coin for one.
 
#26 ·
Yep, I had considered the same thing after looking at my VZ kit. I measured the buttstock earlier and you have a good 4" of useable buttstock behind the rear stock tang. There is just about 5 1/16" in-between the rear of the bolt ( in battery) and the back of the receiver. Not sure if that would work.

Assuming it won't, I'm thinking about something that imitates the general action of a semi AK, but along a different geometry. I'm going to make a pic to explain, it is too involved to try to type out...
 
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