KEEPING IT TIDY
Guide by J. DeFazzio
The PM-63 has flooded the surplus parts kit market for many years now. The prices have been kept low by two factors – lack of barrels and a lack of a consistent method of semi-auto conversion. Luckily barrels have recently flooded the market, and I believe that I have found a very consistent method of semi-auto conversion. I’m open to all criticism, questions, and nagging thoughts that anyone has. Please contact me directly at my email. Videos available at the end of this article.
The PM-63 frame is very simple in the eyes of a homebuilder or 07 manufacturer, but rather interesting to a machinist. It is in essence an overgrown pistol frame, milled out of a solid block of steel but some of those milling operations are wildly complex. The main differences are in it’s C93-esque rear appendage, original method of operation, and barrel retention interface. At the rear, you’ll find the folding stock socket and locking features. The original method of operation is open bolt full-auto. The barrel retention is achieved by a system akin to the CZ27 pistol where the male fins on the barrel rotate into the female surfaces on the frame directly in front of the permanent feedramp.
Some of these features have been the bane of home builders and 07’s alike, since as a whole unit they don’t leave much room for the guts of a semi-auto conversion. Many have tried striker fired set ups using the original rate reducer claw and counter weight. Others have tried VMAC hammer set ups. Others have also tried AK FCG’s. What all these conversions have in common is an exposed transfer bar leading from a modified original trigger back to whatever style of guts they prefer with a large and rather ungainly hole in the frame. I personally never liked having the guts of a build hanging out, so I set out in this build with some things to accomplish –
- No external transfer bar
- Closed bolt, semi auto only
- Keep the appearance as close to the original military firearm as possible
- Hammer fired
- Carbine length
- .380 ACP caliber (still working on that)
THIS IS MY OWN PERSONAL EXPERIENCE, NOT A DEFINITIVE GUIDE. YOUR MILEAGE WILL VARY FROM MINE. THINK OF THIS DOCUMENT AT A SET OF TRAINING WHEELS FOR YOUR OWN BUILD.
ALL NFA RULES APPLY.
WHEN IN DOUBT, LUBRICATE.
Step One - FRAME
Its very important to pay attention to which kit you're selecting when attempting a full reweld. Sometimes when looking for kits online, you'll find some with rock bottom prices but only to find that the most critical geometries have been completely destroyed. In the PM-63, that spot is the barrel mounting area and integral feedramp. These areas are critical to functionality and can be very difficult to rebuild and remachine once cut. Luckily, since the PM-63 is essentially an overgrown pistol, it can be rewelded with very little in the way of fixturing. A straight edge is realistically the extent of most fixturing required, however there are jigs available for those looking for a more "guided" welding experience. Frame distances can be taken directly from the slide as well.
Before the welding the frame together, it is paramount to make and install denial features so a MG isn't created in the process. Since the PM-63 utilizes an original sear catch on the slide, this needs to be ground off. At the same time, this original sear catch cannot reciprocate anymore through the frame, so I cut off the tip of the original sear and welded it into place. This process ensured that not only could the new frame never accept a full auto slide with an original sear, but it also closed off the spot where the original sear would've sat which effectively killed two birds with one stone.
With this done the frame can be welded back together. Once it's together and checked for warp, the slide can be lapped back into place. I prefer to use valve grinding compound from the auto parts store. It's water soluble and gets finer as the process continues. A keyseat or Woodruff cutter of the appropriate diameter can also be used in place of final lapping.
Step Two - FCG
I used an IO PPS-43 FCG. Originally, it is designed to fit directly into a stripped PPS lower with little to no modification required. Seeing as it is a 100% self contained FCG, I decided it would be perfect to use. I cut it down to size, leaving off the trigger and linkage as well as the front ½”. This let is sit almost perfectly into the rear cavity of the frame after removing the rate reducer, safety, and bolt hold open.
The problem at this point is that the entire FCG sat too high in order for the hammer to complete it’s length of travel. The rear of the frame was milled not only wider, but also deeper, removing the shelf that was the rate reducer’s travel limiter. The pocket needed to be wider in order to clear the FCG’s pivot pins. After everything was fitted and finalized, the FCG was riveted into place in the pocket. With enough ingenuity, it’s 100% possible to have the FCG components on their own permanent pins in this frame section, negating the need to mill this pocket wider.
Step Three - SLIDE
The slide is incredibly simple. A fixed firing pin with the reducer pucks in the back half. This gives a lot of room for the required cut and new floating firing pin.
The rear half of the slide containing the rate reducer bits needs to be milled out to allow the hammer to fall. Along with this cut, the very rear of the slide will need approximately ¼” cut off in order to clear the hammer for disassembly and reassembly. For the floating firing pin, there are many ways to skin a cat. Below is a drawing of how I did mine.
The trick here is to bring the end of the firing pin farther rearward in order for the hammer to strike it. This was accomplished by turning a piece of 1018 to size, epoxying and detenting into place. The off center hole was drilled from the breech face after removing the hardened fixed firing pin. An aircraft extension drill is the only way to do this. They’re cheap. The firing pin was made from O1 drill rod and cross pinned into place with 0.050” travel. While all of this work was going on, the end of the feeding surface that was now even with the firing pin face was radiused to easily reset the hammer. The hammer face was also reprofiled to ease the amount of friction and force required to reset.
Step Four - INTERNAL TRANSFER BAR
Now that the FCG and the firing pin was all done, the second to last step was to make it all work. Contrary to popular belief, there is a ton of space in the frame forward of the magazine well. Its just a matter of how you utilize it. In the drawing below, you’ll see how the recoil spring guide rod interacts with the trigger pocket.
In this rather cartoonish drawing, you can see that the recoil guide rod sits on a very small shelf directly in front of not only the trigger pocket, but also the barrel retention surfaces above. The head on drawing shows it a little bit better. In order to make a transfer bar fit in the frame along side the trigger, some of that shelf needed to be removed. The dicey part of this process is doing exploratory cuts into the frame to find that shelf (since I didn’t really have a fantastic way to measure for it). Using HSS slitting saws, a plunge cut was made directly in ahead and right of the barrel retention surface. Luckily, first times a charm and the recoil guide rod surface was removed and a space big enough to wiggle something next to the trigger was created at the same time.
As a quick reference, the visible hole in the frame is where the recoil guide rod will bottom out. This is exactly what I wanted. The next step involved milling out the surface next to the plunge cut as pictured above. In my opinion and experience, its okay to cut into that retention area. There is more than enough there to retain the barrel. The drawing below shows where the plunge cut took place. After these two cuts were made, the trigger from the IO PPS-43 FCG pack was used since it already had the same size pivot pin hole and the hole for a transfer bar. Since the trigger is slimmer than the original military trigger, a shim was added alongside to take out slop. At this point I made several different transfer bars out of 316 filler rod as seen in the photos.
I ended up using a piece of coat hanger wire bent in the same fashion as the photos. Even though that wire is much heavier gauge than the weld filler as pictured, it was still small enough to create lots of slop in the system. To fix that, I made “bushings” for both points using autoclave Teflon tape. This is actual Teflon, not pipe thread tape, meaning it will never have to be lubricated at those two points and will always keep true to size. The final iteration of the transfer bar set up is pictured below. With the bar in place, the hammer dropped no problem. This was now closed bolt semi-auto only. The last piece was the barrel.
Step Five - BARREL
Simple. Turn down original 5.5” barrel, add turned down extension. Weld. Paint if desired. This was to keep the firearm carbine length meaning the stock and foregrip can be used without need for a Form 1. OAL must be longer than 26” stock extended and barrel 16” or longer measured from beech face.
Step Six - TEST FIRE
This didn’t go very well. Lots of failure to eject, some runaways, and lots of frustration. I did notice the trigger was very dead and spongey. Along with that, the FCG developed hammer follow. FreedomMachine noted it was more than likely the disconnector needed some attention to come farther downward and hold the hammer. I also suspected the sear spring in the pack wasn’t strong enough to reliably drive all of the new trigger components. I had a similar issue with my PPS-43/52 build. The disconnector was addressed and reliably held the hammer and released it onto the sear after some honing. One leg was longer than the other. The original sear spring was swapped with a ¾ long AK FCG disconnector spring. This not only made the sear “snap” in to place, but also really improved the trigger pull. Lastly, a tapered coil spring was added to the end of the recoil spring guide rod, putting a lot more positive tension on the trigger to begin with. It felt almost like a medium price point trigger at that point. Not awful, but also not great – 3.3# pull. The firing fin was lubed with graphite.
The magazines retain the ejector for the PM-63. They are the taller side of the left side feedlip. At the range I noticed that every mag had that area bent differently. Back at the shop I messed with them for a while only to discover – that wasn’t the problem. None of the mags were sitting high enough. When I welded on the end of the mag well, I measured it using a magazine. The problem with that was I didn’t clean either the mag or the parts kit when I took that measurement so it came out long. After one spot weld on the magazine catch profiled to shape, every mag fit perfectly and ejected perfectly. Second range trip time.
Step Seven - FINAL TUNING
To my surprise, it ran like a top. Magazine after magazine, after magazine of all sorts of different ammo. Norinco FMJ, Prvi FMJ, WOLF FMJ, S&B sintered steel FMJ, all of it with no problem. The trigger still feels great, the hammer reliably resets and strikes, and no run away.
This build is now a completed semi-auto closed bolt carbine that is hammer fired with an internal transfer bar. The .380 conversion will happen once I can get a liner.
Conclusion
The days of super cheap barreled AK parts kits may be over, but we've recently entered an era of incredibly cheap sub gun kits. Most of these get cast off to the side due to their lack of proven semi auto conversion and the complexity of jamming a new OS into their cramped frames. This project has been one of my favorite not only for it's functionality, but also in the way that it proved what others had said was impossible was in fact possible. There's far too many people in the building community that will look at a cheap parts kit and say that it's impossible to get running again with a clean and tidy design. I set out to prove those sentiments wrong and I'm very glad that I did - this PM-63 quickly became one of my most reliable builds and gets taken to the range regularly. Many of you have seen this either from WeaponsGuild, r/GunnitRust, the YouTube Channel, Odysee or on my Instagram page and I hope that this guide has broken down the process into a very simple how-to.
The Cold War Era produced massive volumes of sub guns of all different calibers and models. The Polish PM-63 would fit into any collection with ease and is a real head turner at the range. I highly recommend picking up a kit, a FCG pack, and building one - as with all kits, they're not getting any cheaper!
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