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PPS-43 SBR Build

143K views 67 replies 12 participants last post by  Aggro 
#1 · (Edited)
My next project is going to be a PPS-43 semi-auto Short Barreled Rifle.

USPS delivered the reciever repair section on Friday. The parts kit and barrel trunnion should be here within the next few days. Form 1 will be sent out shortly along with the $200 check.

I ordered the reciever section from www.Stenparts.com

It is mild steel .070" thick and 14" long. It is a nice piece, and does come with the trunnion support even though the website doesnt mention it. It came with an unattached template for cutting the ejection port and locating rivet holes. Cost was $50 plus shipping.

Left and right sides. Trunnion support is on bottom left of template.





I ordered the parts kit and trunnion from www.Gunthings.com . The price is a bit higher than most places, but unlike the others I found, this kit comes with the original 10" barrel.

Pictures from his site, actual pictures will be added once I get the parts.





I want to keep the gun as original as possible. Some changes will have to be made though. The bolt will have to be modified to work in a closed setup. A blocking bar of some sort will need to be added to the reciever and the bolt modified to clear it to prevent a full auto bolt from being used.

A new FCG will be needed. I want to try and keep the original trigger. There is talk of using modified Mac and AK FCG's, I may just make my own.

I cant do much of anything until the Form 1 is approved, so it may be a while before this gets any serious updates.
 
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#4 ·
Time for an update -

The parts kit came in from Gunthings.com and I'm very happy with it. The lower assy. looks to be new/unused. There is no wear on the moving parts, contact surfaces or finish.









The barrel is in great shape, bright and shiny with sharp rifling. The folding stock assembly and all other parts are used and in great shape.



 
#5 ·
I also ordered the barrel trunnion and support from Gunthings.com

The barrel to trunnion fit is good as is the trunnion to trunnion support fit. The trunnion support that came with the reciever section from Stenparts will not be used, since it is slightly bigger and doesnt fit up to the trunnion very well.

New barrel trunnion



Trunnion with support



Stenparts trunnion support on left compared to Gunthings on right.

 
#10 ·
Ok. I have the bolt disassembled and I have a few ideas floating around in my head about how to make this all work.

Extractor and firing pin removal is easy. Depress the extractor plunger and the extractor will fall out of place with a slight tap. Pull the extractor plunger and spring out.



Tap the bolt face down and the firing pin will slide out.

 
#11 · (Edited)
Ok.. now a few questions on some things I'm not 100% sure about.

Since this will be a registered SBR, does the parts count BS still apply? EDIT - I did a little more digging and found that NFA items do NOT fall under 922r. So I dont need to worry about the parts count.

If I can, I would like to cut the bolt behind the cocking handle and use the rear piece as a striker. The front part would be the bolt and would operate just like any other closed bolt setup, but the striker would be held back until the trigger is pulled.



Plans are to have a blocking bar welded into the underside of the top of the reciever, bolt clearanced on top to clear the blocking bar, and bolt cut in half and converted to either AR-15 or home built firing pin.

What I'm wondering as far as legality goes is, can I still retain the original trigger and sear to operate the striker? Or does ATF view this is a violation even though an original FA bolt will not work because of the blocking bar?

If there is any grey area there, I will probably just mill the sear catch off of the underside of the bolt and replace the original sear with a modified/homemade version that will not remotely work with a FA bolt.
 
#12 ·
batfs main concern is that you cannot readily install original FA parts into your receiver.
if you have a blocking bar, sounds good...if the bolt is cut in half and the back half if the hammer, how is the front half going to be spring loaded to the closed position? how is the back half going to be spring loaded without interferring with the front?

I have an answer, just seeing if you have thought this far ahead...
 
#13 ·
I was thinking two seperate recoil springs side by side. The spring for the bolt would pass through the striker to the back of the reciever. The other spring would sit against the back of the striker and to the rear of the reciever.

I think I can reuse the original recoil spring assy. for the bolt. I will have to modify the striker to let the bolt spring and guide rod pass through. The two guide rods will help guide the striker to the bolt after the trigger is pulled.

I really need to sit down and put pencil to paper and see how this all will work, but I have a general idea.

What was your idea?
 
#14 ·
Nevermind on modifying the striker portion to clear the bolt guide rod and spring.. it already is :homer:

Anyways.. I will need to drill a hole through the right side of the striker for the other guide rod to pass through.

I'm also starting to wonder if the orignal rate spring will work ok with the modified/lighter bolt and striker :confused:
 
#16 ·
Well I cant figure out a way to integrate a disconnector into the original PPS-43 fcg... The way everything is hooked together and the small size of the reciever doesnt leave much to work with.

I disassembled and removed the PPS fcg last night and pulled the fcg out of my AK to see if I can make it work. It looks like it will work OK, but the bottom of the bolt will need to be milled to clear the trigger hooks. This would mean I would not be using the striker setup.

In the weaponner build thread PBB mentioned using a Bren gun style fcg, but I cant find a decent diagram of the setup. If anyone has a detailed schematic of the Bren fcg available, post it up please :D

I'm going to try and re-use the original safety with the AK fcg... I have an idea on how to do it, but I need to get the AK fcg in there first. If I use the AK fcg, I'll probably cut the AK trigger off and weld the PPS sheetmetal trigger onto whats left so that it looks original.

Pictures in a little while...
 
#17 ·
we once did a similar mod, cut bolt behind cocking handle so both parts are moved when cocking, the rear section stayed behind while the front section went into battery. the original spring ran the front part and a second spring AROUND the first ran the back half. the seciond was light weight, just enuff to fire the bullet.

I am looking into shortening the whole receiver and cutting the bolt down,then remaking the sear catch notch under the cocking handle then using the orginal FCG minus the safety...
first pic shows somewhat teh new location for the magwell...
secong pic shows somewhat location for everything to fit together...

I have WAYYY tooooo many parts and not enuff time to cobble more shit together...
 

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#18 ·
I am looking into shortening the whole receiver and cutting the bolt down,then remaking the sear catch notch under the cocking handle then using the orginal FCG minus the safety...
first pic shows somewhat teh new location for the magwell...
secong pic shows somewhat location for everything to fit together.
Cool project.. What are you going to do for a disconnector? Or is this going to be a FA?

I have WAYYY tooooo many parts and not enuff time to cobble more shit together...
I've got a solution... I'll be driving up near the WTF/Dallas area on Monday. I will gladly swing by and "dispose" of any parts you have laying around :D
 
#19 · (Edited)
this will become another dealer sample that I cannot sell or give away...but can test fire and demonstarte til it falls apart.


wf/dfw "area" is a bit generalized...I'm about 100+ miles from dfw...


I am currently tinkering with at least SIX differnet pseudo weapons, PLUS working on Suomi bolts for several peoples, plus making rubber coated aluminum wheels for the 1/6th Stuart RC tank, making Delrin trans gears for the same tank, and trying to keep three concubines happy while supporting my wife.



I really think this gun is too ling even for its intended purpose...I guess small MACs and small uzis have spoiled me


you can alwya mill out the underside to allow ak/ar hammer to fit inside to strike a floating firing pin...check the Suomi thread at weaponeer to see what I am talking about...
put an ak/ar fcg in the pps receiver...
 
#20 ·
wf/dfw "area" is a bit generalized...I'm about 100+ miles from dfw.
I'm going to Sherman to pick up a lathe, then heading through Plano/Dallas on the way back.


you can alwya mill out the underside to allow ak/ar hammer to fit inside to strike a floating firing pin...check the Suomi thread at weaponeer to see what I am talking about...
put an ak/ar fcg in the pps receiver...
Thats what I was talking about a couple posts up.. Using the AK fcg and milling to bolt to clear the hooks and hammer. It looks like the left side of the bolt will have to be damn near milled up into the recess for the recoil spring. Hopefully that wont cause any problems.

I should be able to get a bit done by Tuesday as far as the bolt and fcg goes once I get the lathe going.
 
#23 ·
Got a bit done tonight.

The inside width of the reciever measures 1.040" and the AK hammer measured 1.055" wide at the cross pin bore. I turned the hammer down to 1.010". It fits nicely in the reciever now.

Next I marked and cut the left side rail for hammer clearance and for access to drill 2 of the spot welds holding the trigger/sear bracket in place. There were 4 spot welds and 1 rivet holding it in.



I drilled them all just far enough to break through the bracket without going through the floor of the reciever. The bracket came off easily once all the welds were broken.



Next I demilled the trigger/sear assy. It has a pin that is slipped in from the right side and then spot welded into the left side. I drilled the left side with a 3/16" bit until the pin was free. I plan on reusing the trigger with the AK fcg.





Tomorrow I'll start fitting the AK fcg into the reciever.
 
#24 ·
Got a bit more done the last 2 days.

I chucked the bolt up in the lathe and drilled as far as I could with a regular 11/64" bit from the backside of the bolt. I drilled the existing firing pin pocket all the way through to the recess for recoil spring guide rod. Picked up a 12" long bit today to finish drilling through the backside. I was worried that the holes would not meet up correctly, luckily they lined up just fine.







Next, I roughed out the bottom of the reciever to clear the AK trigger. I had to get the trigger to sit down as low as possible to keep from having to mill too much out of the bottom of the bolt to clear the hooks and hammer.

 
#25 · (Edited)
Next I located the trigger pin holes and drilled them undersize to 3/16". I used a reamer to open them up the last little bit until the trigger pin fit through snugly.









AK trigger in place, hammer is not located yet.



You can see about how much will need to be milled from the bottom of the bolt. Not as much as I originaly thought it would need.



A view from the backside of the bolt. It's not in the closed position, it sits quite a bit further forward.

 
#27 ·
It needed to be that far forward to be able to hit the firing pin correctly... any further back and it would be hitting the bolt too low. It was either place the trigger that far forward, or make the firing pin stick out of the back of the bolt another .5" or so.

The AK trigger is getting cut off of the pivot/hooks and the PPS trigger welded back on, so I have some wiggle room as far as trigger placement goes.

Hope that makes sense. :D
 
#29 ·
Alright.. Made a bit more progress. Ran into one problem which I think is a simple fix/modification.

To get the hammer placement correct, I made a jig out of 1/4" steel with the correct spacing from the trigger to hammer pin. I measured the CTC distance from my AK that I robbed the trigger group out of. It measured 1.565" CTC.

The larger hole was drilled to 3/16" and reamed to accept the trigger pin which is about .195" dia. The other hole is 5/32" which fits my center punch perfectly. I got my vertical measurement by measureing to the lowest point on the hammer from the center of the hammer pin bore. It sits .315" above the bottom of the reciever.



Hammer and trigger installed



Hammer fully depressed



And all the way forward

 
#30 · (Edited)
I had to file the trigger rests to let the trigger sit further down against the bottom of the reciever in the rear. I still may file it some more if necessary later. The trigger hammer and disconnector are all working correctly.





Hammer held by trigger



Released



Hammer being held by disconnector



Hammer held by trigger after releasing from disconnector



In the last pic you can see why I'll probably file the trigger rest down some more. By letting the trigger rotate back more, I will get more engagement between the trigger hooks and the hammer.
 
#31 ·
I went ahead and drilled the cross pin for the recoil spring guide rod also. The firing pin will be going through it. I installed it in the bolt and clamped it in the vice, then drilled an 11/64" hole through it using the firing pin bore as a guide.

I pullled it out of the bolt and drilled it to 3/16" to make sure there is clearance for the firing pin to travel through.



Backside



Bolt, recoil spring and FCG in place



Here you can see the problem. When the hammer releases, it is blocked by the recoil spring and guide rod. The only solution that I can think of is to cut the left side hammer ear off, effectively making it a single hook setup. It will clear fine once that is done. Any reason why this shouldnt be done?

 
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