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 Hudson's PPSh 41 Reborn

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Cerwyn
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PostSubject: Hudson's PPSh 41 Reborn   Wed Aug 11, 2010 1:57 pm


PPSh Reborn



Most of the regular visitors here will recall my post explaining the catastrophic failure of my Hudson PPSh 41



During firing, the lower receiver snapped clean in half, with spectacular, if jaw-dropping results. Bits of very expensive Modelgun were spread about over my floor in a seemingly irreparable heap. Hereís a video of THE moment:




Fortunately for me, forum member 8ace came to the rescue and managed to not only repair, but strengthen and improve the whole model.



The main damage was to the lower receiver, right at the magazine well. Looking at the casting, this has to be the weakest area of the whole model and itís hardly surprising looking at it, that the casting snapped here.






As the casting is Zinc Alloy, it will not Weld as does steel. Zinc Alloy like this melts at much lower temperature than steel and most welding and brazing rods so that was out of the question. There are low temperature Alloy welding materials available, ďMuggyweldĒ for example, but even if welding could be considered, thereís so little metal making contact at the point it broke itís highly unlikely a join would have held.



Strengthening plates fixed inside the receiver to bridge the break seemed to be the answer. Steel is the best option for a solid, strong repair so 8ace came up with the idea of making a steel cage that would be fixed inside the receiver. Fortunately, the PPSh has a large lower receiver with ample space available to fit plates inside without fouling the Bolt and magazine.



Hereís the cage:




cut from 3mm thick steel and welded together, this is placed inside the receiver like this;






Twelve recessed bolts (six per side) plus the four ejector plate screws firmly hold everything together plus the cage is "welded" to a base plate which is fixed under the ejector zinc body, hopefully the steel will take all of the stress with the zinc as just an outer skin.

Once the receiver and cage were bolted up, the bolt heads were covered over with filler, sanded smooth and painted over making for an invisible repair. It really is a very tidy repair job undetectable from the outside, as you can see here:





Hudsonís models arenít known for their good firing performance, the standard PPSh is no exception. Miss-feeds are common, the cartridge nose failing to enter the chamber centrally and jamming against the outer face.

Having the steel cage shaped around the magazine well presented the perfect opportunity to cure one of Hudsonís design faults, the loose fitting drum magazine. A new, closer fitting well was shaped which now holds the drum snug. No more wobbling rattling drums. Stopping the drum moving helped cartridge feeding during firing no-end too.

The Detonator Chamber itself was found to be out of line with the bolt face by just over a millimetre. Ideally, the bolt face centre should be dead in line with the centre of the Detonator Pin tip. This allows for a perfect line for the cartridge to be pushed from the magazine by the bolt straight into the chamber making the Det.Pin enter the cartridge nose dead centre.

Hudson had mounted the chamber so that its centre lay higher than the bolt face. Re drilling the chamberís securing screws brought it back to the centre line.

This photo shows the space created between chamber and receiver once it had been repositioned correctly





A gas by-pass system allowing smoke to pass from the chamber through the barrel used to be a standard feature on Hudsonís PPSh but my model didnít have one. Iíd been convinced all along that because the chamber in mine didnít vent through to anywhere it was hardly surprising that one drum of 40 cartridges would create enough dirt and debris around the Det.Pin and chamber walls that any attempt at a second magazine would always result in jam after jam as cartridges stuck onto the Pin failing to extract.

Thankfully, Hudsonís tooling dies still formed barrel castings with blanking hole positions for the original gas by-pass facility. The barrel was drilled just deep enough to pierce through. The factory had permanently inserted a hardened steel anti-tamper bar at the base of the barrel which prevents further drilling but enough of a vent is there to allow smoke though. The hardened bar can be seen in this next photo together with the new drilled holes





The chamber was also drilled in line with the barrel. Next a flat plate was made to screw over the two holes, a groove milled into one side to act as the gas by-pass channel.





Last job was drilling and tapping screw holes to fasten the plate in place.




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JohnnyV
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PostSubject: Re: Hudson's PPSh 41 Reborn   Wed Aug 11, 2010 2:20 pm

Fantastic Job!!
As they say "necessity is the mother of invention" and this proves it!!
You have GOT to do a video!!
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Cerwyn
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PostSubject: Re: Hudson's PPSh 41 Reborn   Wed Aug 11, 2010 3:42 pm

Thank you John All the credit for this superb repair must go to 8ace. His ingenuity saved the day for me again with this one.

A Video is most definately on the cards

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PostSubject: Re: Hudson's PPSh 41 Reborn   Wed Aug 11, 2010 4:48 pm

Great job! I could think of the theoretical part, but execution is quite another story. What has been done here looks neat, clean and functional - well done!

Every modelgun collector should have their own 8ace =)

Quote :

cut from 3mm thick steel and welded together, this is placed inside the receiver like this;
This part goes INSIDE, and holes we see on the outside are drilled in the original receiver, right?
For a moment I was confused with outside/inside placement, as original receiver does not have holes in any other picture.
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Cerwyn
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PostSubject: Re: Hudson's PPSh 41 Reborn   Wed Aug 11, 2010 6:03 pm

smootik wrote:
Great job!
Every modelgun collector should have their own 8ace =)

Absolutely, I couldn't agree more. He's saved my modelgun collection and my sanity more than once

Quote :

cut from 3mm thick steel and welded together, this is placed inside the receiver like this;

This part goes INSIDE, and holes we see on the outside are drilled in the original receiver, right?
For a moment I was confused with outside/inside placement, as original receiver does not have holes in any other picture.

Yes, the steel cage sits inside the receiver. Holes were drilled and countersunk through the original Hudson receiver, bolts passed through to thread into the steel cage.
Bolt heads were ground flush with the outside surface of the Hudson receiver then hidden with epoxy filler.
Once smoothed out and painted, any evidence of the bolt heads has been well hidden.

The steel cage holds both parts of the broken receiver together. There simply isn't enough Zinc material at the break point to hold together or support any weight.

It's a very strong, tidy and ingenious sollution which might rescue other Hudson PPSh41s in future

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8ace
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PostSubject: Re: Hudson's PPSh 41 Reborn   Thu Aug 12, 2010 8:05 am

Quote :
Absolutely, I couldn't agree more. He's saved my modelgun collection and my sanity more than once

Doesn't do my sanity any good when you guys don't play nicely with your toys Rolling Eyes lol! still keep the grey matter exercised

It couldn't have broken in a worse place No I have the capability to braze zinc parts together cheers but not when they are in a highly stressed area. It's a bit of an overkill repair Shocked but it shouldn't break there again Suspect
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Jakes-model-guns
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PostSubject: Re: Hudson's PPSh 41 Reborn   Thu Aug 12, 2010 9:23 pm

BRILLIANT well done the both of you.
Does she work well?
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