Gas-Operated, Semi-Auto, Magazine-Fed APS Shotgun

[Katotaka]

Looking at the bolt photos I suspect you could make one out of POM round stock, without layering PVC tubes which could be point(s) of failure under repetitive impact and stress cycles.

[CatgutViolin]

Looking at the bolt photos I suspect you could make one out of POM round stock, without layering PVC tubes which could be point(s) of failure under repetitive impact and stress cycles.

 

I wanted to just do that, but it needs a groove for the extractor and disconnect, plus cutouts to clear the magazine. If I had a mill it would be a piece of cake, but with just a drill press, layering seems the best way to get the complex shapes I need.

 

In any case, the new bolt is using aluminum tubing for the lip (the part that strips rounds from the mag and encircles the recessed bolt face), while the gas tube I've rebuilt as a narrow aluminum tube nested inside a copper pipe plug which is rammed into the central PVC layer, and the gaps filled with JB Weld. Basically, I'm now using aluminum tubing to handle impact on both ends, and the PVC will just be acting as a spacer, so I'm confident that this design will hold up once I get it all together.

[CatgutViolin]

I have spent twenty hours since declaring the project 'done' actually getting it done. It turns out that there's an issue with the shells rimlocking in the magazine which is solved by having high spring tension. After rebuilding the bolt and getting a better gas seal in it, I added another recoil spring, and switched out the homemade magazine springs for slightly cut down (~75% of original length) Saiga springs. I also adjusted the extractor yet again, but feel confident that this one will be the last.

 

Some of these changes were made after an attempt to record a proper demonstration video, which I decided to save for humor's sake:

 

 

But now I tentatively think it's actually done.

[hitmanNo2]

You have tremendous patience.  I think I would have thrown it out of the window.

[vietnammarine]

Congrats! Looks great.

 

Especially like the mag cuts, they are adding a lot to visual aesthetics

 

 

Sent from my iPhone using Tapatalk

[Brigg]

I had a good laugh at the video. It never fails that after you hit record, every possible problem, including new ones will find their into the video. When I tried to record the video for my smg the other day I had a whopping 34 malfunctions. None of which I had seen since I finished the internals months ago. And none of which I could reproduce when the camera was not recording.Most of which were light strikes or the bolt refusing to cycle after firing a round.

 

The only thing more effective at making issues crop up is to try to show something in person. That's like a guarantee that every screw will come loose, every o-ring will have shrunken, and every part that could conceivably fail will.

[CatgutViolin]

Thanks guys. I've done additional testing with both the short and long barrels and they seem to be working properly. The only issues I'm occasionally seeing are all due to heavily worn/damaged hulls not feeding or magazines with weak springs binding up.

 

It seems that the Saiga mags actually work best with their original springs, not cut down at all, which is a bit of a problem as I'd already cut down the springs on 4 of the 5 mags. Whoops. I have replacements on the way, as well as a CSSpecs 8rd steel magazine arriving today. In the meantime, I can combine two of the cut-down springs with a spacer and get good performance, so I really have three functional mags, which for a gun like this is more than enough.

 

So, I'm currently planning to head to the local field this Sunday. Stay tuned for some gameplay footage.

[SpecialWeaponsAndPlastic]

CatgutViolin: Amazing work as always. Funny video, and I'm glad you got it to work in the end.

 

A small contribution from me this time, since I next week will show how I made my own wadding and sealing papers for CAM870 shells: