question/idea about semiauto bolt

[blckwlfny]

I am posting this here because even though my motivation is to use my gun for blanks, this modification should make the gun work smoother overall.


In my continuing quest to make my SA 42 work smoother. Because I am primarily a reenactor, I have encountered pretty much EVERY problem getting my gun to work on blanks; because I can NOT afford to blow 600+ rounds at $.40 apiece, I must make my gun work on the cheaper (and weaker) blanks
One of the problems has been the loss of recoil power as the hammer skips alone the uneven surface of the bottom of the bolt. I have come up with an idea. The bolt modification usually consists of a single flat plate ground on the surface of the bolt to replace the lugs of the original. This still means that the hammer will skip up and down as the ends of the plate pass over it. Gordie K added a second plate but this also adds to the mass of the bolt. can anyone see a disadvantage to milling a flat surface (not much... 0.055" depth from the collar at the neck by the bolt head) straight back along the shaft of the bolt to make a consistent, even surface for the hammer to travel on. this should still give a wall thickness of 0.100"

...Thoughts...?

[anjongni]

H blckwfny, I'm no expert but I read on this board that it might be legal to build a f/a blank gun, "The worlds most expensive noisemaker". If that's indeed true in NY, and you're going to "exclusively" fire blanks, you could follow the NFA guidelines (available at John's German Manuals site) by thoroughly welding offensive items shut and returning your gun to the f/a fire control system, which might offer less friction through elimination of the hammer. If I'm not right on this please feel free to castigate me!...Phil

[blckwlfny]

I never looked into the possibility,my receiver is already registered by a n established manufacturer so for me its a moot point
Thanks tho.
Any other takers oon the bolt ques?

[fritsch]

It might weaken and you you might get some cracking eventually. The key word is might. It is cast, but I don't know exactly what kind of steel it is. Frankly, from a scientific perspective, I don't have a clue if that would lead to faliure or not (I'm sorry, I know that doesn't help much). I don't even weld a plate along the underside of mine. I just shape it to gentle contours and I haven't had any problems with hammer drag. However that's not to say my gun wouln't work better if I made it perfectly flat. Another quick thing to keep in mind is resetting the hammer. If you take too much off the bottom of the bolt, it might not push the hammer down far enough to reset.

My gun wouldn't work on plastic either and I tried a lot of combinations of parts. Then I made a BFA based off a Guiette BFA and it runs like a top now. It might be worth a shot.

[Blanksguy]

I know that I'll get several replies that this doesn't work.....but it does.

The 2-pcs. Blank-Barrel-Assembly (up-dated from the WWII German design) is the way to go.
Just look at the operational standpoints :
............by "volume" of space where pressure from the Blank has to build up enought pressure to operate the system, the 2-pcs. Blank-Barrel-Assembly only needs to build pressure in the barrel's-bore (it is restricted inside the muzzle)....and not the area of the Booster-Cup/"Nozzle".
.............by the weight that is required to be moved to operate the MG42/SA42.........the 2-pcs. Blank-Barrel-Assembly only requires the movement of the smaller weight of the short "piston-section w/Barrel-Extension.........it does not require pressure to overcome the weight of the entire barrel-assembly of a live barrel.
............"AND" you can remove the Booster-Cup/:Nozzle for even more noise out the front because it is not required with the 2-pcs. Blank-Barrel-Assembly.

Both the MG42 and SA42 require movement of the weight of their respective bolt-assemblies (this doesn't change unless you remove weight/"lighten" the weight of these parts for "Blank-Firing-Only".

You can play with your recoil-spring........but only so much can be removed before it will not strip the next cartridge from the belt, load the chamber, and fire the next round.
I don't believe that you can remove the bolt-rollers as they act upon the cocking of the firing-pin in the SA42.....and moving the firing-pin-holder in the MG42.

The only "down-side" to the 2-pcs. Blank-Barrel-Assembly is costs..........it either requires 2-live MG42 barrels to make it...."or", it requires the time ($$$) of a good machinest to make a threaded "Piston" for the Barrel-Extension. After cutting up so many old 8x57mm MG42 and MG34 Barrels.......we went to making the shorter piston-section on this last run just to save some barrels.
I currenntly have three 2-pcs. Blank-Barrel-Assemblies for the MG42/SA42 left/for-sale......and one 2-pcs. Blank-Barrel-Assembly for the MG34/SA34 that comes with the "L"-Shaped feed-tray-spacer.

Regards, RichardS in Bay City, MI.
US Army, Retired
Blanksguy2001@charter.net

[Blanksguy]

fritsch,
Please post photo(s) of the Blank-Adaptor that you made off of the Guiette-Manufacturing design.

Questions I would ask when you post that are:
1: Does it vent noise and flash out the front (flash-hider) and sides (Booster-Cup/"Nozzle-vents") like a firing MG42 (?)....or only out the front through the flash-hider (?).

2: Does it now work with the weaker German plastic-blanks or did I mis-read your post (?).....and if so, what other modifications did you make to your SA42 (?) (NOTE: Photos may help more here as blckwlfny may benifit from the photos as well as others for the modifications.).

3: What BFA Hole-Size/Restriction are you currently using for the German plastic-blanks (?).

Regards, RichardS in MI.
US Army, Retired
Blanksguy2001@charter.net

[fritsch]

1. Neither. I finally got it to work if it didn't vent any gas out the front through the flash hider.
2. It does work with the plastic blanks now.
3. No hole in the BFA. You can obviously see the problem there. The cases are all crushed from over gassing and there's no flash out the muzzle. The leader of my unit (5th Wiking) runs a 2 piece barrel set up and it finally pushed me to make one for myself. I got it done last night, but the 3 year old was already asleep. so I never got to test it. I'll let you know when I do. Here's a picture of it, btw. I would've made it like yours had I checked this thread before I made it. Oh well, I can cut the grooves deeper if it doesn't work this way.

[fritsch]

O MUH GERD!!! Night and day. I tested the 2 piece barrel with a 1/8" hole in the muzzle restricting screw and it worked like a charm. I left the booster out and got the big star flash out of plastic blanks.

[42rocker]

Winner Winner
I think that you might have found a winning setup. Way to go. Enjoy

Later 42rocker