www.MG42.us

16 1/4" bbl semi auto 42 carbine, should begin test firing this week. Just have rails and final fitting to go



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How are you going to deal with the barrel bearing surfaces at the muzzel end?

well if the barrel was thick enough at the 16 inch mark as the end of the normal barrel, you could turn the shape down after you cut to length. (reshape barrel bearing tip on 16 inch barrel.) you might want to drill out the muzzle cone to relieve some excess pressure. that thing might drive right back through recup and destroy it! john

by the way beachbum, LOOKS NICE!!!

There wasnt quite enough material to turn the rings on the end of the bbl so I chucked it in the lathe and turned the last inch and threaded it, then turned a new piece that replicates the end of the original bbl, screwed it in place .

Any thoughts on what size I might need to ream the booster cup to?

panaceabeachbum,

Just an opinion(s)/thoughts at this time from years of dealing with the Blank-Adapting of both MG42s and MG34s......
1: Set the gun up using the shorter "Barrel-Bearing" which is about 1.865" long......and re-machine the end of the barrel so that it not only has the same shape and contours as the original....but that the threaded-on adaptor (you may want to consider welding?) will not pop-off or "hammer" itself off or to one side allowing the projectiles to hit your Booster-Cup/"Nozzle".

2: When setting it up....prior to turning/positioning your adaptor on the muzzle end of the barrel.....determine where this should be by measuring/lay-out of what you want to do on paper........the measurement of the Barrel-Bearing's protrusion out of the front of my CRA FA MG42 receiver is .485" with the shorter 1.865" Barrel-Bearing.........and at .590" when I use the longer 1.970" length Barrel-Bearing.

"IMPORTANT".....The length of the barrel-bearing determines when the "excess" pressure is "dumped" out the side-hole of the Flash-Hider (IE: "Timed" pressure-release). This "timed-release" is used to allow only enough force to move the Bolt-Assembly to the rear and operate the rest of the moving parts such as the feed mechanism...........having too much pressure left over (if not required to operate your gun) fron a longer barrel-bear will allow the bolt to slam reward during operation....and accelerate wear/breakage of parts.

3: As your barrel is also lighter in weight now.......I would also start with a Booster-Cup/"Nozzle" that has the largest forward hole-size that you can find.......(IE: 14mm ?).....you can always locate smaller hole-sized Booster-Cups/Nozzles.......but too much pressure at the critical time when the bolt is unlocking may allow the bolt to slam-back into the recoiling parts. ALWAYS make changes to the booster-cups/Nozzles first...starting with the largest working down to the smallest......if it doesn't work by then, "THEN" change the length of the Barrel-Beraing to the loger bearing and back to the largest booster-cup/nozzle hole-size.

REMEMBER....always start with the shortest length Barrel-Bearing....and the largest hole-size for your Booster-Cup/Nozzle......you can always go back and change them later if the need is required to get more recoil/reward-force.

Other than those "suggestions"/"thoughts".......I think it looks great !!!!
Regards, RichardS.
Blanksguy2001@chartermi.net

The bbl bearing currently is sticking out .495 beyond the threads, I was considering initialy using a locking nut to position my end piece at various lengths, for dif lengths of bearing protrusion, to control the port timing . I have the cnc lathe turning out a few diff booster cups now so I can start at 14mm and work my way smaller till I get smooth operation. If I workout the proper diameter and it runs reliably I will just weld the end piece on the bbl. Should be able to test fire tommorow once all the neighborhood kids are at school. All advice welcome, dont want to tear up my new play toy.

make sure you have 911 programed on speed dial on your phone!!!!!! john

looks nice , I would try an 8mm cup with 308 ammo see if that works as a starting point

sweeeeet

hope I dont need to call 911, Im a firm beliver in string and large distances for test firing though. Machined 4 booster cups , 12.5mm - 14mm from 4130 for tommorows testing, still need to fit recoup and spend a few hours making sure I havent missed any little details. Fingers crossed.

Good luck!!! Looks cool as hell!!

Your ideal is really neat. I want one too.

finaly got a little free time today to try out the carbine, 14 mm booster just will allow gun to unlock and open enough to ram case neck into the mouth of the chamber with top cover open, 13.5 mm allows ejection with top cover open , with top cover closed its just enough to let case ram into breach face but not quite enough to eject. I have a little binding of the feed roller track on the top of rec to clean up and I believe it will eject with cover down and 13.5mm booster in place. Might need 13 mm to function with a loaded belt hanging off the side, should be able to work with it a little more this week end after I get top cover clearance issue worked out. Everything looks promising so far.

Beachbum,
Man, that looks great, an MG42(k)! I want to build an MG34S one of these days.

I say ya put a forward grip n that bad boy ala M60 E3. Hoooyah!!!

got everything moving as slick as possible in the 42sa carbine yesterday and was able to run two 50rd belts thru the gun without a single hicup, settled on the 13mm booster , runs great off the soft mount or the shoulder. The 13.5 only ran off the shoulder. This thing is just a blast. I know know if there is any practical reason to have cut it down by only 4" but it sure seems alot easier to shoot off the hip. Should get around to bead blasting and parkerizing later in the week.


I have another set of the new BRP rec halves welded up as a virgin rec for the pistol build. decided to order the bbl shroud stampings to cut down to insure that 100% of what might be construed as a receiver is virgin and US made . Im thinking 10" bbl for the pistol.

panaceabeachbum

Please post pics of your pistol. I have got to see this.

My hats off to you

sweet

panaceabeachbum wrote:hope I dont need to call 911, Im a firm beliver in string and large distances for test firing though. Machined 4 booster cups , 12.5mm - 14mm from 4130 for tommorows testing, still need to fit recoup and spend a few hours making sure I havent missed any little details. Fingers crossed.

Boy that looks cool, what type of fire control are you using?
I would consider building one using a yugo kit.