Blank Help, Gun won't run

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M1 Tanker
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Blank Help, Gun won't run

Post by M1 Tanker »

I can't get my semi 42 to cycle blanks and need some help.

The gun runs 7.62 and 8mm like a champ. This morning I ran about 50 rounds of live 8mm before swaping the recoil nozzle to a blank setup.

Here are the details:

AtlanticWall 8mm blanks (the packages say semi/full MG34/42 with a .140 BFA).

I tried 2 different size set screws in my recoil nozzle, .140 and .136. The will not bring the bolt...I don't think it was even unlocking the rollers. It was peeling back the crimp on a small portion of the case. They did seem really weak...especially after shooting 8mm.

I also have a recoil nozzle that someone has welded up the gas escape ports, but didn't try it.

Suggestions? Ideas? Insults? :)

I was going to try a .128 set screw next, but wanted some opinions.
Blanksguy
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Re: Blank Help, Gun won't run

Post by Blanksguy »

M1 Tanker,
You came to the right place.......but if you (or anyone) needs "Blank-Adapting" information for the MG42 or MG34.....you can e-mail me directly (and let me know that a new "thread" has been started with a Blank-Adapting question) and I will come back over. I don't visit as often right now as I am still trying to get use to the new "Board-look".

Your SA42 firing blanks......
First, let me start by saying that in the past few months, I have been helping AtlanticWallBlanks (Robb Walters) to making the same Blanks as far as loadings as I have been making since about 1988. That .140" is the BFA Hole-Size/Restriction for the G43 Rifle....and a starting point for the MG42/MG34 Weapons systems.

On the SA42 I will have to ask a couple questions first to help you sort this all out. Let me know if I an not correct on any point or part :
1: Have you read the Blank-Adapting information that I provided earlier on the Board and that should be tacked up near the top (?).

2: I understand that you are using a live barrel (w/restricted Booster-Cup/"Nozzle") instead of the 2-pcs. Blank-Barrel-Sysetem where the restriction is in the muzzle of the forward half.......correct (?).

3: I am also reading that you have tried the .140" BFA Hole-Size....and this does not fully operate your SA42 (IE: The Bolt-Assembly is not coming back far enough for the fired Blank to be ejected nor the next loaded Blank to be chambered into your SA42 (a closed bolt system).....correct (?).

4: You also state that your SA42 operates well in 8x57mm and 7.62x51mmNATO with live ammo......correct (?).

What is happening is that the pressure is not building up high enough to cause the complete barel-assembly w/bolt to be pushed back far enoygh to unlock the bolt and then push the bolt-assembly completely to the rear so that the ejector-rod can hit the buffer and kick the fired Blank out of the weapon.

At this point there are a couple things that you can do.....most of these will depend on how loud you want the weapon, and if you are open to putting the money into a 2-pcs. Blank-Barrel-System. You see, the loudest way to operate either the MG42/SA42 or the MG34/SA34 is with a 2-pcs. Blank-Barrel-Assembly.
With what you presently have you can only make the BFA Hole-Size smaller in increments of .010" at a time until it operates normally. This may be at about .1285" (#30 Drill-Size)....or .120" (#31 Drill-Size)....or .110" (#35 Drill-Size)....or even down to .0995" (#38 Drill-Size). The reasons for this is because each weapon is different due to how they were welded together, condition of parts/springs, friction, etc. ..........especially the SA-42s as they have an additional hammer/hammer-spring-pressure to override.

One thing that you can check/try is the longer Barrel-Bearing that is 1.970" long if I remember correctly as this will hold the pressure into the Booster-Cup/"Nozzle" a split-second longer. You see, when these SA42s were welded up....they come out at differnt length receivers....some won't allow the barrel-bearing to stick out as far as others. Remember, the Barrel-Bearing is made to work as a timed-release to dump the excess pressure in the Booster-Cup/"Nozzle area right as the bolt is unlocked and starts moving to the rear.
This may help some...but will never be a loud as a 2-pcs. Blank-Barrel-assembly with the same blanks.

With those same Blanks, my C&R MG42 (set up with a live-barrel and restricted booster-cup/"Nozzle" will operate at about .110" (#35 Drill-Size).....but with a 2-pcs. Blank-Barrel...it will operate at .140" BFA Hole-Size/Restriction in the muzzle. Larger hole-size equals more noise. Those some Blanks operate my C&R MG34.......but I guess I need to make up an SA42 and SA34 of my own to be able to do more "in-house" testing. ((anyone up for some welding (?)).

Last, I believe that I am starting to see a "pattern" with the difference in BFA Hole-Sizes/Restrictions between an MG42 and SA42 (if set up with the same Blank-Adapting/barrel-systems)....or about .010" smaller required for the SA42 or SA34. As we get more "feed-back" from users of this Board it will help us to better track this......soooooo please post what has been working.

.......and M1 Tanker.....let us know how things worked out and what you ended up with for your final settings.

Let me know if you have other questions that I can help you with.
Regards, RichardS in MI.
Blanksguy2001@chartermi.net
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Re: Blank Help, Gun won't run

Post by M1 Tanker »

Thank you for your reply and time. I was a little worried going down past .136, but you have calmed that fear.

1. Yep, read it a bunch :)

2. Correct, I am using a live 8mm barrel and a modified recoil nozzle. I can't find a 2 piece MG42 barrel, I've looked for almost a year....maybe I just have no luck.

3. Correct, .140 does not permit enough gas buildup to unlock the bolt.

4. My SA42 will run live 7.62 NATO and 7.92 x57 without issue. To verify I ran romanian 8mm this morning to test my 8mm setup.

I will check my barrel bearings and measure length tonight. I will also make up more set screws in the sizes suggested tonight and retest tomorrow.

Thanks for the info, I'll post results tomorrow.
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Re: Blank Help, Gun won't run

Post by Blanksguy »

Why don't you just have a local machine-shop turn one down on a lathe for you from two-used MG42 Barrel-Assemblies (?).

I posted a drawing in the MG34 Blank-Adapting Section some time ago......and they are basically the same except the "extension". Just remember to leave from .005" - .010" running-clearance for the piston-end to move in the forward half.
You could even have an additional chamber-end/extension made up for 7.62x51mmNATO Blanks.......and do a third one up for 30/06 Blanks (same case-length "star-crimped" Blank as LC is making today.

Who are you "reenacting" with (?)...what unit/impression (?).

......and if you run into any "restorable" US 75mm Pack-Howitzers, or M3A4 Hand-Carts for sale in you area (or US 75mm Pack-Howitzer Breach-Ring-Assembly)....send me an e-mail.

Regards, RichardS in MI.
Blanksguy2001@chartermi.net
Last edited by Blanksguy on Wed Jun 27, 2007 7:24 pm, edited 1 time in total.
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Re: Blank Help, Gun won't run

Post by M1 Tanker »

I may do that Richard, thank you for the suggestion. I had not read that in the MG34 section.

Yes, I re-enact. Currently we are doing 167th Volksgrenadier, the opposite of the uber elite units out there :)

The only carts and howitzers I ever see are here on Ft Hood ...and I don't think they are gonna give them up..hehe.
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Re: Blank Help, Gun won't run

Post by M1 Tanker »

Just a FYI to let ya'll know the situation with blanks and a Semi Auto 42.

I have 2 brands now: Atlantic Wall and Swansons.

I got the Swansons to run on a .086 BFA. They are loud loud loud.

The AW blanks still won't cycle at .086. It will unlock the bolt now, but only moves the bolt about 1 inch to the rear. They are significiantly weaker then the Swansons.

More testing to follow with even smaller BFAs.
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Re: Blank Help, Gun won't run

Post by Blanksguy »

M1 Tanker,
I read your posting and now really have some questions. I only have the FA MG42 and FA MG34....I have not had time to build an SA42 nor an SA34 at this time.

1: Is there that much difference between the required operating pressures in an SA42 vs. an MG42 (?) (IE: Required spring-pressure to pull the bolt to the rear and overcoming the spring-pressure of the hammer on an SA42 vs. just the recoil-spring in the MG42 (?)).

2: What length Barrel-Bearing are you using (?)...if I remember correctly.....you are still trying to use that one-pcs. live-barrel/restricted Booster-Cup/"Nozzle" method.......correct (?).

3: When you say that you are using a "modified-booster-cup"....are you trying to make a "Blank-Adapted Booster-Cup/"Nozzle" by welding up the front exit-hole on an old Booster-Cup/"Nozzle"...and then drilling/taping it for different drilled-sized allen-set=screws (?)

All of these questions will go back to the "operating-time" is slightly longer for an SA42 vs. the MG42 due to the additional spring-pressure in the hammer-spring. That split-second time that the bolt is trying to overcome the hammer-spring-pressure.......your "Blank-system" is losing "presure". This is also why you have had to lower the BFA Hole-Size for your Blanks at the front of your gun.........
When you add in the weight of a live barrel vs. the smaller weight of just the rear-section of the 2-pcs. Blank-Barrel-Assembly.....I believe that you can start to see what is happening.

With this loss of pressure (and smaller BFA Hole-Size)....will also come less noise out the front of your weapon.

Some "tricks" that you might try until you have that 2-pcs. Blank-Barrel-Assembly made is to:

1: Use the longer 1.970" Barrel-Bearing......it sticks out of the receiver a little longer than the shorter barrel-bearing and holds the pressure in the Booser-Cup/"Nozzle" for a split second longer.

2: Weld up one of the rear-slots at the rear of your Blank-Adapted Booster-Cup/"Nozzle", and then use a die-grinder to clean up the area. This will allow more pressure to remain in the Booster-Cup/"Nozzle" area and may aid in operating the system you have built. (NOTE: Only weld up one rear-slot at a time and give it a try with those "larger" BFA Hole-Sizes/Restrictions. You may have to do 1-2....or even 3 to get more pressure retained in that Booster-area to operate your system.).
This option is done on a less costly part (Booster-Cup/"Nozzle" vs. Flash-Hider.

Keep looking for someone with a good lathe....and pick up a couple of spare/shot-out MG42 Barrels.
Make sure that you have it made with a "flair" at the rear of the forward barrel-section.
Last....post more feed-back as you work on your system.
Again.....you will have less problems...and more noise with that 2-pcs. Blank-Barrel-Assembly.

Regards, RichardS in MI.
Blanksguy2001@chartermi.net
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