General blank adapting question

blckwlfny
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General blank adapting question

Postby blckwlfny » Wed Feb 04, 2015 6:40 am

Ok, Ive noticed something after this last reenactment.
I have a semi MG-13, but im not sure if that's relevant I have a 2-piece barrel in .308 that HAD been running perfectly with the same blanks (same lot#). I was tuning it before the event and I realized that the colder it is, the less the blanks work (and that it cools down within about 5 min in the cold weather) Not only do the blanks make significantly less noise in the cold, but they are failing to cycle the action. Here's the problem i had at the last event. The gun would not cycle so i restricted the orifice until it just cycled. Then about 5 shots in the gun cycled fine but without a tremendous "bang". 10 shots later, I blew the buffer and the top cover pin.
Im not looking for a solution, just a reason....or at least a confirmation that im not crazy....relatively
ideas?

Blanksguy
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Re: General blank adapting question

Postby Blanksguy » Wed Feb 04, 2015 12:49 pm

Hi John,
Saw your question and have a few answers.......this applies to almost all weapons that are "blank-adapted"......and I have to go by the "limited" information that you have provided.

1: Primers ignite slower in colder weather/"temps" as gun-powder burns slower in colder-temps...........and this is what is termed part of "interior-ballistics". This is the same reasons that you sight a dear-rifle in (for best results) in/about the same temps. that you will be hunting in..........this also applies to altitude effects "burn-rates" of powder........and the reasons why you have more bullet-drop.
When you relate those last statements into the "Blank-Adapting-world".......you see the need for different BFA Hole-Sizes/"restrictions".

2: When we set up weapons for Blank-Firing......we suggest that the users take notes of temps. vs. BFA Hole-Size vs. the Blanks used ......and then make up additional restrictors. With this I mean that if you set up during hot temps where powder in Blanks burn fast......then make up additional restrictors one size larger for even hotter weather.........but in 2-3 sizes smaller for when the temps. get colder and/or the gun gets dirty. (Note: The reverse is true if going to hotter-temps..

3: Not all Blanks are loaded the same.......and even though you have x number of US .308 Blanks.....and x number of German plastic .308 blanks....they are not loaded the same and can not be mixed on the same belt.
Also, blanks that are not stored correctly (I didn't say by you......one of the previous owners) will have mixed results.

4: If a Blank-Adapted-system.....as with live ammo.......is not fully locked at time of ignition, or fires early, then yes......you could get an out-of-battery explosion. These will usually show up as blown-unlocked top-cover.

Next questions (?).

Regards, RichardS
US Army, Retired.

42rocker
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Re: General blank adapting question

Postby 42rocker » Sat Feb 07, 2015 8:17 am

You have just received an answer from one of the top folks that know about blank firing.

Richard -- Thanks for all of the sharing that you do here...

Later 42rocker

blckwlfny
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Re: General blank adapting question

Postby blckwlfny » Mon Aug 24, 2015 5:28 pm

just figured id reply with the solution I discovered to my problem.
the mg 13's recoil spring doubles as its holder for the top cover. it turns out that my spring was in need of replacement.
did so and all is well


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