Barrel length's effect on rate of fire

[MyFirstMachineGun]

So......I was thinking that I might try to cut down a max-31 to make it more like the 31k.
1st. does anyone know how the shorter barrel would affect the rate of fire.
2nd. If anyone has done this. please post pictures, result, instructions.

thanks

 

[rybread]

I’ve done it.
1) Changes in barrel length is not necessary
2) had a metal shop I trusted (a lot) saw it right off just in front of the trunnion.

http://www.uzitalk.com/forums/showthread.php?83938-Max-31SK-amp-CF-W-super-slow-fire&highlight=

 

[MyFirstMachineGun]

I’ve done it.
1) Changes in barrel length is not necessary
2) had a metal shop I trusted (a lot) saw it right off just in front of the trunnion.

http://www.uzitalk.com/forums/showthread.php?83938-Max-31SK-amp-CF-W-super-slow-fire&highlight=

So did you chop the barrel?
Do you have a picture of your upper ?

 

[cajun 22]

A couple of pics here,

http://www.uzitalk.com/forums/showthread.php?87290-Max-31k-interest

and here,

http://www.uzitalk.com/forums/showthread.php?82404-Why-no-Max31k-for-M11-9

 

[MyFirstMachineGun]

Cool, do you guys know if the fate of fire will change if I chop the barrel

 

[rybread]

Cool, do you guys know if the fate of fire will change if I chop the barrel

It sure will, though to what degree depends on before and after length.

 

[MyFirstMachineGun]

- I would cut down the original barrel, (8 ¾) down to around 5-6 inches. Would the Rate of fire go up or down with a shorter barrel?

 

[thelastdinosaurs.com]

Usually down in open bolt guns.

 

[MyFirstMachineGun]

Sweet! thats what I was hoping for

 

[bimus]

How dose barrel length effect a blow back operated gun ?
or this the same question just reworded ?

 

[Gaujo]

- I would cut down the original barrel, (8 ¾) down to around 5-6 inches. Would the Rate of fire go up or down with a shorter barrel?

Less dwell time in the barrel means less force going backwards. Thus the 31k bolt is lighter than the 31 bolt.

 

[MyFirstMachineGun]

Less dwell time in the barrel means less force going backwards. Thus the 31k bolt is lighter than the 31 bolt.

You wouldnt happen to know how much lighter ?

 

[Vegas SMG]

Less dwell time in the barrel means less force going backwards. Thus the 31k bolt is lighter than the 31 bolt.

The 31k bolt is lighter because it’s shorter for the limited available travel. That’s because the .380 lower the MAX-31k is made for is two inches shorter than the MAX-31 for the M-11/9.

With a PACT timer, I’ve documented a 50 RPM drop in the ROF in 9mm with a one inch barrel reduction going from 6” to 5”. That was with a CF-W “A” bolt used in a Practical Solutions GG upper.

 

[Gaujo]

I should have said the 31k bolt is lighter than the 31a bolt.