Firearms Design Resources

What is the English name of the milling cutter that is used to make the locking lugs of the bolt head? Also, do I understand correctly that interrupted threads are basically just like any other threads, expect that a few sections of it were milled off (with the kind of milling cutter I'm looking for)?

Attached: Bren_barrel.jpg (1200x1200, 64.1K)

Lathe?
Also yeah, interrupted threads are just threats that are interrupted by non-threaded sections.

When making a staggered magazine that narrows to a single feed position, be sure to have the magazine interior narrow enough that a space exists between each cartridge and the one directly above it. Sten mags had a lot of reliability issues until wires were added to narrow the inside. This reduced capacity but made them run as smooth as warm butter.

Checking out orions-hammer.com/blowback/ and I ran his equation to test different calibers. I got answers that seemed way out of spec so I used his equation (bolt mass in pounds = 1.09x10^-5 * bullet mass in grains * bullet velocity in fps * (diameter of bolt face / diameter of bullet base)^2) on some of the calibers he recorded to see if the error was in my data, and his equation doesn't work. I tested 9x19 and 7.62x25 Tokarev and got 1.186 and 0.856 respectively as bolt weights. These do not corroborate with his answers of 1.7 for 9x19 or 2.0 for the Tokarev round. Am I calculating this incorrectly somehow, or his math wrong?
for reference my equations are 1.09x10^-5*87*1390(.312/.387)^2 for the tokarev and 1.09x10^-5*88*1500(.355/.391)^2 for 9x19

Did you forget your recoil spring

There wasn't a variable specified, but I guess the constant spring pressure would be another variable to consider. Thanks for the angle, Japanon

Switch the diameter of bolt face and diameter of bullet base. I get 1.745 lb for 9x19 and 2.028 for 7.62x25. In the spreadsheet he also used 0.0000108 instead of 0.0000109 for some reason; 0.0000109 is more accurate.

Thank you! I want to start designing guns but I want to do it properly.

I've found an other location of Chinn's book:
milsurps.com/content.php?r=347-The-Machine-Gun-(by-George-M.-Chinn
Considering that it's there, other good stuff too might be on that side.

Does anyone know of a pistol design that has a fixed barrel a locked breach and uses the slide recoling as a bolt carrier. And would such a thing be possible