Gunboards Forums banner

1 - 4 of 4 Posts

·
Super Moderator
Joined
·
11,691 Posts
Discussion Starter #1 (Edited)
As I promised, here are some scans from a Russian military textbook "Basics of Small Arms Design" for the Soviet military academies. This particular chapter deals with cases, forces in dry & lubricated conditions; headspace & extraction force; forces on the bolt, etc.

I apologize for the foreign text and I would appreciate if someone posts similar theory & formulas in English. Here is a brief summary:

  1. Excessive headspace leads to excessive extraction forces (sticky bolt).
  2. The force on the bolt face is not affected by the presence or lack of lubricant on the case. See the formula at the bottom of page 191.
  3. Lubrication of case only affects the extraction forces. It eliminates local over stress and the related case ruptures. See Graph 109 at the bottom of page 189

There were some statements as to how a lubricated case will cause excessive thrust on the bolt by not gripping the walls of the chamber. The notion is probably derived from an analogy with holding a wet soap, but is really not applicable to the case behavior. At least this is what the graphs and the formulas in the Russian textbook say:
 

·
Registered
Joined
·
320 Posts
... Here is a brief summary:

  1. Excessive headspace leads to excessive extraction forces (sticky bolt).
  2. The force on the bolt face is not affected by the presence or lack of lubricant on the case. See the formula at the bottom of page 191.
  3. Lubrication of case only affects the extraction forces. It eliminates local over stress and the related case ruptures. See Graph 109 at the bottom of page 189

...
Interesting! Thanks for the information, Nick.

Kim
 
1 - 4 of 4 Posts
Top