Blowback Bolt Weight

Advise

The best advise for designing a safe and secure bolt is to look what professional companies have designed.

Many of the formulas that circulate on the web are not quite correct.

It is also a common flaw in DIY guns to have, sometimes vastly, underweight bolts. A bolt too light is not only dangerous because it might open the chamber when there's still high pressure inside, but it also increases wear because the bolt moves back too fast.

For 9x19, a common bolt blowback mass is around 650g. This includes the bolt handle and attachments to the bolt that are part of the moving mass, i.e. the firing pin and the extractor.

For .22LR, a common blowback mass is 200-220g.