How much pressure will escape from the vent-hole depending on caliber etc.?

[derringeer]

If the caliber is small I guess the vent-hole also has to be small, in comparison with a big cannon that could use a big vent-hole. I wounder how big is too big for a vent-hole depending on the caliber and the length of the barrel? Could a gun with a short barrel, like a philadelphia derringer, use a bigger vent hole without any loss in velocity since the bullet will escape the muzzle before all powder has been combusted inside the barrel anyway?

 

[michiganmuzzy]

I think the powder youre using makes a bigger dif as far as what size hole. A good fffg black like swiss and yer probly needing only a .026- .028. I agree that a short barrel limits yer V so imho you should try to trap as much psi as you can.

 

[michiganmuzzy]

I wonder whats the smallest hole you can reliably ignite swiss fffg thru? I think .026 is the smallest ive ever seen for sale.