How big should a transfer port be...?

[NickG]

On the tx it's the position of the front face of the cocking shoe slot, It can be made so that there is no gap once the tube is up against the barrel (as it is once the piston is moving)the clearance is then behind the shoe. When you think about the breech set up as an o ring groove once the breech is closed it makes sense for there to be no gap.

[hmangphilly]

But isn't it the clearance ( the loose shoe ) that causes most of the slack?

Probably not an issue on many guns as friction from tight piston seal is usually enough to move the comp tube closed as soon as the piston starts moving .

[Barryg]

Probably not an issue on many guns as friction from tight piston seal is usually enough to move the comp tube closed as soon as the piston starts moving .

Yes that is my point except you don't need a tight seal lockup to start the process just a light pressure is best this is why there is slack in the TX setup to protect the seal and linkage as there is no need for a tight seal to start because it goes tight as soon as you pull the trigger on a sliding breech gun.

[NickG]

I know what you are saying, though I have found significant increases from having the port up flush with the barrel. The two o rings are a bad idea imo.

[hmangphilly]

I know what you are saying, though I have found significant increases from having the port up flush with the barrel. The two o rings are a bad idea imo.

Yeah .
But you're not running tight seals .

You renegade

[NickG]

Renegade! I like that , good point ,though it works on lip sealed guns too😀.