GPR Vent Liner length

[Gonetocamp]

I recently measured the length of four vent liners for a GPR .50 cal.: two Lyman and two RMC. I came up with four different lengths. Has anyone ever looked into the barrel thickness of the .50 cal. GPR at the touchhole?

 

[Tom Compton]

GPR has a straight barrel ( no swamp or taper) so barrel wall is the same at muzzle and touch hole. Use calipers then measure from bottom of a groove to outside flat. Make the liner a few thousandths shorter.

 

[Semisane]

The touch holes on Lyman flintlocks enter the chambered breech. Caliber and barrel wall thickness have nothing to do with the length of the touch hole channel.

 

[Tom Compton]

You are right. Sorry I forgot about the GPRs having a chambered breech and one of my flinters has one. :idunno: Oh well, senior moment I guess.

In the case of chambered breeches, does the length of a liner make any difference?
TC

 

[Semisane]

In the case of chambered breeches, does the length of a liner make any difference?

Not that I can see. The only possible problem would be if the liner were so long that it extended into the chamber. I know of no liner that long. A liner being shorter than the channel is not an issue.

 

[Gonetocamp]

Thanks Semisane and 40Flint.

 

[nkbj]

To measure the hole length it's easy to put a sharp 90 degree bend in a piece of wire to make a gauge.
Hook the bend down in there on the backside of the hole, mark the wire at the flat on the barrel, pull it out and see what it measures.