Sharps gas check plate!

[Cyknife]

I'm pondering the actual mechanics of the gas check plate. I suspect the gas check plate is forced shut under pressure in s similar manner as a dump valve; equal pressure on both sides of a valve diaphragm....bleed off pressure on one side and wham, the dump valve opens. In the instance of the gas check plate the differential between the check plate and the powder chamber is surface area over length. The gas check plate "chamber" has a larger diameter than the chamber and has the ability to move...under wham pressure it does move thus sealing the breech.

I have a pedersoli sharps with the latest o-ring version of gas check plate and an IAB sharps that I just did an o-ring job on. The IAB has a bigger diameter check plate volume. I think it also has a chamber sleeve. It doesn't move. Anyone know if IAB circa 1994 used both sleeve and plate?

It's been said the pedersoli does not seal well. The "chamber" of pedersoli's check plate is smaller in diameter than the powder chamber. May be the reason it doesn't work well.

This is speculation on my part, anybody have any thoughts on this subject?

 

[kh54]

Both the theoretical and actual function of the original Sharps gas check plate design have been a mystery to me.

My first Sharps reproduction was an IAB 1859 “sporting” Sharps. (It had no sleeve in the chamber.) I bought it about four years ago. It jammed up due to fouling on the third round I shot through it. I thoroughly cleaned it and took it back to the range but this time I swabbed the bore after every shot. I think I still got up to only seven or eight rounds before it jammed. I then called Charlie Hahn to see if he thought it was even worth spending the money on his o-ring retrofit. He did, so I had him make the modification. Afterward I could shoot consistently and accuracy up to about two dozen rounds before I had to stop and clean a little.

I sold the IAB after I found an unmodified Garrett Sharps. It actually works as it’s supposed to, at least for 10 or 12 rounds. After that I need to give it a little moose milk after every two or three rounds to keep shooting. But I don’t mind - I like the authenticity

 

[Cyknife]

I aquired my IAB recently and found that it had a warped gas check plate and the "sleeve" face was not square. So I took a file to the breech face, trued it up and honed the gas check flat on a granite plate. I also ground the back of the plate down by .030 to accomodate the o-ring. This basically sealed it up enough to fire with out leakage. I have yet to get it to a range for an extened session to see if it will go for any lenght of time without fouling.