O-ring / Breech Block Upgrade
Sharps Type Externally Primed Rifles and Carbines


Sharps rifles and carbines with the standard type moving gas check plate and loose fit to the barrel end usually result in gas leakage, breech freeze up and over time metal erosion.  This causes non-uniform performance and potentially damaging conditions due to the leakage of high-pressure gases.


O-Ring Mod
Upgrade Options:

Solid Block Conversion with captive o-ring:   This is considered the full job and changes the configuration of the breechblock.  The gas check plate is fixed permanently to the block and the fire path is renewed.   This provides the best option for better shooting.

Sealed Block:   This has limited improvement, but does not require the modification to the block.  The fire path is not renewed and the gas check can be removed about every 400 to 500 rounds for reseal and fit.  The owner can do this; instruction is provided.

The captive o-ring is included in both modifications.  The breech is machined to accept the stepped short sleeve and o-ring.  The forward section of the sleeve is fixed permanently into the barrel.  O-ring part numbers and grease are provided to the customer.  Assembly instruction is provided.


It is important to understand that the sealing surfaces require maintenance and will wear over time regardless of which option you select.   I do specify the o-rings and grease that I make available direct from the industrial supply house I use.  I can supply these items if requested. These parts should not be substituted, as they have been selected as a result of extensive development and testing.

                          Soft 0-ring, round --  P/N 2418T123,
Extreme High Pressure Grease --  P/N 1392K31 both from mcmaster.com

I provide help via the phone or click here to contact me.    I try to be available to answer any questions you may have.

Charlie Hahn