Good morning Harry.
Backing in the numbers:
1. 20 ga standard nominal id is .615
2. the subject barrel walls have been honed and reduced by .0065
3. original wall thickness would have measured .028, now they are .022
Parker 20ga barrel wall thickness is usually .028 to .035, however some original thickness light Parker 20's were made in the .020 to .022 range. Those barrels were proofed with standard SAAMI proof loads and intended for standard 7/8oz 2 1/2 dre loads.
The above facts are for consideration. I know that Parker 20's with thin barrels in the .022 range are in use and I have heard no reports of burst or bulged barrels in them from standard loads. I know that some shooters use 1 oz 2 3/4 dre loads in late Rem Parkers and I would be uneasy about that in such a gun as the subject gun.
|