Originally Posted by
Gm54-120
...............................Is there enough case length left to make them a tad shorter and add a bit more steel to the plug.....maybe 1/4". The powder shouldn't be much further away but "flash channel/case volume" should be reduced but also add a bit more "meat" to the plug above the vent. It could probably be tested with a single thicker white nylon washer in the case pocket for a couple of shots just to test the theory.
Just out of curiosity, can you fill the powder pocket with BH209 and weigh the amount it takes to fill it or get a rough volumetric equivalent. And is that the standard Savage type OD vent or a smaller OD one you made?......................
The case can easily be made shorter. However if one is going to be able to use a case trimmer to establish the finish length of the case, it cannot. Reason; the added length of the case is necessary to accommodate the pilot of the case trimmer. These brass i finished to length by using the lathe. I kinda had hoped that i could do this in the future by using a standard case trimmer.
The powder pocket holds about 5 1/2 g volume of BH209. The vent liner head, has been turned down to 5/16" from the standard 3/8". I started doing this last winter, when i noticed instantaneous ignition in sub-zero temperatures whilst using a modified QRBP, that had a 5/16" vent liner installed. This i did because i was trying to understand why just adding a powder pocket to a bad breech plug makes it good to work with BH209.
The primers in them 223 brass show zero sign of pressure. Totally unlike what this STS shotgun primer shows with the exact same load.
The shotgun primer shows quite a lot of flow into the space in the bushing around the firing pin, and the slot in the bushing for a screwdriver. It could be the huge 'flame channel' makes this happen, or is it the fact that the 223 case is what establishes the head space when in use, not the rifle primer. When the shotgun primer is used for ignition, the primer itself is what establishes the head space.