I hope someone can give me some guidance.
I have a Pedersoli RB that I have shortened 45/90 Starline brass for and after firing the brass is stretching approximately 0.012”. Not all but most.
I made a chamber cast and as best I can tell the length of the chamber is 2.129” which is the same as a Pedersoli chamber drawing I found somewhere. Also I don’t see a throat as it appears that the lands come all the way to the chamber end which has a taper (from chamber end) less than 45*. Possibly around 10+* as per Pedersoli’s drawing. I might add that what appears to be lands at the chamber very well might be the 1* or so lead angle.
The rim thickness on the Starline brass is around 0.066”. So I assumed that allowing for the .0.004” headspace due to rim thickness I’d better use 2.125” as my max chamber length. So I trimmed to 2.122” just in case it shortened some after firing. This brass had been fire formed previously and lengthened some then also.
My load is 82gr OE 2f with a 0.063” poly wad with around 0.100” compression with a 513 gr baco 441” patched to .449” bullet. BTW this load is shooting around 2 moa at 100 yds or better with a few fliers so I’m happy with that! I did not size the fire formed brass other than the slight taper crimp.
After firing most of the cases measured 2.130-134”. At this point I don’t know if I need to trim to 2.129” or trim shorter or what to stop this case stretching. Or maybe it will stop now? Also I didn’t notice any mouth curl due to the cases stretch forward. I’ve read that poly wads can cause this but I don’t know. Also this brass might have been anealed but I can’t remember due to this projects been on the back burner for a few years.
I think I’ve given all the info I have. Any help will be appreciated.
JD