223 improved fire forming issues
Recently, I had Shilen re-barrel my Remington 223V to 223 improved using their select match grade blank with a 1 in 9 twist, varmint contour. Having never had an improved or wildcat cartridge I am looking forward to working up loads for a prairie dog hunt next spring. However, after reading various articles and forum comments about the fire forming procedure, I am having case loss problems with fire forming cases. I have used 3 loads as follows: New LC brass, Rem 6 1/2 primers, 25 grains H335 behind Nosler BT 55 grain with a COL of 2.260. I then fired loads used in my Stag Arms HB which is WW cases, Remington 7 1/2, Varget 25.3 grains, Sierra HPBT 69 grain bullet with a COL of 2.260. I also fired Winchester factory 55 grain ball ammo. 28 of the 90 cases show signs of incipient case separation after fire forming. Is this about normal case loss while fire forming? I spoke with a Shilen rep who suggested dropping down to 23 grains of H335 and seating the bullets out to touch the lands. I haven't tried this as yet. I would appreciate any suggestions or comments regarding this issue. Thanks in advance.