SS Bisley 44 Special with 4-5/8" barrel. Cast up some 255 gr LBT WFN-PB using straight WW about 4 months back; BHN of 12-13. Now, siting for 4+ months later, the BHN is 15-20. The typical 7.5 gr load of Unique won't shoot. Need to bump the charge to 8.5 gr before groups shrink. Could it be the harder bullets are not obturating/bumping up to fill the bore, at the lower pressures, due to the harder/older BHN/bullets?
7.5 and 8 gr charges, groups running 4-5" where the 8.5 gr is between 1.25" and 2.5" for 5 shots at 25 yds.
Thanks,
Alan