Regarding FFFg vs. FFg: Both were used "in the day," in shotguns and still are today. The finer grade produces a somewhat higher peak pressure, all else equal.

Comparing published data for 12 ga loads shows that 3 drams of FFg produces 4500 - 4900 psi with 1 1/8 oz shot (3 sources). FFFg creates a peak of of 6900 psi BUT with a 4 dram load (I don't have a 3 dram comparison at hand, source is David Butler, former W-W engineering manager).

However, Sherman Bell also tested (recently) 3 3/4 dram FFg under 1 1/4 ozs of shot (close to the 4 drams cited above but with 1/8 oz more shot) and found a 5900 psi peak -- 1000 psi below the FFFg 4 dram load with 1/8 oz less shot.

Last edited by Fred; 02/01/07 12:57 PM.
Fred