Well, to answer my own question, I chronographed two different Black MZ loads this morning behind 256g RNFP bullets from Montana Bullet Works. One load was from the 1.9cc dipper, the volume equivalent of 28g FFg or 30g FFFg. The second load was with the 2.2cc dipper and is the volume equivalent of 30g FFg or 35g FFFg. With this last one I was hoping to get the same performance I got 25 years ago shooting 35g-36g of FFFG behind a 255g bullet.
The 1.9cc load was pleasant to shoot but a bit disappointing in performance. From my 7.5" USFA I got an average of 842 fps. From a 5.5" USFA I got 749 fps for an average. And finally my 3" Sheriff's Model delivered 659 fps for 5 shots.
I was more hopeful with the 2.2cc loads and almost got it right. The 7.5" barrel averaged 916 fps, very close to what I used to get with 35g of FFFg. The 5.5" barrel was disappointing with only a 831 fps average. The 3" managed to break 700 but not by much with a 711 fps average.
One thing obvious with all the testing I did was the wide extreme spread I was getting. Over 50 fps with every load in every gun and the disappointing 5.5" test with the 2.2cc load had an extreme spread of 85 fps. This indicates to me my dipping technique needs some improvement, or I need to find a more accurate way to dispense Black MZ. Any suggestions from you all would be greatly appreciated.
Dave