IMR 4955 was used for the final test, IMR 4451 for the first.

Powder data for 4955 was derived from the 1997 Hodgdon guide, stating H4831 with 235 grain bullets, 86 grains maximum for 2665 fps.

H4831 is meant to be replaced by IMR 4955, but I know from previous experience with the powder that 4955 is hotter to the extent that when used equivalently, starting loads using 4955 approach the max velocity of max loads of H4831.

I chose to start at 70 grains, using half a grain of dacron.

Included for reference is the data from the first test using IMR 4451.

Bullet	Powder	Charge Grains	Velocity fps
245 grain lead, paper patch	IMR 4955	70	2440 average
245 grain lead, paper patch	IMR 4955	72	2530 average
245 grain lead, paper patch	IMR 4955	74	2565
245 grain lead, paper patch	IMR 4451	64	2152
245 grain lead, paper patch	IMR 4451	66	2264
245 grain lead, paper patch	IMR 4451	68	2312
245 grain lead, paper patch	IMR 4451	70	2366

Target distance 25 meters. Two bottom shots with lower charge. One flier top from the 72 grain load.

The first few shots were with 70 grains of powder, and were the two bottom outliers. From 72 to 74 grains the group shrank, and required accuracy was achieved.

There is no significant leading in the barrel, verified with a bore scope.

After shooting, before cleaning

After cleaning