I found this
I just got the Hogdon Basic reloaders Manual in the mail....
for 777 in Big Bold Letters
WARNING: NO COMPRESSION SHOULD BE USED WITH Triple Seven
All powder charges are measured by VOLUME
you can use one card wad filler of .030 between the base of the bullet and the powder charge.
It does list a loading for a 500g bullet #457125 at 55gr of 777 and a 845g LFP bullet at 60gr45-70 Govt. 405 Gr. Cast LFP Triple Seven FFG 60.0 Gr. 1260 -
45-70 485 Gr. Cast LFP Triple Seven FFG 60.0 Gr. 1161 -
And this
Here's some test results with H777 60gr and the DD/PRS 400gr (actual in the 385gr range) out of a H&R BC
All 50yds through the Chrono:
Average Velocity ... Average Group
1361fps ...................0.856" (1:20 ratio - 0.030 card wad) - Crimped
1409 ...................... 0.215 (1:30 ratio - 0.030 card wad) - Crimped
1361 ...................... 0.993 (1:20 ratio - No Card) - Crimped
1421 ...................... 1.522
1410 ...................... 1.230