I have been working up loads for my Uberti 76 in 45-60 for over a year now and thought I would share some of what I have learned. I have a Marbles tang sight and use a varity of front sights. The bullet I have been using is the RCBS 300 GC. The nice folks at Mt Baldy cast this bullet with 1:20 alloy and SPG lube for me and it weights 321 gr. I bought my cases from Buffalo Arms because my 76 will not close on cases with a rim thickness greater than .062 in. I trim the cases to 1.870 so that the OAL with the bullet is 1.292 which feeds very smoothly through the action. I sometimes use Puff-Lon filler in loads as noted. I never use wads with smokeless powder.
I have tried several different powders and primers but here are the three best so far.
30.0 gr H4198 no filler, accuracy superior, vel 1450 fps, 50 yards.
Although the accuracy is great I will probably reduce this load to 28.0 gr and try to get the vel to 1350 fps.
Same load at 100 yards.
60.0 gr Swiss 1.5 (30 in drop tube and .070 compressed), .030 card wad, .125 lubed felt wad
This load is very accurate at 1290 fps and shows promise for shooting a 40 shot match. 50 yards
Another load was 26.5 gr 5744 + Puff-Lon filler to case mouth
This load gave the following results for two strings of five;
velocity 1422 1416
SD 2.7 3.4
ES 6.1 8.3
These are some of the lowest SD I have ever gotten.
The accuracy was very good but since I had run out of targets I was shooting at targets with holes already in them.
If anyone wants any additional information I will be glad to reply
Jubal