When I pulled the bullet and weighed the charge in a Federal round I got 89.something.
If you use the cordite to RL 15 conversion formula (C x 1.19) 75 gr of cordite would equate to 89.25 of RL15.

Federal can load without fillers since they use a hotter primer (F216?) that's not available to us mortals. When I load with the F215 / RL15 I add 6-7 gr of polyester pillow stuffing to keep the powder against the primer.

For a 1954 WR double I worked up from 85 gr and settled on 90 gr since it regulates perfectly with Woodleigh softs. Use one grain less for solids. Velocity runs 2125 or so.

SOS