I have used the Retumbo behind the 100 gr Barnes TSX in two different Weatherby rifles with charges from 77 to 81 grains, found best accuracy at around 78 grains and 3,580 to 3,610 fps, with Norma brass, Fed 215GM.
115 gr Barnes TSX
69 grs Reloader 22
Norma Brass
Fed 215GM
Velocity - 3430
I think the Retumbo is a bit slow burning for the 100gr. bullets and never tried it behind the 115 grainers.
In regards to the 100 grain pills in the .257 Roy I have found best accuracy is at the 3,600 fps range in both rifles. I have cranked them up to 3,700 and accuracy is not as good.
I have never tried the Accubond but did do some experimenting with the 115gr. Ballistic Tip but never could get velocity or accuracy I was pleased with.
