John,
Have you tried R16?
R
Yes, but only with 130 and 140-grain bullets, in a Mossberg Patriot rifle, which had a 22" barrel. It worked really well with the 130 Nosler E-Tip, with groups well under an inch at right around 3100 fps. With Nosler 140 AccuBonds it grouped around an inch, at a little over 3000.
Basically RL-16 is about like IMR4350 in burn-rate, but double-based and very temp-resistant, with a decoppering agent. Have had the best luck with it in moderate-capacity 6.5s like the .260 Remington and 6.5 Creedmoor.
