I was able to do a modified 'Audette ladder test' the other day with Retumbo in a 7mm Remington Ultra Mag. The powder itself is somewhat finer than many boomer powders, so it should meter fairly well. It did take 1 1/2 months to arrive on backorder, but that's life.
Wind: 10-20 from 5:00 to shooter
Humidity: 98% with light rain
Action: Remington LA
Barrel: Kreiger 30" 1:9" twist heavy Palma taper, no muzzle brake
Stock: McMillain Prone w/3 way buttplate
Trigger: Jewell set @ 1 lb.
Scope: Nightforce 12-42x56mm,set on 40X
Bases: Champion's Choice 30MOA
Rings: Badger Ordnance 30mm
Brass: Remington 300RUM necked down to 7mm & fireformed, prepped but unweighed
Bullets: Cauterucio 176gr VLDs seated .005" into the lands
86.5 Starting load - fouler
90.5 Stiff recoil, primer cratered, minor stamping
91.0 Stiff recoil, primer flattened & badly cratered, heavy stamping & bolt lift - TIME TO QUIT & BACK DOWN!!!
All shooting was done at 200 yards. The total size of the group (excluding the fouler was 2.049." The three rounds at 87.0, 87.5, & 88.0 grouped at .570." The three from 89.0, 89.5, & 90.0 grouped at .984."
Recoil & muzzle blast was noticably heavier than max loads of 5010 that I'd used last year with good results. Obviously, the next phase of testing will involve groups at longer distances with powder charges of 87.5gr & 89.5gr, in addition to a chronograph to check velocity.
All in all, inconclusive, but promising... This rifle is primarlty used in conventional LR competition, but will occasionally be used in LR coyote & deer plinking. The 5010 pulldown standard goes out at 3,360 & ES & SDs in the low teens. Average 500 yards groups for it with 5010 were @ 3.25" last year. At $4/lb, the 5010 is tough to beat for that performance, as opposed to $18/lb for Retumbo.
Your thoughts & comments???