I dug up only one thread in this forum containing some data from mathman regarding this powder in the .300 Savage, figured I'd add my findings.
I no longer own a 99 in .300, and this work was done for an Interarms Mark X which would handle higher pressure rounds without issue. Like mathman I found 39 grains a good starting point and it averaged 2506fps with a 155gr Hornady A-Max. Primers looked good, had easy bolt lift and extraction. My club held a long range silhouette match today and that one doped out well for turkeys and rams.
Also tried this powder with 125gr Speer TNT varmint bullets, but the loading I'd done using H4895 with that one for my 99R was good in the bolt gun as well. Same with Reloder 7 and Sierra's 125gr Pro Hunter, Chicken and pig loads.
I've shot a number of factory rounds through both of these rifles, not at the same time so no true direct comparison here, but my chronograph saw:
Remington 150gr Core Lokt 2530fps in the 99R, shot them all up prior to building the Mark X
Federal 150gr SP 2655fps in the 99R, 2660fps in the Mark X
Winchester Power Pt 150gr 2592fps in the 99R, 2704fps in the Mark X
Hornady Superformance 150gr, bought after selling the 99R, 2695fps in the Mark X.
Have to shoot more of the Winchester ammo through the bolt gun. Just in case it repeats.
Would like to see one of the bullet companies work with this powder in the .300 to get good known, safe loads for 99s, I've also done some shooting with this and IMR 4451 in a .250 AI bolt action rifle, but a Sierra tech tells me they have no intention of working further with that cartridge. My rifle follows very closely with the data they published for the cartridge.
I'm happy with H4895 and Reloder 15 in the .300, was curious what the newer powder might provide. Limited trial with the RL15 round that worked so well in my 99R didn't look so promising in the bolt but I've got some leeway with seating depth as that one's only 2.56" oal with throat room in the bolt. That, and a little more or less powder, should get it right.
For reference, here's the prior thread
https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/11963946/1
