RL22 up to approx 76 grains. I also use H4831, but my load is not as hot as Dale's (yet there is more case capacity in a rem case). I use up to 73.2 grains H4831 in my tight chambered custom 300WM with the 180 accubond.

I like Winchester's WMR in my .300 Win. mag. I use 74.0 gr. with WLR primer in Winchester brass. I get 1.25" in a Ruger #1 and 1.0" in a Mod. 70. Both rifles have 26" barrels; velocity is 3050 FPS. Pressures seem mild. I didn't see any reason to try for more. The big drawback is Winchester discontinued the powder. Supposedly, H-450 is just a different lot of the same powder, but that disappeared at the same time as well. Grafs supposedly had some for about $50 for an 8 pound cannister, but I don't know if there is any left.
I've never found the reason either powder was dropped, but probably another bean counter attack.
Paul B.

My .300 Win mag shoots the 180 gr. partitions quite well with a few different powders: IMR-4350; IMR-4831; H-4831; and IMR-7828. There are other powders I expect would do as well or maybe better, but I don't have as much experience with them yet. My rifle isn't very fussy regarding the bullet, and I usually load H-4831 on the warm but safe side.

I been loading 180gr Ballistic Tips with 80gr of H1000., 74gr of H4831 with 180gr SST and 75gr of RL22 with Remington 180gr corelocks all loads stay 1" at a hundred yards.

I have two good loads that have done well for me in rifles that i have shot alot.

75.0 grains or RELOADER22
200 grain nosler partition
CCI250 primer
and win cases crono velocity from rem 700 24" barrel was 2892 fps average this load will leave vapor trail.no xtra presure .

and

190 grain hornady boattail
77.0 grains of IMR 7828
CCI250 primer
win cases crono velocity was 2975 fps from a model 70 with a 26" barrel this load seemed to kick a bit less than the one listed above.Winchester stocks seem to fit me better and I think that had something to do with recoil.

for your reference they shot damn near the same up to about 400 yards.
both under 1 inch with stock and trigger work both you can do yourself.

The big overbore MAGs (including 300 WM) like slow buring powders. I use 83 grs. of Re25 behind a 180 NBT (~3250 fps with a 300 WM 26" barrel and ~65,000 psi). Other good powders would be Retumbo (up ~88 grs) or MRP-2 (~85 grs), both of which should give about the same performance and accuracy (I've put 3 shot groups within .25" before with the Re25 load, which also is a flat-shooting, super big game getter). I'm going to try ADI-AR2218 (aka., H50BMG), which is supposed to get 3300 fps with ~65,000 psi.

ackley improved user those are impressive numbers. Do you experiment with the .30-06 improved? I was wonering how much of an advantage it has over the orininal in reality.
Any experiance with the .270 Gibbs without the front ignition?

I have two '06 AIs (both 26" barrels), and I've experimented extensively with both. The best loads I've come across are ~67 (-/+ 1) grs. of R22 in 165 NBT (~3200 fps and ~65,000 psi) and ~70 (-/+) grs. of R25 in 180 NBT (~3100 fps and ~65,000 psi). Obviously, if you want to try these compressed loads, start below and work up, stopping when you get pressure signs.

I have two 280 AIs and one 25-06 AI, but no 270 AI. The 280 AI is one of Ackleys better efforts, but it's very similar to the '06 AI. Actually, I recommend the '06 AI over the 280 AI, because of the greater bullet selection in .308 caliber.

Ackley improved thanks for the info Ill keep my eye out for the 06' version.