My experience with RL 26 and 150 g. bullets in a bone stock Kimber Montana (24 inch barrel) is a little puzzling.

All were shot in PPU brass, WLR primers and the same lot of RL 26. Hazy to cloudy skies, temps in the 40-50 degree range, ProChrono chronograph. No missed shots by the chronograph in the testing.

Last fall with the 150 g. Hornady bullet; started at 57 grains of RL 26 working up in 0.5 grain increments with two shots at each increment:
Charge Average Velocity in fps.

57.0 g. = 2886
57.5 g. = 2899
58.0 g. = 2921
58.5 g. = 2953
59.0 g. = 2993
59.5 g. = 2973 (not a typo)
60.0 g. = 2962 (also not a typo)

Then a total of 7 shots with the 60.0 g. load of RL 26 were chronographed in two different sessions a month apart. The average of them was 3044 fps.

This spring I repeated the same series only this time used the Nosler 150 g. partition bullet and started at 58 grains of RL 26.

Charge Average Velocity in fps.

58.0 g. = 3034
58.5 g. = 3058
59.0 g. = 3078
59.5 g. = 3123
60.0 g. = 3133

At the 59.5 g. and 60.0 g. pair one primer at each step had what appeared to be a slight primer leak, just a very small amount of black on the edge of a primer. The primer pockets on these cases after depriming appeared to be normal and new primers seated normally.

So I dropped the charge to 57.5 grains and a five shot average was 2945 fps. A week later shot another 5 shot test with 58.0 g. of RL26 and averaged 2973 fps. On the same day also fired two more with 57.5 g. of RL 26 and got 2963 fps for the two shots.

In other rifles I have been able to switch back and forth between Hornady and Partitions of the same weight and get very similar velocities and consistent performance.

John Barsness reports that Partitions often give higher pressures than cup-and-core bullets. For this rifle and bullet combination his observation is correct, even though it was out side of my previous - and admittedly limited - experience.

My results appear to vary from session to session even using what I consider to be identical loads. Some variation from shot to shot is typical but several shot averages show more difference from one session to another than experienced with other rifles.

Accuracy in my rifle is good, I've shot more than one 3 shot group at 100 yds that are under 1 inch. All shots (including some mild loads with 130 g. bullets) have flattened primers and the cases do not want to rechamber in the rifle without being resized. This is true of the PPU brass and WW brass I have tested. A fired case measured at the shoulder was 0.441". This is S.A.A.M.I. value given in my Nosler #6 Manual. I assume my Kimber has a minimum specification chamber. Consequently, I full-length resize cases for this rifle. After FL resizing the cases rechamber with just slight resistance

I will do more shooting but expect loads with the Partition bullet to be a couple of grains or so less than loads for other bullets.

A different 270 with a 23.6 inch barrel doing the same series with the 150 g. Partition bullet gave a two shot average of 3010 fps with WW brass, WLR primers and 60 g. of RL 26.

"It is wise, though, to remember above all else: rifle, caliber, scope, and even bullets notwithstanding, the most important feature of successful big game hunting is to put that bullet in the correct place, the first time!" John Jobson