I am working on loading these and have some questions. Please note that I am a beginner reloader but am comfortable with it.

My load info comes from Woodleigh.
215 Fed Primer
H4350 Powder 68 to 72 grain
350 grain PP
350 grain Solid
350 grain Soft
Federal silver colored case.

I loaded 5 catridges of each at 68, 70 and 72grains

68 grains all the were moving at just under 2200

70 grains
SN 2223 avg hi 2249 lo 2204
Solid 2261 avg hi 2282 lo 2248

72
SN 2303 avg hi 2322 lo 2297
Solid 2313 avg hi 2326 lo 2302
PP 2280 avg

According to Robertson's book at 2350 there should be about 53,000 pressure (though he doesn't specify powder/primer)

All loads shot nice groups. The light loads were downright pleasant to shoot. The heaviest load did an odd thing. Of the 15 shots, two caused a slightly sticky bolt. And the cases have a strange mark about 1/2 down from the throat. It is a slight indent about 1/16" wide in a half moon. Primers look fine to my untrained eye. None of the other loads exhibited this.

Rifle Win M70 375h&h regular barrel, brake on.

1) Am I "overpressure" on the max load?
2) What is that mark? (it isn't the gas hole)
3) What is the momentum of this load at 2261 fps
4) I think the next step is to try 71 grains. Does this make sense?

Thanks,

John

I've checked with Quickload 3.3 and I would personally stop at 70 grs. since the estimations indicate an approx. pressure of 53,700 psi, while at 72 grs. you should reach 58,800 psi; that's only a guess, of course.

The dent could be caused by some sort of debris that was/is stuck in the chamber.

As for the momentum, I've never cared about it and I cannot calculate it for you.

Hope it helps.

I am distant was being an expert, but you should be able to get 2400 fps with the 350 gr. bullets. I have used RL-15 to get there, without any obvious signs of high pressure.

Bullet momentum:

(350 gr)*(2400 fps)/7000 = 120 ft-lb/sec

Bullet energy:

(350)(2400)^2/((7000)(32.17)(2)) = 4476 ft-lb

Thanks