Guys,

Going to use a M70 SS Classic for my light rifle in Tanzania after the 15th of August. I had not gotten out to chrono my .375 H&H Buff loads but was concerned because the charge weight that gave very nice looking brass and primers was only 69.0 gr of RL-15.

The brass was just beginning to show some sxpansion in front of the belt ... about 0.001"

Did chrono today ... temperature shows 90F ... a little hotter than I expect it to be in the North Mahenge. Average of three rounds including the fouling shot was 2600 fps with an ES of 37 fps.

This load is relatively low against loading manual data ... but is getting fast results for a 24" barrel. Could probably come down a little given the slight expansion in front of the belt.

Is it worth bothering to drop the charge weight a little and trying again?

11 days and counting!

Given what you have said............no. Not likely to be too much hotter than 90 and if the load shoots well in your rifle and functions properly you should have nothing to worry about.

I went through a similar scenario with a rifle in .458 Winchester magnum. In fact they were what was considered hot loads by the manuals. In my rifle I saw no such signs. They both worked perfectly on my hunt.

Starling
If you are not experiencing any problems and it is accurate and reliable I wouldn't mess with it.
I have a Win M70 Classic Stainless in .375 H&H and I too have been working on a 300 grain TSX load with RL-15. My best 3 shot group to date was with 71 grains of RL-15 and it shot .5" at 100 yards. No signs of pressure, primer was fine and extracted as if there weren't even an empty case in it. I've not chrono'ed this load but for me if it shoots really accurate and is absolutely dependable I won't mess with it no matter what the chrono tells me.
Above all else whatever you do you must have absolute confidence in the load, the gun and the whole set up to hunt with it effectively. You don't want any nagging doubts when you are about to drop the hammer 10,000 miles from home.
Stay with what you have if it is working, don't over analize a good thing.

Ditto.
Don't change anything if it is accurate enough.
My rifle liked the old Barnes XFB Cannelured .375/300 gr with 72 grains of RL-15, GM215M primer, and WINCHESTER BRASS, which has greater capacity than Remington brass. Velocity in my rig was 2528fps.

What brass and primer are YOU using?

My load was 3/4 MOA in my 6.75-pound-naked-weight rifle when I got the bedding sorted out. It killed all plains game in Botswana, Tuli Block and Okavango. It was easy to climb kopjes with.

I'm shooting the 300 TSX at 2480 (10' from the muzzle) with IMR4064.

Am using Remington brass and Winchester Large Rifle primers ... didn't see a need for anything hotter with RL-15. Rounds were crimped with a Lee Factory Crimp Die.

I was a bit surprized by the high velocity at such a low charge. The diameter of the fired cases just in front of the belt is 0.5110" to 0.5115" which is about the diameter given on several drawings (0.512").

Think I am going to leave it. The other rifle (.416 Rigby) is doing fine and it will probably be used more than the .375.

Good luck I too an going to North Mahange with 300gr TSX out of a Sako 375H&H for a pair of Buff-looking forward to your report.