So my new Win M70 .375 is on the way and since I've seldom shot a rifle larger than a 30.06 I thought I'd like to start shooting the .375 with some reduced loads. I've got a couple recipies from my Speer manual but hope some of you can suggest some as well. Thanks.

I used the starting loads from the Sierra manual with their 250 grain slugs. They were a lot easier on my wife than my normal 300 grain plains game loads. She wanted to shoot it enough to become familiar before our hunt.
Thats the route I would take. The full boat loads are not all that bad, the rifle with a scope is fairly heavy, and the stock design manages the recoil VERY well too. You should be OK.

FN in MT

The Hornady 225 grain spitzer with a starting load of one of the faster powders should do. I use 64/H4895 for fireforming cases for the .375 Ackley, and the load is pleasant.

Look no farther than the Hornady manual -- I've preliminarily tried their reduced loads with the 220-gr. flat point using both SR 4759 and XMP-5744 and both are very accurate -- probably a slight edge to the 5744, a fantastic powder for reduced loads.

I use the Lyman .375449GC .38/55 bullet sized .375 in mine, with 60 grains of H4831 and a tuft of kapok to hold it in place. This is an extremely accurate load, gives a vel of around 1800 FPS, and has a recoil close to the .30/'06. Kills deer too, up to 150 yards......