so had a silly idea, in my never ending quest to iron out the details of an awesome to carry and miserable to shoot 375.....i thought to myself why not grab a kimber mtn ascent in 300wsm whack the barrel to 18-20 inches get a jes rebore and run a 375 wsm reamer through it.....have irons added and slap a small leupy on top and send it.......also seems like the same idea could be applied to a 300 win mag and end up with a 375 ruger.

I can't tell you about the 375 Ruger, but I had JES do a M70 Classic from .270 WSM to .375 WSM. I am a happy customer. The chamber seems to be on the tight side - I have to really crank down the seater to get brass that fits, and I had to inside and outside neck turn after sizing up Nosler .300 WSM brass to remove a brass "doughnut" at the neck-shoulder junction. I did one piece of RCC 325 WSM brass and the result was the same. I'm using a K&M neck turner, and it was a ~$200 setup with the carbide inside cutter factored in. The inside cutter really only works with a drill powered setup also - it's too much to turn by hand IMO.

It's pretty cool now that it's working though. I should be able to get a 300gr soft or solid at >2450 ft/s with temp stable powder when all is said and done.

Assuming it shoots well with a scope I'll have NECG put on express sights.

I can't see any reason other than weight not to do a Kimber. I like the M70 Classic action much better, but if the Kimber's you choice I'd say go for it.

It would make for a very thin barrel wall, but it may not be a problem with a short barrel.

I’d imagine that the 375 WSM would have more capacity than the 375 Whelen AI, but they should be close for velocity, I’d guess.
I really like my 375 WAI, but it’s quite a bit heavier than what you’re talking about - laminated stock, Mauser action, and heavier and longer barrel.
I’d think that if you are looking for loads you might look at 375WAI starting loads and work up.
That rifle - seems very light - per what you’re describing, might be a handful when shooting. I’d be interested in reading the results of your build.

I believe JES requires 0.1" on each side. So you can measure at the point you intend to cut and see if there's enough.

The Whelen AI would be about 10 grains smaller and about 80-90 ft/s slower at the same barrel length and pressure.

Sounds like a pretty nice conversion....and while I don’t know the exact weight (scoped, loaded, slung)..... I’m guessing that recoil should be quite manageable. The rifle should be a “dream” to carry! memtb

Could do most of the same thing with a 376 Steyr (OAL 3.110”) and a scout type setup. Most .375 bullets load at an OAL of 3.065” - 3.085”. Find a 3.2” Mauser length action or go with standard 3.4” action. Feeding would be easy, brass from Hornady would be spotty. When offered you’d have to buy in quantity. The 376 offers great ballistics in a 20” barrel, 270 gr at 2,525 fps, 300 gr at 2,450 fps. No wildcatting, standard SAAMI chamber and ballistics that meet your current requirements. Just a thought.