I have a .458 win mag I do all of my loading for. I've never shot factory loads through it yet, maybe never will.

I would like a couple suggestions for trying to duplicate the recoil of a 375 h&h and also a .416 remington mag.
I'm sure this is doable. The only thing I'm not sure about is the differences causes by the different bore diameter. Maybe a 300 gr bullet at the same velocity, but of different calibers recoils very similarily. But I would expect that things like chamber pressure do matter, I just don't know how much.
It should be a good idea for introducing a person to the recoil of different calibers. It takes away all other variables. For example, if the gun fits them well enough and they are fine with the recoil of the .375 but they hate the recoil of the .416 and the .458 then there might not be any need to look into it any further. Get them a good .375 and make it fit them. I'm sure you get the idea.

Here's an online recoil calculator. With this, a chronograph and some range time, you should be able to duplicate recoil and recoil velocity.

http://www.handloads.com/calc/recoil.asp

You can't change the laws of physics; given an identical rifle, identical bullet weight, identical velocity, and identical powder charge weight, the recoil will be the same. Pressure does not enter into the equation. Now, you will use different powders and weights, so that is really the only variable you have to work with. Caliber is not part of the equation either.
Practically,just get a 300 grain bullet going at the same velocity as a 375 does, and you will have it. 416, same idea with a 400 grain. Your idea has merit;

Frank...Try the Cutting Edge .458 cal. 300 gr. ESP Raptor bullet. I just worked up a load with 62 gr. Of IMR 4198 and Fed 215M primers. 2,500 fps average velocity and superb accuracy. The best part is mild recoil...comfortable to shoot in an 8 lb rifle. I was going to take my .375/338 brown bear hunting this spring....but really wanted to take the .458. Now I'm gonna!

Phil

quote:

Originally posted by PhilR:
Frank...Try the Cutting Edge .458 cal. 300 gr. ESP Raptor bullet. I just worked up a load with 62 gr. Of IMR 4198 and Fed 215M primers. 2,500 fps average velocity and superb accuracy. The best part is mild recoil...comfortable to shoot in an 8 lb rifle. I was going to take my .375/338 brown bear hunting this spring....but really wanted to take the .458. Now I'm gonna!

Phil

That's kind of ironic, I ordered some this morning.

I made up a load in my 458 for my wife to use when she was my bear watch 12 years ago.
300 gr TSX @2500 fps using IMR 4198. She could shoot it ok. Anything heavier or faster, not so much. It was like shooting a 338. Very.mild and easy to shoot but with sufficient snort to keep from getting bit or smashed. . At least I'm fairly sure it would. Never had to shoot a bear with that.load. The 375 is a good bear round so I figure it would be at least as good as a 375 mag. Possibly better as the bullet.is wider.