MkII M77 Rugers made easy going from 7mm Rem. Mag. to .416 Taylor
and from .338 Win. Mag to .458 Win. Mag., no feeding issues for me.
If the Hawkeye mag box is that much different for the .375 Ruger and .416 Ruger compared to 7mm Rem. Mag.,
maybe the parts could be ordered for replacement ?
That would be a good research project.
Dave Scovill was able to get the RSM sheet metal box for a .375 H&H and convert/re-barrel a MkII M77 Ruger to .375 H&H.
BTW, I re-barreled a 7mm Rem. M70 Classic to .264/.375 Ruger (aka .264 Ripmoor, my own version of wildcat), no feeding issues.
I just put 3 of the .416 Ruger into my .458 Win. Mag. made from a .338 Win. Mag. MkII Ruger M77.
Seems to feed smoothly starting into the chamber.
Ditto my .416 Taylor made from a 7mm Rem. Mag.
In my experience the Hawkeye and MkII M77 Rugers are identical in the mag box dimensions.
Polishing feed rails and ramp might be all that is needed.
Put some .375 and .416 Ruger dummies in your 7mm Rem. Mag. action and try it.
"CH Tool & Die 4-D": https://www.ch4d.com/
Yep, CH4D is kind of an odd name, but C4HD would be even more so, hehhehheh.
CH4D dies have been good for me on
.458 Win. Mag.
.400/.395 Nitro Express 3" Aboriginal ... that last one is my own design of wildcat based on 9.3x74R brass.
CH4D has done a lot of 9.3x74R wildcat dies, sort of a favorite of the proprietor, I knew they knew how to do those,
back in the day ... we are all getting older, hope he is still kicking.
I have a .50-110 WCF set from CH4D just waiting for some use to see if they are any good.
If I see them collecting dust somewhere, I buy them, no worries for CH4D quality.