Re: remington model 7's
The model 7 is just a bit shorter than the 700 Short action. Its magazine measures 2.8" max. The safety set up is slightly different, the trigger can be used w/ either but you will have to use safety from Model 7 set up. You can't use a model 7 in a 700 short action stock without changes to stock, not worth the time in my opinion.
They are good actions though, I did have a barrel from my 700 short action installed on a model 7, it was a 358 Win Shilen w/ muzzle brake and became a 350 Rem Mag, the barrel is still 22".
Pa Griz, probably because the cartridge was made for a LA is why your gunsmith said it wouldn't work.