Cacciatore,

I have the same gun in .45-70 and I reload to the 450Marlin
levels regularly. I do not find the porting to be a problem. My non-ported .375 UM is noisier than my GG. The Marlin factory is no longer porting the GGs so if you buy a new on there is no worry. The ports do a great job with muzzle jump and the Guide Gun, in either caliber, doesn't deserve the bad press it has gotten for noise and recoil. It's the gun I grab going out the door when salmon fishing and sharing the streams with the brownies......handy rifle, I shoot mine a lot.

Joe