Biggest is my .58 P53 Enfield. Loudest now is a 30-06. Loudest I ever had was a 30-378 Weatherby with a muzzle brake. Cartridges back then were 90 dollars per box of 20. That was in 99, God only knows what they are now.
I guess my Garand. Not a fan of hard kicking rifles, so my other two are a x39 carbine and AR in 223. I refuse to get anything that leaves a bruise, like the Mosin M38 I had.
Come to think of it the hardest kicking firearm I shot was my Mossberg 500 18" with a slug. OW!
On the rifle range it is my EDM Windrunner in 50BMG. The original 'wasp nest' brake managed to amplify both muzzle blast and recoil. It wears a very effective clam shell brake these days, but you don't want to be in line with the ports when it fires.
On the pistol range it would be my repro Harper's Ferry .58 flintlock with 70gr FFg under a patched ball. Fun to shoot, but not to clean.
I don't own anything all that big anymore, but I sure have made a few.
LOTS of 416s 458s, 460s a 505, and also several 8 bores, five 4 bores and one 2 bore rifle.
Other than my .308's which are loud because of their short barrels, I think the loudest thing I shoot is my short barreled .357 mag Blackhawk. My 12 ga. security shotgun has the worst recoil, especially with slugs.
Wow I thought I would be very overgunned.
Hardest hitting rifle I own and for that matter ever fired is any one of my 30-06.
I always wanted to try a big nitro or 460 wtby mag. I wish I could afford one of those double rifles.
Most powerful in terms of ME is my Ruger #1 Tropical chambered for the .416 Rigby. It is a gun the I have absolutely no use for and which I thoroughly enjoy.
The same could be said for my Winchester M70 in 375 H&H
Loudest? I don't really know.
Hardest kicker? In terms of free recoil, it is the .416. In real, shooting, terms it is a T/C Encore with a fast twist barrel from SSK Industries chambered to shoot this round:
A BMG bullet seated in a 50-70 case. Subsonic, it comes out of the barrel at about 900 fps. Nevertheless, it is the only rifle that has ever caught me with its scope. The recoil pulse is so fast that I could not get my head out of the way. Glad that I had safety glasses on. I had to go to a LER scope.
Pete