There's no way I can keep this down to 4 guns, even with the caliber restrictions. Especially since I'll probably (like many others here) going to be loading the bullets in other cartridges.
For everyday carry, a .460 Rowland 1911 built on a STI Tactical frame, and a Glock 30SF as a backup
Kriss Super V SMG, and Kriss KARD pistol for when the gear gets tossed on. All of them using the same magazines is certainly handy. Goes with the Glock 30SF too
8" Saiga 12 select fire shotgun.
Magpul Massoud carbine w/ masterkey.
M1A w/ Krieger Heavy Barrel, Troy MCS chassis and Magpul PRS stock.
DTA SRS Covert Chassis, with the various conversion kits (.308 covert, .308, and .300 win mag), for when I have to reach out and touch something.