Not an expert, but love to learn about any gun/caliber. My favorite to learn about is .357 revolvers.
A great place to learn obscure information is on the ask the experts forum @ the Gunbroker Forums. I browse that all the time just to read about interesting firearms.
Ha, the military ensured I leaned all I ever wanted to know about 106mm, 7.62, 5.56, .45 ACP and 9mm.
Now a days my personal favorite is the 10mm and hopefully I will know more about than any other caliber.
I am also a phase person! Or, if something interests me, ill take a note or two! When I either buy, or am about to buy something, I learn what I can about it, so I can do what I need ro with it. Or, i'll try and learn as much as I can about a friends firearm, so, an Enfield No. 4 Mk. 1(.303), Beretta 92FS, Norinco Tokarev 54-1(9mm), and a Bushmaster AR-15 M16A3. So far, for me its been Yugo M48 Mauser, Mosin Nagant M44, Romanian AK-47 WASR-10, then Colt M1911A1. Calibers were 8mm, 7.62x54R, 7.62x39, then .45 ACP(All rifles, pistols, and calibers in that order). Soon, hopefully, an AR-15 of my own, or a Glock 17.
I guess in my 56 years I have killed more things and shot more things with a .22 rifle or pistol than any other caliber out there. I have shot steel targets, paper targets, bottles, cans, walnuts out of trees. Most fun and the cheapest ammo.
AR15's here. I've built a bunch. I love em'. I'd like to no more about the M1A1's but the cost is killer. Anybody want to loan me about $1800.00 til my hunch back brother straightens up ????