I concur that at the bottom is the .22 BB or perhaps CB cap round, and at the top...

I guess there's room for controversy here! Of course, one could include the .50 BMG round, but any weapon that fires this is hardly what one might callportable! They are fun to shoot, but not much fun to carry afield unless you have two gun bearers or at least one horse! Yes, you can set one up on a benchrest on the side of a mountain, and shoot across at elk or moose beyond the next canyon.

However, there are some large caliber riflesthat are more or less man-portable, such as the .577 Nitro, the 600 Nitro, and now the 700 Nitro. These may not deliver the same amount of energy you can get from the .460 Weatherby, but there are some for whom foot-pounds is not a valid expression of killing power!

And, if you want to discussREAL big-bore rifles, there are the 8-bores (.83 caliber), the 4-bores, which fire 1/4 pound round balls or even heavier conicals, and the ultimate man-portable shooting machine,exemplified by Sir Samuel (Pasha) Baker's "Baby", (Son of a Cannon-"Jinnah-Al-Mutfah"), the2-bore which fires 1/2 pound round balls. Pasha Baker said that firing "Baby" gave him a headache and a nose-bleed at every shot!Most of these big rifles were (are!!) black powder muzzleloaders, but in the Metzger Gun Collection at Texas A&M University is a single-barrel 8-gauge breech-loading rifle. I don't know if it used smokeless powder or not, but it could have.

(Why anyone would fire such a contraption is beyond me, because a piddling 10-bore of a mere .75 caliber (10 balls per pound) will kill anything on this planet!)

Now, here's a pic of a 4-bore breechloader with cartridge! Looks like it'd be fun to fire THAT!!