Why So Many Different Calibers??????

[oldracer]

I was reading Major Roberts' Caplock Rifle book for about the 10th time the other day and it suddenly dawned on me that there seemed to be a lot of different calibers, I.E. 33, 37, 36, 42, 44, 45, 51, 66,etc,etc and of course the ones we see today like 45 and 50 caliber. There seemed to be no mention as to why except to say many old time rifle makers had their "most accurate" caliber and tended to make the same size.

I am thinking that the bore they settled on was due to the bore tools they could make and what they ended up with? Does that sound about right or are there different reasons I missed?

[DIRT Farmer]

If the reamer for the scelp welded barrel came out 42 cal, the gunsmith just built the rifling bed to fit and cut the mould to match.

[Squeeze]

https://www.youtube.com/watch?v=lui6uNPcRPA

[Wayne Smith]

Every time the barrel was 'freshened' it increased in caliber, too.

[Beerd]

same reason we have .223, .243, .257, .265, .277, .284, .308, ................................... in cartridge guns today.
everyone has their own idea of what works best in a certain situation.
..

[Grump]

Well, .54 and .58 in the percussion era were settled on because of a long series of arsenal testing.

Of course, that doesn't address WHY those two sized existed before the testing began. At least I think the .54 did. AFAIRecall, .58 was just copying what the Brits had recently adopted, because it worked rather well with the Prichett Ball, kicked less and used less lead and powder than something in the .60s (back to .69??) with less wind drift in the newly-interesting longer distances.

In the flint days, smaller calibers were squirrel rifles, then in the percussion era longer projectiles were found to shoot flatter, and going smaller bore tended to follow the technology that made each incremental improvement possible. I think the tightly packed powder charges of the .45-70 reduced fouling, for example.

[lobogunleather]

Prior to about Civil War years the caliber of rifles was most commonly called the "bore", referring to how many balls of the proper diameter could be cast of one pound of lead. This carried over with smooth bore weapons (shotguns of 10, 12, 16, 20 bore or gauge, etc) but was generally replaced by caliber designations (in the US this was in inches, in Europe this was in millimeters).

Thus a rifle shooting a 70-grain ball was referred to as a "100 bore", a rifle shooting an 80-grain ball was a "88 bore", the 90-grain ball was "77 bore", and so forth. A .50 caliber rifle using a 180-grain ball would be a "39 bore". So, the smaller the "bore" designation the larger the diameter of the projectile.

In frontier regions, far from sources of supply, folks tended to economize. A rifle that was capable of more shots per pound of lead and powder was considered more useful and economical than larger bores, minimized the need to purchase larger quantities, and made it possible to stretch expensive supplies out for longer periods.

As others have postulated, I suspect that individual rifle makers kept a limited supply of the hardened steel rods used in barrel forging on hand. As the "cottage industry" aspect of gun making caught on in Europe and America some makers specialized in barrels, others made locks, some made brass or silver mountings, and individual rifle makers acquired parts from several sources with which to craft an order to customer specifications.