What classifies a small/medium/large(big) bore rifle?

[Deja vu]

The other day I was at the range and a guy said his 338 was a big bore rifle. I did not say any thing but I thought that it was a very powerful rifle but in my mind a big bore rifle has a caliber that starts with a 4. While Medium bore starts with a 3 and small bore starts with a 1 or 2.

So is there a definition of "big bore" Vs Small bore?

[kilotanker22]

I consider 17 through 264 small bore 277 through 338 medium bore and up from there big bore

[sc928porsche]

Most consider 6 and below to be small bore, 6.5 to 375 medium bore and above that large bore.

[FrankenMauser]

Everyone has a different idea of how to define them, including me.

My own opinion:
up to .20 = Small caliber (or "sub-caliber" - even though it's improper use of the term)
.22 to .257 = Small bore
6.5mm to .375 = Medium bore
.40 and up = Big bore



But, you may notice that most "official" references to the term 'small bore' are almost universally citing .22 rimfire rifles. They aren't necessarily defining the term, but setting standards or rules for a type of competition or event.

Likewise, most references to 'big bore' are almost universally citing .40+ bores, but not really setting a hard limit; and they generally don't include cartridges like .44-40.

[Bart B.]

In NRA competition, small bore refers to .22 rimfire rifles.

Years ago, a neighbor who hunted big game in Africa said the British system called small bore anything below 30 caliber. Medium bore was 30 to 40 and big bore was any caliber over 40.

There's probably a few different naming conventions. Different strokes for different folks. . . . . .

http://www.chuckhawks.com/medium_bore.htm

http://www.chuckhawks.com/intro_big_bore.htm

[B.L.E.]

I think a better way to classify them is

small game calibers
deer calibers
American big game calibers
African big game calibers

It's bullet energy as well as bore. A .44 Magnum is certainly not a African big game caliber.
FWIW, Africa has small game also and calibers such as the .22Hornet are actually quite popular there.

[Rifleman1776]

The beauty of the American system for designating caliber is there is no system. It doesn't make sense and that is the way it is. It is also what makes a lot of our discussions fun. Americans like to do what they want the way they want. Europeans like everything neat and welll organized. I call that boring.
Small, medium, large? Pick yer pizzen and enjoy.

[alex0535]

I think a better way to classify them is

small game calibers
deer calibers
American big game calibers
African big game calibers

This seems like a good way to look at things.

[FrankenMauser]

This seems like a good way to look at things.

That's essentially what the old European system was designating.
With black powder as the most common propellant, and a major limitation to cartridge performance, all that really mattered was "how big and how heavy".
Bullet diameter and weight determined what the cartridge was good for.

Later on, you had terms like "Express" added to some cartridges, to designate light bullets at higher velocity (rather than the "standard" for the cartridge).

With the introduction of Cordite and Smokeless powder and expanding jacketed bullets, most of the small/medium/large-bore references fell apart. It was a new era, where each cartridge could be judged on its own merits, rather than just bullet diameter and weight.

[Deja vu]

I think a better way to classify them is

small game calibers
deer calibers
American big game calibers
African big game calibers

I like that as well.

Years ago, a neighbor who hunted big game in Africa said the British system called small bore anything below 30 caliber. Medium bore was 30 to 40 and big bore was any caliber over 40.

that is the way I have always thought of it. It is a fine way to compare the bore but just because gun has a bigger bore does not mean its more powerful. The 50GI is 50 caliber but it is a pretty weak round compared to other handgun round even more so when you include rifle rounds.

[Jimro]

8 mm and below is small bore. The German 8x57IS was the biggest of the cartridges allowed in "small bore" competitions. I guess since the competition rules have moved on the definition may have changed.

8 to 10 mm is medium bore. You will find a lot of reference to the 375 H&H as a "medium bore" round.

Over 10 mm is big bore.

In America small bore is now synonymous with rimfire, although I don't know how that developed. In some countries "fullbore" refers to a service rifle competition (in 308 Win).

Jimro