Bore, Gauge, & Caliber Meanings:

Now -do you enjoy getting confused? .. Of course not - this is why so many 'Old Farts' (& "Old Fartesses" 😈) are reluctant starters on the smart-phone & internet tech uptake.

.. I still call my 'Flash Drives' - "sticky-up-things"

.. so I decided that I wanted to get clear headed on the issue of bore sizes and gauges - and "pounders".

Well - for starters let's take the .410 Gauge Shotgun ..  WRONG !  It should be '.410 BORE'. - And it might reassure you further that historically this size was also known in Europe as 12 mm which of course it is not because .410 inches equals 10.4 mm.  And just to tickle your fancy even further - this chambering used to be called "36 Gauge" - which is even worse - as If the .410 Bore had been named in the traditional fashion, - by the number of lead balls .410 inch in diameter needed to make one pound, -  it would be either a 67 or a 68 gauge.

- So I'm really getting clear on this already eh.

Over the centuries -the inventor or maker named his "wonder-stoppen-cruncher' whatever he fancied - and to decide what size it was himself. Two "classics" are the 'thirty-eight Special" bullets that measure .357 inch and the 'forty-four' Magnums that measure .429 inches. (Or the 'thirty-twos' that mike-up at .312" including the 327 Magnum that also mikes-up at .312 inch ... Would that .32" caliber be 160 Gauge?).

 Our ancients could choose the chamber size, bullet size, barrel size, or might also pick the weight of the standard gun powder charge as named features.

The whole "SIZE" and "NAME" situation regarding "GUNS" is very confused & complex.

68 Pounder Cannon - Fort Nelson.

What I wanted to find was a chart listing all the Gauges & 'Bores' with a size in inches and the metric equivalents - and maybe a listing of the cannon 'pounders' and their sizes.. but  one chart** that I did find .. might be disputed over.

- Cannon used to be classed for size by the weight in pounds of the iron cannon-balls that fitted in their bore.

GAUGE was determined by the number of bore sized lead balls that add-up to 1 pound.

BORE is a measurement of the actual caliber or internal Diameter of a firearms barrel .. the size of the hole -  BUT while this is mostly measured at the lands (e.g .303" rifles use a .311" bullet) .. sometimes this is measured at the grooves (e.g .308" Winchester rifles use a .308" bullet). Bore may be stated as measured in either inches or meters.

- So which is the biggest slug -  .308" or .303" ? (think about that before answering eh 😈 )

- Bullets for a rifled barrel are normally best sized to the groove diameter.

**   http://www.cherrytreefamily.com/gaugetocaliber.htm

This Chart (linked to above) is very good BUT doesn't agree with some other folks information that I've seen - but when all is said-and-done .. at least he's had the balls to write it down. - Is 38 bore .491" or as said elsewhere .497 inch ? -Is 80 bore .388" or .392 inch as per a late model Tranter Revolver ? - AND might the differences be due to "windage" or allowance for the use of patches?

A nice 80 Bore Tranter.

Probably it's safe to say that it may not matter .. unless you want to build an exact replica of an ancient relic eh.

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- Here's a 'can-of-worms' - what size bullet should you use in a 7.62 x 38R caliber 1895 Nagant Revolver?

 - "Cartridges of the World" says .296" diameter - others say .308, - and I say  .312" because these revolvers were built specifically to use barrels from production of the Mosin-Nagant  7.62x54R Rifle  (.311 / .312") .. Or am I wrong?

Mate & gunsmith Rod has sent an image of an old bore gauge that he uses regularly:

- Thanks Rod.
Marty K.