doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 36 ga?

So what gives with the 36 ga nomenclature for the .410 bore? Is there some secret to gun makers that we have yet to uncover, or just an easier way to keep continuity i.e. 12 16 20 24 28 32 36?

in fact, the .410 bore is equivalent to a 67 gauge


https://www.americanrifleman.org/articles/2017/12/6/rifleman-q-a-is-410-a-gauge/



In 1961, the �Permanent International Commission for the Proof of Small Arms� (generally known as �C.I.P.�) finally settled on a designation and standardized measurements for the .410, reversing its earlier decision to use the inaccurate description of �36 gauge� (it would actually be a 67� gauge).

It was not to last. The dithering by the Commission, for over 70 years, as to what the official name for the gauge should be had lead to the long-term adoption of the terms �36 gauge� for the 2" & 2�� shells and �36 gauge magnum� for 3" shells in mainland Europe and these were too well established in the minds of users to be changed arbitrarily. In 1969, the name �36 gauge� was appended to the official name in parentheses and thus it has remained.

http://www.smallboreshotguns.com/410-bore/

It's all a mixed up deal. British proof houses accept .405" to .415 as the range of bore sizes for a .410. It takes 67 balls of .410 diameter to be a pound. Thus, it is truly a 67 gauge.

There actually is a 36 gauge, at .506" bore diameter, and Eley loaded shells for it. There's a picture of a box of them in Gabriel's .410 book. There was also an even smaller than .410" chambering ......... a .360" cartridge of 1 3/4" length and carrying 3/16 oz. of shot.

So, how the .410 ever got the mistaken identity of 36 gauge in the first place is a mystery to me. Same reason a largemouth bass is still called a "trout" in parts of the Deep South, I guess.

SRH

Just go metric and call it 12 mm --

Calling it a 12mm would also be inaccurate as a 12mm is actually .472.
Being one who carries a 10mm handgun everyday I knew that 12mm was much larger than .410 as a 10mm is 40cal.
The outer diameter of those shells may have been 12mm.

12 mm = .47244" . This, of course, is not the bore size of a .410 shotgun but would fall within the chamber dimensions.
As stated 36 gauge = .506", obviously not a .410.
a .410" bore size per both British & German proof charts = 67.49 gauge.

Some gauge charts only go down to 50 (.453") but there are others, more complete, which continue @ .45" & go down to .30" in .010" increments. these are;
.45" = 51.04 Ga
.44" = 54.6 Ga
.43" = 58.5 Ga
.42" = 62.78 Ga
.41" = 67.49 Ga
.40" = 72.68 Ga
.39" = 78.41 Ga
.38" = 84.77 Ga
.37" = 91.83 Ga
.36" = 99.7 Gauge
.35" = 108.49 Ga
.34" = 118.35 Ga
.33" = 129.47 Ga
.32" = 141.95 Ga
.31" = 156.14 Ga
.30" = 172.28 Ga

This could be extended further as;
7 mm = .276" = 221.24 Ga
6.5mm = .256" = 277.25 Ga
6mm = .236" = 353.88 Ga
5.6mm - .220" = 436.84 Ga.

You can take 16 & divide by any gauge no & it will give the weight of the round ball in ounces or divide by 7000 & it will give the weight in grains.
Probably more than anyone wanted to know, but that's the scoop.

Regardless of how widely used or how much accepted either 12mm or 36 gauge are total MISNOMERS, for a gun with a .410" bore. either smooth or rifled. In metric its a 10.41. Remember the old 10.4mm Swiss Vetterli rimfire (.41 cal) while in gauge it is as stated a 67.49.

I could be wrong but my personal belief is the original promoters of it just didn't want people to truly realize just how LITTLE the thing actually was. 36 gauge sounded bigger than a 67.49 & 12mm sounded bigger than a 10.4mm.

Awesome! Thank you guys!

Don't conflate the nominal gauge of the chamber with the bore diameter (in gauge measurement). The most common 12 ga, as we see from German proof marks, often have 13 ga. or 13/1 ga. barrels. The actual bore diameter in both smooth bore and rifles, very often don't match the nominal chamber.
Mike

Very True Mike, & a good point. The chart I posted was from the proof houses & indicates the "Correct" size of a bore, based on a pure lead, perfectly spherical ball that will exactly fit. It certainly was not meant to imply that every 12 gauge, for instance, that has ever been built left the factory with exactly a .729" bore diameter.

For many years the proof housed measured the bores with a series of plug gages. The barrel was marked according to the largest gage which would enter the bore to the prescribed depth. This then denoted a "Range" for the size & not an exact dimension. 13 = .710" diameter thus a 13/1 = .719. A barrel marked 13/1 at proof thus meant it would accept the .719" plug but would not accept the .729" one. It could have been anywhere in between.

The point is though all of these other sizes were named for their "Nominal" bore size from which their chamber sizes were developed. The bore sizes themselves hark back to muzzleloader times. When breech loaders were developed the guns were no re-named for their chamber size but kept their name according to their nominal bore size. "IF" they had been renamed according to their chamber the 12 gauge would have become approximately a 9 gauge (.8025") which would have fallen about mid chamber.

As stated earlier 12 mm falls within the chamber diameter of the .410. 36 gauge (.506") is even well beyond that, Neither is an indicator of the actual size of the .410's (67.49 gauge) bore.

Fourteen years ago I owned both a .410 SXS with no chokes and a true 36 gauge percussion SXS with no chokes. I did a write up for the fourteen website which included a photo of the two guns muzzles displayed side by side. Below is the link to my write-up.

http://www.fourten.org.uk/36g410.html

Steve