Why was the Colt Navy .36?

[jhon]

I'm wondering why the Colt Navy's are .36 caliber when they shoot .380 or .375 balls? Didn't the cartridge conversions shoot .38 colt? Was the revolver technically a .38? Are the chambers on the new replicas larger than the originals, or was there another reason for calling them .36 caliber?

I don't know much about the technical side, just that they're fun to shoot!

 

[mykeal]

Caliber is determined by the diameter of the barrel measured across the lands, not the cylinder chamber. In order to achieve a gas seal in the barrel and to engage the rifling to spin the projectile revolvers use projectiles that are oversize. They do not have the patch that rifles and single shot pistols use.

 

[unspellable]

caliber

Caliber designations are notoriously lacking in rhyme or reason. It gets far worse when you move on to cartridge firearms. The above is true in that strictly speaking, the caliber is the diameter from land to land while the ball must be a press and shave fit to the chamber mouth. Ideally, the chamber mouth will be 0.001 larger than the groove to groove diameter of the barrel.

 

[bigjohnson]

+1 on what Unspellable said.

A few examples are:
38 WCF (38-40) - actually .401 bore diameter (the same as .41 Colt)
44 WCF (44-40) - actually .429 bore diameter
38 S&W Special - actually .357 bore diameter

 

[Bad Flynch]

>38 WCF (38-40) - actually .401 bore diameter (the same as .41 Colt)
44 WCF (44-40) - actually .429 bore diameter
38 S&W Special - actually .357 bore diameter<

Nomenclature glitch: bore is really land diameter, not groove, although the terms are commonly used interchangeably in informal conversation.

Actually, those are more like the groove diameters and the caliber is, as previously stated, measured as the land-to-land diameter. It is all a relative matter, nominally determined and the Europeans (and others) have different ideas about what contitutes proper bore-to-groove relationships. However, metric caliber designation is very strict about spedifying land-to-land diameter for caliber.

 

[Omnivore]

Jhon: First, welcome to THR!

All comments above are correct. Additionally, when you load a .375 or .380 ball into that slightly oversized chamber, the chamber mouth is actually shaving off a ring of lead in the process. The chamber is sizing the ball, and at the same time creating more surface area, for a better purchase on the barrel rifling. This is one reason why soft lead is used in the cap & ball revolvers, as opposed to the harder alloys used in more modern guns.

Caliber designations can drive you nuts until you've simply memorized a whole bunch of data, as there is no hard and fast rule-- only general ones.

Better to err on the large side for a BP revolver ball. An undersized ball, so goes the common wisdon, can lead to a "chain fire" or to erratic velocity or poor stabilization.

Aside: In naval ship guns, "caliber" refers to the length of the barrel in bore diameters. An 5 inch, 50 caliber gun has a 5" diameter bore and a length of 5 x 50, or 250 inches.

 

[scrat]

+ 1 on what everyone has said. Oh and welcome to the High Road.