Chambers, Groves, and Bores...oh my!

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ClemBert

New member
A little fun with numbers here. Thought I'd get a thread going here pertaining to Caliber, Bore, Groove, Chamber, and Ball size. I was reading a BP thread on a British forum and it seems like they are all bonkers over caliber specifics. Apparently, it has something to do with obtaining a license to buy a BP revolver.

I've posted the specs below on two blackpowder revolvers. So a couple of questions come to mind such as: What makes the ROA a .45 caliber while the Remington is a .44 caliber? Is it typical or atypical that the ball, in a BP revolver, is swagged down to the inner barrel/groove diameter?

From the specs it appears the ball, for the ROA, is swagged down making contact with the inner surface of the barrel. In other words, not only does the ball make contact with the lands it also makes contact with the entire inner surface area. With the Remington, on the other hand, it would appear that ball rides on the lands without contact with the inner barrel surface (the grooved dimension if you will).


Ruger Old Army
Caliber: .45"
Lands/Bore Diameter: .443"
Groove Diameter: .451"
Chamber Diameter: .453"
Ball: .457"

Uberti 1858 Standard Remington
Caliber: .44"
Lands/Bore Diameter: .440"
Groove Diameter: .460"
Chamber Diameter: .450"
Ball: .454"

The data came from the specs listed in the Dixie Gunworks catalog. I wonder if the groove diameter listed for the Standard Remington is in error. Although, if a typo, Dixie has the Standard and Millennium Uberti's with .460 groove diameter whereas the Stainless version is listed with a .452 groove diameter.
 
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mykeal

New member
The only thing that makes an ROA a .45 (vs a .44) is Ruger's marketing department. Unfortunately there's really very little standardization on how to designate 'caliber'.

As for the Remington grooves: I'd have to say that number (.460") is a typo. None of my .44's (or .45's) have a groove diameter like that. .450 would be more reasonable.
 
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ClemBert

New member
I know Ruger started off stamping the ROA with .44 caliber then at some later time .45 caliber even though the dimensions didn't change. I'll have to look but I think both of my ROAs aren't stamped at all with a caliber.

It would still appear from the specs that the ROA does swag the ball down and allows surface contact with the inner barrel whereas it looks like the Remington listed has the ball riding on the lands only.
 
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Ricklin

New member
Why call them fourty fours?

They shoot a .451-.457 diameter projectile. Why would we call that .44 caliber? They are a .45 in my book.:p
 
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whosyrdaddy

Moderator
Ricklin - My S&W Model 60 has .357 Magnum on the barrel. What caliber is it?
Click to expand...

:D 38 special :D

Seriously, I do remember reading somewhere that the official Government position on this is land to land, unless your talking artillery, then it's barrel length divided by bore diameter.
 
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Raider2000

New member
Hmmm, my Pietta w/ 5.5" barrel came with:

Lands/Bore Diameter: .4400"
Groove Diameter: .4495"
Chamber Diameter: .4460"

It shot my .457 ball just fine but I wanted to get her shooting conicals just as good if not better so I reamed the chambers to .4510 & along the way did a few other minor detail work on it & now it'll shoot a .456 220gr. Lee cast conical as good as I can with a ball using 30gr. FFFG.
 
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B.L.E.

New member
In the muzzle loading era, the caliber was the diameter of the bore before the rifling was cut. By this definition, most .45's are really .44's, even the cartriage shooting guns.

As breech loading and unpatched bullets came about, it started to become appearant that it was important for the bullet diameter to match the groove diameter of the barrel for accuracy and so barrel makers began to standardize the groove, not the bore diameter and so caliber designations slowly shifted to define the groove diameter thus .30 calibers became .308 caliber guns etc.

The .38 special and .44 special evolved from a even shorter round that used to be loaded with heel bullets, like a modern .22 long rifle. The part of the bullet that fit into the case was reduced in diameter but the rest of the bullet was the same diameter as the outside of the case.
These kind of bullets worked well in straight sided chambers that you had in old cap and ball revolvers converted to shoot cartriages.
Heel bullets had the lube exposed and picked up dirt from pockets easily so ammo makers switched to inside bullets where the lubed part of the bullet was inside the case like modern .38 specials. Of course, accuracy was abysmal with these undersized bullets and they even experimented with hollow base bullets that expanded to fit the bore.
Later, when they made the bullets longer for more powder and came up with the .38 and .44 specials, they kept the inside bullets but gave the new guns barrels that fit the dimensions of these bullets, thus the .38 special is really a .357 and the .44 special is really a .429, but they kept the old caliber names for some reason. Probably tradition. Maybe .38 and .44 rolls of the tongue better than .357 special and .429 special does.
For some reason, the .44 special did not become the .429 magnum, probably .44 magnum sounds better.
 
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Dingoboyx

New member
I have ROA and Pietta 1858 NA

I squish .451's into both of them and they work fine. I didn't know any guns run the ball on the lands not the not the grooves? Surely this idea would mean the sealing of the gas from the charge would blow past the ball? I thort thats why BP guns only use pure soft lead in their ball, so when they get the hurry up by all that pressure behind it, the hot, soft lead would contact the lands and grooves making a good seal?

Are Pietta's the same as uberti's? I might have to do some amateur ferensics and shoot a ball into a tub of water and see how much of the ball touched what part of the barrel?

Muzza
 
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B.L.E.

New member
I squish .451's into both of them and they work fine. I didn't know any guns run the ball on the lands not the not the grooves? Surely this idea would mean the sealing of the gas from the charge would blow past the ball? I thort thats why BP guns only use pure soft lead in their ball, so when they get the hurry up by all that pressure behind it, the hot, soft lead would contact the lands and grooves making a good seal?
Click to expand...

One of the reasons that the Ruger Old Army is the standard for cap & ball target shooters is that the chamber diameter allows a groove diameter ball to be fired. The ball starts off as a .457 but becomes a .452 after the ring of lead is shaved off.

Some people have reamed the chambers of Colts and Remingtons to allow a groove diameter ball and have reported better accuracy, this requires a custom ball mold because it's hard to buy .460 or .461 balls.
 
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Ricklin

New member
Well .357 of course

Mykeal: I understand what you are saying. But it does fire a projectile that is.......357 in diameter:)
 
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