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[Seth Hawkins]

 

[Pettifogger]

Most of them are .452 - .454.  They are true .45s and not .44s as barrels are measured in modern times.

[Fox Creek Kid]

They are all over the map and you have to slug them to be sure. Many chambers were oval on 2nd Gen. guns because they roll engraved after drilling the chambers and consequently sometimes too much force squeezed the cylinder too hard. I've seen many 2nd Gen. Dragoons run 0.462 - 0.464  (yes, that's a SIX) groove diameter as well. On any gun you need to slug the bore and at least two chambers as the proper way is to size bullets to fit the chamber & not the bore.

[Long Johns Wolf]

FCK: Size bullet to fit the chamber and not the bore? I don't know about that.
SH: One of my 2nd gen Colt Armies S/N 207514 has .458 rifling groove dia whereas the chambers are .448, i. e. accuracy is predictable lousy unless you can use hollow based bullets. The 2nd gen Colt Army bore of a pard of mine is .462 (but I don't know about the chambers).
In my book chamber & rifling groove dia should be adjusted the same ideally for optimal accuracy. No matter if you shoot a C&B or cartridge revolver. My 0,02€.
Long Johns Wolf

[Hoof Hearted]

I'm more than willing to slug the bores.
Can anyone tell me how to measure the slug?

The way I do it (seems to work close enough) is to turn the "slug" with slight pressure on the calipers and record the largest diameter. Then size the chamber mouths to one thou or so larger. Should shoot fine!

Conversely you can just cast real soft Heeled bullets and load BP, they will bump up to bore size (worked for Colt 100 yrs ago).

[Fox Creek Kid]

FCK: Size bullet to fit the chamber and not the bore? I don't know about that...

Of course, I meant if the chamber is the same size as the groove or a 0.001 - 0.002 larger, which is ideal. The problem one encounters with bizarre diameters is finding or casting bullets to that size. I have a buddy who had a round ball mould for 0.470 for his 0.464 Dragoon.    On a cap 'n ball you can sometimes get away with shooting an undersized ball, but with cartridge guns most won't shoot worth a damn until you have the chambers reamed out to correct size.