Bore diameter.

[Shooter1]

Ahh, to be young again and be adding to the gun vault and shooting bench....

 

[andy52]

Ahh, to be young again and be adding to the gun vault and shooting bench....

I'm 70 years old and still adding to the gun vault...

 

[SmokepoleSam]

I'm 77 and have just about stopped adding to the pile (looking for a left-hand long rifle) but I've only sold one gun so far. Have to get moving on that, I have some guns I've never shot and have had for years.

 

[Shooter1]

I've got one I acquired while very ill. Need to go out and make smoke--soon.

 

[Col. Batguano]

Is your gun of English origin? That bore size would roughly correspond to a 40 bore rifle. That's the reason we see so many guns of that caliber. The Europeans tended to work in "bore", and Americans in "caliber".

 

[andy52]

Is your gun of English origin? That bore size would roughly correspond to a 40 bore rifle. That's the reason we see so many guns of that caliber. The Europeans tended to work in "bore", and Americans in "caliber".

yes, it's from England. The bore measures .425 so it could be a .40 but it would need a really thick patch.
I've never owned one like this before, I know they're loaded from the breach and may not even use a patch.

 

[Col. Batguano]

I think I might not have explained it as well as I might have. Anecdotally, I have a Purdey SxS 40 BORE rifle that is .48 (calibre) across the lands, and .52 (calibre) in the grooves. It is marked 40 BORE under the barrels (which isn't what that CALIBER would be). The seller (James D, Julia auction) mistakenly labeled it as a 40 CALIBER, but I suspected otherwise, which was born out when it arrived.

Here are the Gauges (or bore size) for common calibers of rifles.

.32 cal. ( .320) - 142 gauge.
.36 cal. ( .360) - 100 gauge.
.40 cal. ( .401) - 72 gauge.
.45 cal. ( .450) - 51 gauge.
.50 cal. ( .501) - 37 gauge.
.54 cal. ( .531) - 31 gauge.
.58 cal. ( .579) - 24 gauge.
.62 Cal. ( .615) - 20 gauge.
.66 cal. ( .662) - 16 gauge.
.69 cal. ( .693) - 14 gauge.
.72 cal. ( .729) - 12 gauge.
.75 cal. ( .751) - 11 gauge
.77 cal. ( .775) - 10 gauge.
.83 cal. ( .835) - 8 gauge( or Bore)
.92 cal. ( .919) - 6 gauge( or Bore)
1.0 cal. ( 1.052)- 4 gauge( or Bore)
1.3 cal. ( 1.355)- 2 gauge( or Bore)
1.7 cal. ( 1.669)- 1 Gauge( or Bore)

Here's another link from the British Militaria Forums that speaks to the same;

https://www.tapatalk.com/groups/bri...nglish-bore-to-caliber-conversion-t11574.html
Your .425" caliber looks like it might roughly correspond to about a 60 bore.

 

[david w]

I’m thinking a .490 ball will be too big. I’m not an expert on commercially available sizes, but I’d be looking at something in the .470 or .475 range which could be hard to locate.

My understanding is that a lot of the original rifles were inconsistent in bore size, and the builder included molds that fit that gun.