Smoothbore newbie

[R Ellis]

the proof marks are not really confliction first you find the mark that defines which proof house it was proofed in then use the chart for that proof house and you cah find the year and month and chokes or cylinder etc.

 

[Sidney Smith]

I've got a .62 caliber (20 gauge) smoothbore, cylinder bored, as in no choke. I've used it to hunt squirrels, turkeys and pheasant. I keep my shots within 30 yards. Past that and you're wasting powder and lead.

 

[Grenadier1758]

If I read the 3 numbers correctly, I see 17.6 (mm) or 0.693". That's consistent with the bore diameter you measured. I think @Gsyme's SxS is a 14 gauge cylinder bore. Do the patch test to see if there is a choke. Tight at the muzzle and loose toward the breech.