A turn off pistol

[fernando]

Hi Fernando

Originally Posted by Fernando K

gbxfb:
What do you mean by "imperial bore size?, Are you referring to the number of rounds per kilogram? ...

gbxfb is surely referring to the bore (gauge) system, which is the number of bullets (balls) per pound. Assuming that your pistol caliber would be 21 bore, that would correspond, as he says, to an approximate 15 m/m caliber.
You can check the caliber of your pistol barrel, although i personaly keep thinking that the 21 is a number and not a measurement. Now that you say that you also see it in the hammer, i would not further suggest that its purpose is the barel/body marriage but that of assembling the various components together, among the several ones made in each lot.

Before production automation was developed, each same gun part was not precisely equal to the next one, so the different components of each gun that were subject to work with precision, were hand adjusted to each other during the making process; this assured that, after the various parts being diverted to finishing treatments, final control and the sort, the number in each component would allow to join back the parts that were tuned to function together.
These numbers usualy seen are very low, as this hand making process was repeated in limited production lots.
Please consider this approach as a suggestion, and not as an exact statement . The process i have described did indeed exist, but i can't guarantee that your number 21 in associated to that.