Contact a manufacturer, or custom gunsmith.
1592
dugh
If there is not an adjustment built directly built into the gun, then it would be illegal to do so in the United States.
Probably the Chinese.
None
It was made in 1967
Post the serial number of the gun and I'll let you know.
Eli Whitney built the prototype gun locks in 1801
your gun was built in 1910
Impossible to answer since you did not mention the make and model.
It was never actually built.
About 150,000 during the production life of the gun.