I bought a 9 mm cylinder to put in a non convertible Blackhawk. I needed to shorten it to fit and balance both front and rear clearances. I didn't want to file on the barrel nor remove it to shorten it. I ended up with a good shooter and 0.004" cylinder gap.

Just based on my one experience they may be fitted to the gun. In either case they are fun shooters.

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Front sight and squeeze