I have two Trooper Mk III's, one a 1970 model and one a 1971. Haven't shot either of them very much, so a few months ago I started working up a load for them using Berrys 158gn FP bullets and HP38. Don't remember now where I got my load data, but the length was very long. Using my 1970 model I adjusted the length until the cylinder would turn OK.
Finally got around to trying them last Friday. Shot twelve of them thru the 1970 model OK. Kind of powder puff loads but accuracy was good.
Loaded six into the 1971 model, started to cock the hammer and the cylinder wouldn't turn. Couldn't get the 18 rounds I had to work in that gun.
Yesterday evening I measured the cylinders and they both measured the same. However, holding them up to the light, there was a noticeable difference in the barrel/cylinder gap. Don't have anything to measure it with, but the difference was quiet plain.
The 1970 I got almost new back in 1970 and it has not been fired much over the years. Mainly kept it in the cabinet loaded with snake loads. The 1971 I bought about a year and a half ago. It has a lot of bluing gone off the cylinder and the barrel end, but doesn't appear to have been fired much either.
Just thought it was interesting.