If you measure the M/F barrels, as I have on two Repro 28's that I've owned--which agree with the measurements given in the current Champlin Arms list for new 2-barrel set they have--you'll find that they are indeed M/F. But for a 12ga, not a 28ga. There must be some use for 28ga barrels choked 019/039, but I'm not quite sure what it is.
Based on my own experience--I also had the chokes opened--I would proceed with caution. There's not a whole lot of meat in those muzzles, and opening them to standard 28ga constriction for, say, IC/M would mean going to 005/010 or 011. Especially with the tight barrel, that's taking out quite a bit. I ended up with ribs coming loose at the muzzle after opening the chokes. I can't say for sure that there was a connection between the two, but the ribs weren't loose beforehand and they became so fairly shortly afterwards.
If you shoot the shorter barrels relatively well, you shouldn't have to go as far with them to get them to something like skt/IC--probably around 003/005 (maybe even leaving the L barrel just a little tighter).
I love 28ga Repros. I'm currently working on getting one that has both DT and barrels that are already about where I want to be as far as choke is concerned. I do wish the Japanese, who otherwise did a fine job on those guns, had been a bit more in line with what 28ga constrictions are supposed to be for a given degree of choke. They came a lot closer on the 20's and 12's.
