Did the model 99A switch to a 24" barrel? I couldn't really find much info about the 99A online. 99B and down, no problem. I have a late transition in 303 dated to 1925 with serial 279xxx still marked 1899 with a heavy 26" barrel. Crescent butt, solid frame, schnabel forend, buckhorn rear and marble #5 bead front. Just wondering how long that lasted and if/when they switched to shorter barrels.
Thx.

Don't quote me but 1926/27

Yes, the barrels were shortened in late spring or early summer of 1927. The 1899 stamp on 99's continued until about the same time and then went away.

A 1925 rifle wouldn't be a "transition" rifle. The post-WWI model 1899's were physically identical to the early 99's from 1921 up until the change that involved shorter barrels, etc. in 1927. The change to 99's in 1921 was mostly just a marketing name change - think of their marketing line as "Hey, we aren't those other lever actions that only shoot wimpy cartridges from the 1800's! We have a modern rifle that shoots a new cartridge that's the same as the 30-06 you used to fight the Germans in Europe!". The most significant physical changes that happened with the 99's were simply more chamberings available in more models, and the re-introduction of the featherweight solid frame which hadn't been made since 1917.

The new 24" barrel was also thinner than the old rifle weight barrel but heavier than the lightweight barrel that was used on the Models 99E, F and G. The E,F. and G also went to the medium weight barrel. From about 1926 until 1955 the 99's were only available with the medium weight barrel. The 20" lightweight barrels on the E, F and G were increased to 22" with the change. This was calibers 22 HP, 303 and 30-30. The 250-3000 continued at 22" and the 300 savage was continued at 24". The medium weight barrel was first introduced in the 99H in 1924. The other models didn't get the medium weight barrel until about 1926. It was 20" long on the H.