Will a model 1955 barrel work on a 1917

Yes, with proper fitting, as any new barrel.

Thanks, didn't know if cylinder was same length so barrel would meet cylinder when screwed in.

The barrel will thread in and should be about the right length, will probably need adjusted to get the gap right. But, the 1917 has a rounded frame where the barrel meets it, the 1955 barrel has a rib that will stick well above the frame. The 1955 front sight will be way high and the top of it may need lowered down to near the top of or into the ramp area. Either that or add adjust sights to 1917, Without some mods to frame or barrel its going to be a miss match. Oh and the large knob on end of 1917 ejector rod, eith that needs machined off or replaced, or the area it goes into on the shroud needs modified for clearance and the far side will end up with an opening. But it is possible to make it work. Here is a 1917 with a shortened 1950 barrel.

Thanks for the great info, knew it wouldn't match right up but barrels are so hard to find that you have to take what you can get. Can ejector rod be changed out as I didn't know how to separate it from the yoke.