Hi:
How much differences in frame size between a S&W Model 19-4 and a Colt Python?
My reason is I have a chance to purchase a holster made for a Colt Python
w/2.5" barrel. Will this holster fit a S&W Model 19-4 w/2.5" barrel?

Thanks,
Jimmy

Depends on how and if there is a strap. If it is fitted, it likely won't work too well. The 19 will be loose.

__________________
Lost it all in a boat accident

I've fit 4" K-frames in Python holsters several times. A thumb-strap will (usually) work but a thumb-break sometimes will and sometimes won't. The other way around is less likely

I think an L-frame would be a better fit in a Python holster.

Yeah, a Python holster will be a little too big for a K-frame.

The same holster is often marketed for the Python and other Colt .357's, the S&W L-frames, and the Ruger GP-100.

My GP-100 is worn in a Bianchi holster that I think is marked for MED REV. I used that same holster when I owned a M-686.

Andy said it right. I believe the Model 19 might be bumping around a little in a Colt Python holster.

I agree an L- frame is just right.

I tried my 2 1/2" Python in a 2 1/2" Galco K-frame holster.

The fit was somewhat tight and snug. The biggest difference was the positioning of the rear sight. The Python rear sight sits more forward than the K-frame S&W sight and the cut of the holster made it difficult to properly holster the Python because of the rear sight. I don't know if that would be an issue the other way around.

Remember too, the Colt has a significantly larger diameter cylinder than the S&W "K" frame.

A "K" frame in a Colt Python holster is going to be pretty loose.
A Colt in a "K" frame holster will stretch out and ruin the holster for use with the "K" frame again.