I have a 15-4, square butt that shoots really great, but it is the most uncomfortable thing to shoot that I own. I dislike how the grip is real small to start with, and then it is real fat at the square end. It just doesn't fit.
I have seen photos of older guns with some kind of "filler piece" that turns the skinny part of the grip into something a man can hold onto. Are these "fillers" still made? Is there a different grip that fits the square butt K frame?
The fillers are still made. Tyler T-grip. There also used to be others by Pachmayr and S&W, but the Tylers are, in my opinion, the best.
Hogue makes excellent grips for the K-frame square-butt revolvers, Safariland used to, and Pachmayr still does. Which you find best will depend on your hand size.
This is a Tyler T adapter on my S&W #58. I didn't care for it and threw it away. A few folks inquired about it, and I dug it out of the garbage and sent it to the man who put me on this gun. I wiped it off first.