I thought I would add something here. I removed a K-frame locking bolt for bluing, and couldn't get the bolt to go back in. I could push it in with great pressure but the front part would stop at the front hole. After reading this thread, I measured the diameter of the bolt at front and rear and there was only 0.002" difference. After some head scratching, I decided that in getting the pin out I had created a burr on the inside of the locking bolt cylinder. I took some 1000 grit sandpaper and rolled it up small enough to get into the cylinder and spun it around by hand and forward and backward. This did the trick and I was able to get the bolt to go in freely. I replaced the cylinder to hold the bolt in the proper position and drove the pin in and all is well.