Hi, some musings on the LeMat cylinder lockup. The following photos show the back of the cylinder and LeMat bolt:
Notice the nine holes between the nipples, ~1/8" deep. The end of the bolt has a radius, the bolt diameter near the end of the bolt is 0.086". To determine the cylinder hole diameters I tried to insert different drills. A 0.086" would go into the holes, but a 0.088" drill would not enter the holes. This had me guess that the cylinder bolt holes are ~0.087".
Since the bolt diameter is smaller than the cylinder bolt holes, the bolt can completely enter the holes. The end of the bolt is radiused, the bolt fits like a pin in a socket. This is a very slick method of lockup, but has an issue. When the bolt drops, if it isn't perfectly aligned with the cylinder hole, it lightly peens the cylinder hole edge. This peened edge begins to narrow the cylinder holes. To again open the holes to the original size a reamer of 0.087" was purchased. The cylinder holes were then hand reamed. Based on how the reamer feels in the hole, I suspect that the actual hole diameter is closer to 0.0875". Is 0.0005" worth another $25 for the last 0.0005"? Probably not.
Since I now have a reamer, the holes will be optimized when the hole edges show peening. There seems to be a lot of latitude when adjusting when the bolt drops on hammer pull. Adjusting the small timing screw to have the bolt fall just as the cylinder bolt hole is aligned with the bolt will minimize peening since more of the hole edge takes the force of the bolt dropping. However, if performance timing is required (fast draw, etc.) the bolt should drop early accepting the added peening wear.
This is an example of trying to learn the engineering designed into our BP revolvers. I encourage others to also understand their revolver internal workings.
Regards,
Richard