That is interesting you say that as I accidentally ground my bolt on my NMA too narrow. I was prepared to order a new one but it shoots and cycles great now! It has a little rotational shake but doesn't seem to matter much. The chamber to bore alignment is much better now also. Before it was off to one side.
Well, line bored custom and semi custom made guns (not talking about tuned up guns ) will have a lock up with virtually no lateral movement and they will pretty much stay that way. These guns are capable of minute of angle ( one inch at 100 yards) over a bench with all the chambers used in the same group.
I admit some makers of custom revolvers do get it right but we are talking factory guns that need some cylinder play. I will not mention the maker of the one I mentioned but the price was steep. It seems it was not line bored as the original cylinder was used, just all play removed to the detriment of accuracy.
Did it spit lead? It's important to keep the inside corners of both forcing cone and chamber mouths a sharp profile with a slight braking to remove burrs, to discourage gas cutting.
The route I took with my 58 Pietta was to remove the barrel and made a reaming fixture that fit the major thread diameter of the receiver/solid frame, barrel hole threads, with a very tight interference fit ( no wiggle). This fixture guided the reamer into the existing chambers with the cylinder left in the frame and held by the bolt in the gun. Light cutting was the order of the day and metal removal in each chamber was being guided by the lock up of each chamber in the existing gun. I was getting a clean thin cut of fresh steel from all sides of each chamber so knew the reamer was well centered. A check with a plug gauge that would just fit down bore and into each chamber after the barrel was reinstalled confirmed excellent alignment.
A point I alluded to earlier is shooting a group with all the cylinders chambers as opposed to what is occasionally done in that a person will find one or more chambers have better accuracy than the rest (common with factory guns) and shoot a group using only the most accurate ones. This is because of inconsistent barrel/chamber alignment or depth in most instances. A loose bolt/notch/window fit that allows increased random lock up positioning would not be as accurate as tight consistent fit that launches the projectile be it ball or bullet aligned with barrel bore, the same way each time.
Many won't do that at 25 yards from a Ransom Rest let alone 200 yards from sand bags I presume ! Sensational shooting indeed! Was this using all the chambers ?
