The cylinder latch and pawl work exactly the same, single or double action. At lockup only one side of the cylinder latch is in contact with the side of the notch in the cylinder. It doesn't get jammed tightly into the notch. The cylinder rotation presses the latch against the side of the notch and the other side of the latch is pressed against the side of the slot in the frame. This is how all Ruger revolvers work. It doesn't matter if the tip of the latch that goes into the cylinder notch is thick or thin. The lockup is caused by the thickness of the tip of the pawl. The thickness of the latch only determines the location of the cylinder at lockup.
This can be easily seen by looking at an UNLOADED Ruger revolver. Look at the right side of the gun at the rear of the cylinder. On double action guns slowly pull the trigger back, on single action guns slowly pull back the hammer. The tip of the pawl will move forward and up until it contacts the ratchet on the extractor. It will turn the cylinder as it slides along the angled face of the extractor ratchet. Then, as the hammer is almost all the way back, and the cylinder latch has snapped into the cylinder notch, the tip of the pawl comes to rest against a small flat surface on the extractor ratchet. At full cock, the right side of the pawl is pressing against the right side of the slot in the recoil shield. The left side of the pawl, at the tip, is pressing against the flat on the extractor ratchet. This puts rotational pressure on the cylinder. So one side of the cylinder notch is pressed against the latch. The other side of the latch is pressed against the side of the slot cut in the frame.
Take a look at your gun in the fired, trigger released condition. The cylinder should have some rotational play in it. Then put a little pressure on the cylinder so that the latch is pressed over tightly against the side of the slot in the bottom of the frame window. You can see that if you change the thickness of the tip of the latch, you will change the position of the cylinder when it is at lockup.
When I "blueprint" an SP101, the first thing I set is the barrel to cylinder bore alignment. When looking down the barrel, a thinner latch will move the bore of the cylinder to the right. A thicker latch will move the bore of the cylinder to the left. Vertical alignment is trickier because it involves work to the the crane and the crane pivot hole. But rarely is there a vertical alignment problem. After the alignment is perfect I re-fit a new pawl. If the tip is too thin, the lockup will be sloppy. If the tip is too thick it will bind when the trigger is pulled all the way back (on a single action it would bind at full cock).
Adjusting the timing (not to be confused with the alignment) is next. But I won't go into that here as we are only dealing with the "lockup".
Precise fitting of the latch and pawl requires removing metal .001 at a time using #400 grit paper and a surface plate. I used to buy my latches, pawls and trigger plungers 20 at a time. Not only is this process very time consuming, but the precise fitting of the parts makes it real handy to have plenty of spares on hand.
When you pay $400 to a custom gunsmith to build you a gun, it's not all for the glass bead finish and the new sights. Much of the cost is for the hand fitting of the parts. Way, way back in the old days, some production guns actually came from the factory hand fitted. But time is money. That's why you can't buy a new Colt Python anymore.
