Just curious if anyone else has experienced this.

So Saturday me and the missus went shooting, and I brought my .327 SP101 to shoot for the 1st time.  Put 80 rounds of .32H&R Mag through it, shot great, accurate, perfect holes in the paper.  Put 50 .327 Fed. Mag. through it, same result (though a lot more noise and recoil than I expected.)  Then I started shooting some S&B 100 grain wadcutters in .32S&W Long through it.....and they were all keyholing.  I put another dozen H&Rs through it, and they all worked fine, but the S&B wadcutters kept keyholing.  All the H&R and .327 ammo was 85 grain, and I've shot the S&B wadcutters through a Smith 31 without an issue in the past (though I can't swear to them being 100 grains in the past.)  I will say that the .32S&W felt like shooting an air pistol, less felt recoil than I feel shooting .22lr out of a revolver.

Any ideas?

Too long of a jump from the end of the cartridge case to the chamber mouth in the cylinder?
If this distance is longer than the bullet, the bullet is unsupported and is in free flight inside the chamber. Unless the bullet hits exactly dead center in the chamber mouth it will tip and get ruined as it goes through the chamber mouth and then crosses the cylinder gap and hits the forcing cone.

Gar, hadn't thought of that.  The S&W 31 is of course designed for .32S&W, but I guess the notion of firing it through the .327 might be iffy with the longer cylinder.  I didn't see any noticeable leading around the forcing cone, but I only fired 18 .32s total after seeing the keyholing.  Reckon I might try some LRN .32s out of it next range trip just to see if they work right.  I guess I will relegate the wadcutters to the Model 31.

It will be a bummer if the LRNs keyhole though, as one of the purposes of the SP101 was to be a durable knock around revolver that would serve me into older age with the .32S&Ws when I get recoil averse enough.  (I bought it after retiring earlier this year.)  I viewed it as a less labor intensive alternative the the S&W 31 with its bright blueing.

Are you using .32 S&W? Or .32 S&W Long? The .32 S&W is very short and while it does work, there is way too much length in a .327 Fed Mag cylinder. I have the same one and the Taurus 327 as well. I have fired .327, .32 H&R Mag and .32 S&W Long with no issues but I have never felt the need to shoot .32 S&W. Its much harder to find so I just keep a stash for my S&W Model 1 1/2.

Edit: Just re-read and saw in the OP you said wad Cutter in .32 S&W Long. Maybe it is a combination of the longer cylinder and a flat nose not feeding straight.

If you’re too old for the recoil, you probably won’t be able to pull the trigger anyway.