Why do some people use premium gas in low compression engines?
Why do some people use low sodium soy sauce?
Why do some people order a Big Mac, large fries, and a diet coke?
Why do some people order Hawaiian pizza?
True, but most bullets for 9mm are .355/.356 where as most .38 bullets are .357/.358.
My 929 wouldn't shoot factory ammo very well. Poor accuracy and lots of failures to fire.
If you come home with two rounds left in your moons, that means the course designer did a good job of keeping it six round neutrall.
Some do some don't.
As I said, with a 7 round gun you're competing against 8-shot guns, not 6.
I've got both a 929 and a 627.
Both barrels slugged at .357. In my 627 I run a .358 160 Bayou Bullet in front of 3gr of Clays (not universal, not international) in a Starline .38 Short Colt case.
It took a while to get my 929 to run right. I finally settled on .358 147gr bullet. In a Federal case, with a .035 mom clip.
99.99% of the time I shoot my 627.