.357 Mag, 147gr smileys… wild spread numbers… crimp?

I picked up some of these to try for .357 mag, which I have never loaded before. There is very little load data for 147gr, so I sort of split the difference between 158 and 140 gr data.

Ramshot Enforcer, 14.0gr, and 14.5gr
1.590 OAL
CCI SP Mag primers
Mixed brass, but true once or twice fired
Chrono’d out of a Ruger GP100, 4.2″ barrel

Got wild spreads. Like 950fps to 1250fps over 30+ rounds. They averaged around 1100fps, which is about what I was expecting, but it was all over the place. I chrono’d other known ammo at the same time, and it was all normal. I also individually weighed all of the charges for these chrono batches, so it isn’t powder variation.

They felt fine, and seemed plenty accurate under 15 yards (indoor range). I did notice that one of the super low velocity ones (900-ish fps) had a much bigger flash than the others.

These bullets don’t have a cannelure, so I loaded them similar to my 9mm loads. I used a UniqueTek funnel/expander, which generally has really good neck tension, and I put a light taper crimp on them. I did the bench-push test, and I also measured the 6th round after firing five, and there is no setback at all.

I am thinking I need to try a deeper roll crimp, for more pressure consistency? I can’t imagine what else could cause such major velocity spread.

Any opinions are appreciated before I try the next batch. Thanks in advance.