Jamming 357 Sig

I reload my 357Sig and recently ran into a problem. 5-6 rounds out of 100 will jam after being fired in the gun (M&P). After reloading, I drop test them in the barrel and they all passed the test, some were a bit sticky but not bad. I marked them. Only one of the jammed in the pistol. By jam, I mean jammed in the barrel to the point I had to set the sight against the edge of a board or table and smack the grip to get it to unlock the slide. Bad ju ju..

Any suggestions? I am trying to find a carbide 40 cal die to presize the cases but all is "backorder or out of stock".
(Any one have one for sale let me know.)

I'm still an amateur, but 3 possibilities come to mind:

- Cases need trimming
- Sizing die needs adjustment
- Loading is too hot

Thanks. THe loads are not too hot as I never load to or above max. They may need to be trimmed.

357 sig can be difficult to get a good grip on the bullet.
Do you crimp them? Rounds lower in the magazine will start
working loose and moving forward during recoil. These will
then jam into the rifling and stop your gun.

They definitely must be crimped. Next, for sizing, the sizing die needs to just barely touch your shellholder, so that the case is as far into the sizing die as it can be. The shoulder has to be set back properly in 357 SIG to make it function.