Dillon 650 357mag troubles. I need help from someone knowlegable. squibs

[HBARleatherneck]

I have been loading .357 magnum on my 650 for 2 years. I load 400-500 rounds of 357 on it every month . I never had 1 issue until last month.

starline 357 mag brass
3.1 grains unique powder (same 8# jug for more than year)
winchester WSP primers (clearly different lots by now, but same primer)

About a month or so ago, my son started shooting .38 at competitions, so I changed up my toolhead, but then just switched it all back and bought a whole other toolhead for him. Then switched him to 357 anyway.
So, the dies and powder measure were moved.
I have polished the powder measure to glistening. The powder bars are polished. Im using the standard small powder bar. Im using a powder check die.

I am having squibs. I weighed by hand close to 150 rounds out of the last 400 loaded and they were all perfect as far as weight. I get to the shoot today and have 4 squibs.

I have done everything I know to do. If you have any ideas let me know. Today I have to load 300 rounds for tomorrow. Im going to switch to Red dot 3.1 grains again, brand new starline brass and I will open a new box of primers.
The primers have good dents, the rounds are clearly entering the barrel, but powder charges must not be consistant.
Any idea if there is a possiblity of something on the powder measure? HELP!!!!

[Great-Kazoo]

Tighter crimp. Had the same issue with a 158 XTP, spoke with hornady the tech said they do a tighter crimp to avoid issues such as i had. Which sounds like you're experiencing.

[HBARleatherneck]

Ok Jim will see what happens tomorrow. Out of about 480 rounds over the last couple weeks I have had around 6 squibs, 4 of them today. When its that inconsistant its hard to pinpoint. I did tighten the crimp a bit on the 300 I just loaded since I talked to you.

I ran the cases from the case feeder all the way to the seating die, pulled the case and weighed all 300 cases by hand. There was never more than .2 grain variable. There is no way that was my problem. I hope the crimp adjustment is it.

[earplug]

Curious what bullet weight your using? Crimp sounds like the easy cure.

[thedave1164]

I have read about that problem on some other forums, and Jim is right the crimp is very important on some loads.

[earplug]

I'm betting the crimp will help. Did some reading on your load and its not listed online where I can find it. Have read that light loads of Unique don't burn very clean or evenly. Probably doesn't generate enough pressure to burn cleanly in the large case with the light bullet. A faster powder such as Red Dot might work better with such a large case and light bullet.