I have been running Dillon 650s, 550s and even a Square Deal B for a while and never had a primer blowout. I know people who have done it and it's pretty scary. The cause is always operator error and with my 650s I have to periodically take the priming system apart, especially the wheel and clean away all the crud. Once clean, reassemble but don't lube with anything other than a bit of dry lube. Lube will just trap dirt in the system.

Dillon will send you parts and you need to do some serious thought as to how you made it happen.

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Bob.
SWCA 1821