MEC 330 Primer Seating Spring for 600 Jr / Mark 5 / Sizemaster / Steelmaster

The MEC #330 Primer Seating Spring is a genuine factory replacement spring used in the primer seating assembly on MEC single-stage shotshell reloading presses. This small but critical coil spring provides the tension that drives the primer cup forward to seat primers uniformly into fresh shells, and it is one of the most commonly replaced wear items on a workhorse MEC press.

MEC part #330 is built to fit the primer seat assembly on a wide range of MEC single-stage reloaders, including the 600 Jr. (both Pre-1982 and 1982-1985 production), the Mark 5, Sizemaster, Steelmaster, and the 700 Versamec (Pre-1982 and 1982-1985). It works together with MEC primer cup #326 and primer seating pad #331 to make up the complete primer seat assembly for these presses.

If your finished shells are showing inconsistent primer seating depth, primer push-backs, or your primer cup is not returning crisply between cycles, the seating spring is the usual culprit. Swapping in a fresh MEC #330 spring is a quick, inexpensive fix that restores positive primer seating on your existing press without replacing the whole machine.

Made in the USA by MEC, this is an OEM replacement part sold individually as a single spring.