With the follower removed, a proper spring will protrude from the top of the magazine as shown.
If you purchased an HKP30/VP9 magazine extension from us in November/December, take a minute to check your springs — the supplied spring may be defective.
Your HK springs should slide into the magazine easily, without dragging on the sidewalls. Depending on the exact shape of the top coil, without the follower attached, it should slide all the way up until it protrudes out the top of the magazine. (See photo.)
If you have a caliper handy, you can also check the width of the bottom coils. They should measure approximately .658 inches. The defective batch we’ve identified measures .720.
We don’t have an exact number on how many “bad” springs are in circulation, but we expect the number is less than 50. If you have a defective spring, please return it to us for immediate replacement!