Ordered a new 10/22 magazine spring and plunger from Kidd Innovative Design. They were shipped lightning freaking fast. Seems like I just hung up the phone.

Got it today, installed it today. Used the stiffer of 2 springs.

Easy to install, and so far the magazine retention in the world's crudest registered SBR seems a lot better. $19.50 for the slightly longer plunger, 2 springs of standard and heavier weight, a set of oversimplified instructions, plus $4 for the surreally rapid shipping.

Hope to shoot Sunday, so I can test whether it does what I want.