I acquired a Sig P320 in a tade. It came with two, what I assume to be, originally magazines. 17rd, grey follower, round peg in the bottom. I also bought one new production magazine locally, square peg in the baseplate. First day at the range, several failures to hold open after last shot out of one of the original magazines. All rounds fed flawlessly, however. Never tested the second as it was loaded with defense ammunition. The new magazine had no problem. So, must be a spring issue. I order two new springs from Ebay. I compared the two new Ebay springs to the original springs in the two older magazines that came with the gun, and to the spring in the new production magazines I bought locally.

New Ebay spring next to old spring and follower:


New Ebay spring next to both old magazine springs:


New production locally purchased magazine spring/follower next to old production:


Obviously quite a difference. Do you think the springs took that much of a set if kept loaded? Guy I acquired it from said he had 50rds through it, and the condition of the gun suggests he didn't WAY underestimate it. Or, did Sig make a change in magazine spring length to combat an issue simiilar to what I experienced in later production models? Maybe my mags found there way into having lower capacity springs in them?

Hard to tell, but I was shocked at the difference in length.

The new springs look to have an extra coil. Could be  +10% spring...

I count 12 on all springs prsetn. Ebay springs were advertised as being manufactured to factory spec. The spring from the new factory Sig mag is also much longer. I do not believe them to be a plus power spring.