Hi. I just bought a new M9-A1 and found this forum while searching for mags. Lotsa good info here, especially the 1911 plunger spring trick.
Welcome to the club - I'm sure you will love your newly acquired M-A1 for years to come. Don't forget the obligatory range report.
Hey, don't get too crazy on the plunger spring thing.........you may not need that at all. Congrats on the new purchase. Just shoot it and break it in. And remember the range report..............