How goes it gentlemen.  Quick question for you guys.  What's the best way ya'll have found to break in a new Glock magazine?  I bought a new 9rd for my 30 and I can't get the 9th one in there for anything.  I've kept the spring under tension for about a week now with 8rds and I was just messing with it again trying to get the last one in.  It won't quite make it.  I stuffed an empty on top of the 8 already in there as far down as I can get it hoping to put a little more tension on the spring to wear it down some more.  What do you guys think??  I appreciate the input.  

I had no problem getting my 9rd mag fully loaded... but I can open a can with out giving it over to my wife...

Force that pig in there, I found it helped to work the mag with 8rds loaded with the glock loader, and  use some force, after that it's still hard to load but I can fit the 9th round in there.
And it seats fully loaded, you just gotta press the mag in there.

To weaken the spring, you have to load and unload the magazine. When you leave it loaded, it won't get weaker. Something to do with the properties of steel. That's what arfcom tactical couch commandos have told me, anyway.

I could never get the last round into my G27 until I put a magazine extender on it.

thanks guys.  i'll keep messing with it.

Don't be afraid to force it.

It was a real pain in the ass to get 9rds at first, I had to work the mag like crazy with the mag loader with the mag base plate flat on a table with 8 rounds, then I managed to get the 9th in there
then I worked it hard with the mag loader, it's still a pain in the ass to load, but it can be done, and I have to really force the mag in the gun with the slide closed as I like to carry 9 + 1.

Good luck.

Leaving the mag loaded won't weaken the spring ... or in your case break it in. You will need to load and unload it repeatedly. Let me say this ... I just sold my G30 yesterday. I had it for 2 years and the mags were still really hard to load. I had 3 10 rd mags. Great pistil, I just in another direction ... a G38.

I break a sweat on the last round of my 9-rounders (all new). I even dent the cases a little sometimes. And after forcing the mag into the G30, I can barely rack the slide.

I've noticed that it seems to make a difference whether or not I hold the trigger to the rear while racking. My concern is that carrying 9+1, whether or not the slide will cycle after the first shot with my finger still holding the trigger to the rear. It does, but trying it manually shows that it is really tight.

I'm going to leave the 9-rounders sitting fully loaded for a few months. Some say it won't matter leaving the spring under tension compression, but at least I'm not tearing up my thumbs for the next few months.

I just picked up a bagful of used 10-rounders and can get #10 in there with reasonable effort.

G21 mags were never this much trouble.