I bought some of the Beretta ones for my 15 round APX magazines and they still only hold 15 rounds. There’s no way I could get a 16th round in them let alone 17.

The Beretta website says they’re compatible with all full size magazines.

Anyone else run into this problem?

I have no first hand experience with those extensions, but it would appear that various magazines of various brands, sometimes need a little break in before they load their full capacity.

In similar cases, people have talked about loading the mag and letting it sit for a certain period of time, or simply running the mag at downloaded capacity for a few sessions.

Also, did you change to a capacity appropriate spring?

Beretta doesn’t make any mention of having to use different springs nor is one included in the package with the extension, by all accounts the factory spring is what you’re supposed to use.

I have the mags sitting and loaded to 15 but I’m dubious any amount of compression that would still allow the springs to function is going to make a difference. It almost seems harder to get 15 in the mags now then it did with the original floor plates.

I have an email out to Beretta so we’ll see what they have to say.

Worst case scenario I’ll try clipping the springs bit by bit to see if I can find a length that will let me get the extra two rounds in there but still have enough force to feed reliably I guess.

That sounds tricky. Definitely give Beretta the lowdown on what you experienced, but it may still be prudent to inquire about springs, as it seems to be a general rule that longer mags require longer springs, which may or may not be the case here.

More than likely the OP didn't reinstall the mag spring correctly. The +2 extention adds more space to the end of the magazine, so there is no other logical reason why the factory mag is excepting the same capacity even with the +2 installed.

I'm in Colorado also. If your APX is full sized, (and 9mm) the 15rd mag is a restricted 17 rd mag so adding an extended floor plate can't add capacity. it only serves to add space for the spring.

If you have a .40, ignore the above.

The full-size APX magazines are 17 round mags. The reduced capacity 15 and 10 round mags have a blocker stamped into them so they can't accept more.

OP you'll need the 17 round mags for the extensions to work.