Has anyone heard of this? I found a video on YouTube, some guy showed how to easily make a 17 round magazine for a Hellcat micro compact 9mm. I just bought a Hellcat, it came with an 11 round magazine and a 13 round magazine. I also just ordered a factory new 15 round magazine, so now I’ll have three mags of different sizes. Apparently you can disassemble the 13 round mag and 15 round mag, then use the 13 round spring and base plate on the 15 round mag and you’ll be able to get 17 rounds in the modified 15 round magazine. The guy showed how to do it then proceeded to shoot 17 rounds with zero malfunctions. Has anyone tried this? I’m wondering how reliable this would be, it would be interesting to make one of these and run about 1,000 rounds through it to see if there are any jams…
@HELLCAT To be on the safe side order another spare 13 and 15 rnd mags, and tinker with those just in case anything happens later on so you won’t be left magless. This way you’ll have your 11 rnd, 13 rnd, 15 rnd, and the tinkered 17 rnd mags.
This is the first time I heard of it… I don’t think I would trust this, I could see this resulting in FTF’s in my opinion.
Mine, too. Probably also Springfield, or they would ship 'em that way.
Without knowing details of the Hellcat mechanisms, my guesses are once the spring starts to soften a bit:
- will not lock on empty; later
- will occasionally misfeed in the final few rounds; eventually
- random feed malfunctions after the first few rounds.
If there’s a reason to make a range toy out of such a gun, sure — have a blast. I would not consider that mod for self defense. At least not until somebody designs and produces a credible aftermarket “power” spring intended to push 17 out of a 15. Probably not then, either.
Not sure why this would be a desirable thing, anyway. The first thing that makes a semi-auto hard to conceal is height, not length. The second thing is a heavy magazine trying to flop outward with only a short barrel trying to keep it tucked in. Hanging 17 rounds off a 3 inch barrel seems like custom build for a concealment failure — even if the FrankenMag did feed rounds.
Suggest running this past the Springfield forum.
That would be something I might use at the range. I doubt I would carry them.
If some guy on YouTube can do it maybe Springfield will come out with one done right from the factory. For EDC I’d stick with my 15 round factory mag, but 17 +1 rounds at the range would blow people away!
Sounds like a potentially OK range toy. But a 13 round spring in a 17 round mag seems likely to cause problems eventually. Wonder why you wouldn’t use the 15 round spring?
I think the scheme is that the shorter 13 round spring in a 15 round mag leaves room to squeeze an extra round or two into the 15 round mag.
If one can conceal a 15-17 round grip, I don’t know why not just carry an M&P9c or G19 designed for 15/17 — mature design lacks the “wildman” image, I suppose. 
Experimentation can lead to innovation, but YouTube following is not exactly rigorous investigation.
I could see the appeal of a slightly higher capacity spare mag for those that want to carry a more concealable firearm but want more rounds available in case they are needed. But don’t want to turn this into another how many rounds do you carry thread;)
Most double stack Glock mags seem to function pretty well with the standard spring and a +2 baseplate. So I guess this is a similar conversion though +4 rounds is stretching things twice as far as +2.
Zero chance I would ever consider this given the possibility of sacrificing reliability for a few more rounds. If 14 rounds or even 16 rounds in the gun isn’t enough (seems pretty unlikely it wouldn’t be)…carry a bigger gun that is designed to hold that many rounds with an OEM magazine. Lots of choices out there.