I am looking for a semi-auto that is thin so it will fit my wife's hand. It is ok if it normally holds 7 rds but when we go to the range she wants a mag the holds 12 or more rounds so she does not have to reload the mag as often. Is there a slim compact handgun that will accept a different capacity magazine?

ETS is making large G43 magazines.

ETS 12 rd G43 mag

S&W Shield 9mm has both 7 & 8 rds mags. Add a MagGuts +2 conversion to the 8rd and you have a 10rd mag.
HTH...

Tomac

Read my mind.

Buddy of mine his magguts stopped feeding properly the spring did not hold tension very well.  He went back to the stock springs because it was not very reliable after a bit of use.

Glock 26. It is not that thin but my wife has small hands and she likes hers.

And it can use 17 round mags (or more).

If you're considering a single stack, the only real answer is buy several extra magazines.  My wife's two main handguns are the Ruger SR9c and the LC9.  She enjoys shooting the double stack more at the range and most of her training classes, but she does her CCW training and carry mostly with the LC9.  I just said screw it and she has about a dozen magazines.  We load up before hitting the range and she has several mag changes to keep focus on the training.  My son selected and XDs 9mm, which is another nice, slim carry gun.  I loaded him up with a variety of 7, 8, and 9 round magazines.  He likes the 8 round mags the best, but he appreciates that 9 round mag as a carried reload magazine.  My shield 9mm is pretty thin, but only with 7 or 8 round magazines; I know ProMag has some 10 round mags, but I don't have any nor would I trust them.

I'll give a plug for Ruger's SR9c. I wasn't really interested until my wife put hands on it and fell in love.  It's one of the slimmer double stack handguns and she really likes how it feels in her hand.  Although it does have a standard 10 round magazine, it takes the larger 17round magazines as well.  Most of her CCW drills are with 5 or 6 round loaded magazines...just more frequent magazine changes.  She still has about a dozen different 10 and 17 round magazines which all get loaded before a class or hitting the range for informal training.

The SR9c is slightly more thinner in the grip than my slimmest double stack 9mm, the HK P2000K, which is another option.  It has standard 10 round magazines and will take 13 round extended magazines.

Here, I just snapped a couple quick pictures (Shield 9mm w/ 8rd mag; XDs 9mm with 9rd mag; SR9c w/ 17rd mag; HK P2K w/ 13rd mag; and Glock 26 w/ 12rd Magpul mag)







I didn't consider my Sig sub-compacts, the P938 or P290RS.  The P290RS is another great little gun that has an 8 round magazine...

ROCK6

Had the same questions a few years back when wife was getting COW. She picked the M&P 9C. I was happy because I have a 9 Pro. She keeps a few of my mags with grip adapter in center console.

HK P2000 and uspc

P30 and VP9 IIRC

Ruger has a 9 round extended magazine for their LC9 and LC9s handguns.

I feel slim compact guns are a great choice and for carry should be carried with flush fit mags, my feeling being if you are going to add bulk to your small gun why not just start with a bigger one!?
absolutely have a minimum of three spare mags and my answer is load them all the day before you plan to go to the range.
I am dead against mag extensions for the reason cited above plus there are more than a few posts about a gun becoming unreliable when used.
Plus compared to when carrying with the flush magazine some guns handling character changes with the longer mags in place
Make a long term commitment to a single stack carry gun you trust and support that with a couple hundred bucks spent on spare mags

Thanks everyone for your reply and effort to help. I was thinking the Shield or Glock was the best choice to solve my question so this did help.

The Glock 26 is the gold standard for a small gun that can accept extended magazines. It really isn't that thin when compared to single stack guns, but it isn't that bad. With Glocks, there is a shelf on both the magazine and inside the mag well in the frame that interact and make overinserting the magazine impossible and a grip adapter on the magazine isn't necessary. You can put one on the magazine if it makes it more comfortable but it isn't necessary for function. A VERY good design choice on Glock's part and I wish every manufacturer would do that.

My wife has a Ruger SR9C. Pretty nice gun and is nice and thin for a double stack gun. It is also fairly compact with the 10 rd magazine inserted. It can take 17 rd magazines from the full sized SR9, but a grip adapter is necessary to prevent overinserting the magazine and possibly damaging the gun. She has had some problems with light primer strikes in her gun, but they seem to be getting less frequent as she shoots it more, so we're waiting to see if the gun "wears in" before sending it back. While not a common problem, from doing some reading, it seems that light primer strikes on the SR series isn't unheard of, so be aware of that and make sure you shoot the gun a bit before relying on it, if you decide to go that way.

For the single stack guns, the only real option for extended magazines is the Glock 42 and 43. ETS makes aftermarket extended magazines for both, 9 and 12 rd capacity IIRC. Aside from magazine follower and spring combos for some other guns (like MagGuts spring/follower combos), that's about your only real option for extended mags for single stack guns that I know of.

While I understand the desire to spend range time shooting instead of reloading magazines, if your wife is going to be carrying a small single stack gun, she really needs to be practicing with the small magazines she would be carrying. On the small guns with extended magazines, the feel can change quite a bit, namely making it easier to shoot than with the smaller mags. I'd think it would be better to practice with the smaller mags to make sure you can shoot the gun as it would be carried, with the smaller mags. Of course, as long as you have a wife wanting to shoot, you have a winner and you should encourage that. Just my $0.02 worth, take it for what it's worth and don't discourage her from shooting. Good luck.

Bub75