Looking to pick one up soon. No shop in my area actually has one so I have to order it. How much longer is the grip than a 9c? from pictures it seems to be g19 sized.

They are g19 sized. I used to have one. I have shot a 40c as well and though I can't give any exact dimensions, the 45c is a little bigger.

Edit: The smith website shows that the overall height for the 45c over the 40c/9c is 4.8 vs 4.3 inches. I would assume that the difference is in the grip since I actually carried mine in a 9/40 holster.

A good choice! I love my 45c. I'm glad I got the compact version. I have pretty big hands and I don't find it to be too small at all.

The M&P45C is a nice size. The Glock 30 is thicker and pinches my finger between the gun and mag, but it does hold 2 additional rounds.

The 45c is comparable in size to the Glock 19, but is slightly thicker.

I took some comparison shots with my M&P9 full size, Glock 19, and M&P45 compact.

In the 1st and 2nd images, the order is M&P9FS, G19, 45c.

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M&Ps: 45, 45c, 9

For a Glock 30, try a 9 round magazine instead of the 10 round and see what you think. They should be readily available now. I use the 9 round in my 30S in order to get the piece a touch shorter in overall height. With the 10 round inserted it measures 4.8" and with the 9 round it is 4.5".

With the 9rd magazine my pinky goes under the magazine when I grip it so no pinch. Very similar to where my pinky goes when gripping the 9c & 40c.

As far as pinching goes if you want to continue using your 10 round magazine you might need to adjust your grip to get your pinky away from that gap or you might want to try like I did and using a small grit sander I removed some of that "shelf" material from the top of the mag plate to open up that pinching area a bit. That might work for you, too. I continue to use a 10 round magazine, but carry that or a 13 round as a spare instead of holstered.

I would have liked to have held/tried a 45C when I was in the market for a 45 double stack for carry, but at that time they were very rare and not available in my area.

I stumbled upon a 45c in my LGS and bought it the next day. He had 4 in stock that first day and when I went back they were all gone except the one I had put a deposit on. Haven't seen any since.
I've got the 9c, 40c and the 45c and really don't notice any significant difference in how they feel in my hand.