[cowboy1964]

They're pretty close in size as far as I can tell. The 45 is about .25" longer so I'm assuming the 9 would probably fit a 45 holster but possibly not the other way around. I realize it may be dependent on the exact holster too. I'm specifically wondering about the MTAC.

 

[NEOH212]

The USPc 9/40 are on a smaller frame than the USPc .45. I know the holster manufactures have different stock numbers of the same holster for the 9/40 vs .45 versions.

It may fit but will probably be some what loose.

 

[G26S239]

I just tried my USPc 40 in my USPc 45 holster. It is not quite as tight as the 45 but it doesn't fall out when held upside down. The holster is a Don Hume H721 OWB style.

 

[RocPO]

Given that half the use of a holster is retention,I wouldn't cjeap out

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[BuckyP]

I have a Mitch Rosen holster for a .45 USPc, and my .40 fits securely in it. My P2000 fits as well. :dunno:

 

[FL_Hunter]

What NEO said.
The USPc 9mm and 40 are the same sized frame. The 45 is a bit larger. I would think that leather Holsters might Accommodate both sizes while polymer / kydex might not.
Just my 2c.