[gunn5000]

is there any difference between 9 and 40 full size mags other than the round count holes/ markings? in other words, can i use 40 mags in a 9 with 9mm ammo and vice versa? i'm about to purchase a new 40 and plan on purchasing extra mags for it, just wondering if this is possible?

i've owned hk's for the better part of a decade but if this is a dumbass/ newb question, please, be gentle.:62:

 

[hkmanlp1]

They are not supposed to be interchangeable far as I know. Let me clarify, they have been known to work in the usp compacts. But not the full size usp. There is a reason the 40 mag says 40 and the 9mm mag says 9mm. That's my advice.

 

[USPc_4_life]

The feed lip gaps are different...the magazine springs are different...the followers are different...you get the point...

In the USPc some people have 'cross-platformed' for conversions (ie a .40 slide/barrel/spring on a 9mm frame or vice versa)
Some confusion also stems from the USPc .40 and 357 sig magazines being identical(they are) and interchangeable...this is of course because the .40 and .357sig are 'sisters'...9mm is small enough to physically fit inside a .40 shell

...stick with the right part for the right caliber...its safer and its built to last when used properly and makes you look a lot less inept

 

[TooSixy]

I hate to disappoint you guys, but the USP 9 and .40 mags are interchangeable. The round markings on the mag body, of course, are different (13 rds -vs- 15 rds), but the mags are the same. Down to the magazine spring, follower, and floor plates.

In addition, the Jet Funnel mags for 9mm and .40 are also identical. You can load 9mm rounds in .40 mags and vice versa. And they feed fine, too.

 

[OneShot]

I hate to disappoint you guys, but the USP 9 and .40 mags are interchangeable. The round markings on the mag body, of course, are different (13 rds -vs- 15 rds), but the mags are the same. Down to the magazine spring, follower, and floor plates.

In addition, the Jet Funnel mags for 9mm and .40 are also identical. You can load 9mm rounds in .40 mags and vice versa. And they feed fine, too.

Yes! Also, with the factory 31rd 9x19 magazine, you can load up to 27, IIRC, of .40s&w and it will also feed reliably.

 

[gunn5000]

certainly going to use/buy the correct magazines for each pistol, just want to have as complete a knowledge of each of my weapons and that would definitely include part interchangeability/reciprocity. thanks for the info, gentleman.

 

[USPc_4_life]

I remember another thread not long ago...guy was having feed issues on a USPf, during which we mic'd the feed lip gaps on 3 of my USPf magazines; I cannot for the life of me find it, however running through threads in the search bar, concensus is using 9mm in a .40 mag works okay-ish but .40 in a 9mm mag does not...meaning the feed lips are gapped differently (obviously)

I stand corrected on the mag spring/follower being different...thank you Toosixy...learn something new everyday!

Its still not a great idea to use the 'wrong' caliber in mismarked magazines...but as OP stated, it is more a curiosa than actual intent...

 

[Alex_6ix]

i have a few .40 mags that i just got, and they feed just as well as the 9mm mags. but the lips are slightly bigger on the .40