HK USP 40 and 35740 and Compact magazines

[hksw]

Wanting to purchase additional magazines for my USP 9 Compact and USP 45 Compact I went 'net shopping. First place was, of course, CDNN. Upon landing on their page for HK Pistol Magazines,

http://www.cdnninvestments.com/hk2.html

I had noticed that the prices for the USP 40 and USP 357 Compacts were not the same. Both with finger extensions, the .357SIG mag is $6 more than the .40SW. Is there a difference between the two magazines? If so, what are they? (Other than the caliber stamped on the sides.) All of the other .40SW/.357SIG gun manufacturers that I have seen use the same mag for both calibers. (Yeah, yeah, Astra actually also uses the same mag for their A-75 in 9mm and .40SW.)

Also, will the USP 40 Compact mag fit into the USP 9 Compact?

Thanks in advanced.

 

[10-Ring]

Easy questions first...YES, the 40 mag will fit in the 9. I have been using them since the summer.
As for the difference between the 357 & 40 mags. Floor plates are the same, springs are the same, locking plate is the same, followers are the same. The difference is in the mag body.
This might explain why the conversion from compact 357 to 40 works & doesn't work in the fullsize USP since there are no 357 sig mags available. :banghead:

 

[hksw]

Ah, I see. Thanks 10.