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[shooterx10]

for use in IDPA or USPSA classifiers

Other than sticking it to the man, the only reason a shooter would do this is for shooting IDPA or USPSA classifiers so you don't have to reload or swap your 10 round mags and hold up everyone behind you. Not to mention, this will make the Range Officers impatient! For a classifier, you shoot several strings at the same targets.

However, I think in the USPSA, production guns are loaded only to 10 rounds, so having the 10 round 40 mags loaded with more than 10 9mm rounds is kind of a moot point. This goes true as well for guns used in IDPA.

[MilSpec.45]

You can put 15 rounds of 9mm in a XD40 10 round mag and use it in your XD9 with little or no problems.

As far as I can tell, it is not illegal.

[jfcosgrove3]

Legality

It is legal to load mags with different ammunition. It is not legal at any time to have more than 10 rounds in a magazine no matter what modifications are done to the magazine, unless you are law enforcement.

[zenthemighty]

It is legal to load mags with different ammunition. It is not legal at any time to have more than 10 rounds in a magazine no matter what modifications are done to the magazine, unless you are law enforcement.

Oh please. Show me the reg that says that. What if I owned the mag prior to 2000?

[glockk9mm]

Same with Bertta 96 mags in the 92. My understanding is that it was perfectly legal.

I know my beretta mags accept 14 9mm rounds, as far as how reliable it would feed through the 92, I dont know I havent fired the 92 with the 96 mags in fear that I'll get questioned by off duty cops at the range on how I obtained hicap mags.

[avidone]

It is legal to load mags with different ammunition. It is not legal at any time to have more than 10 rounds in a magazine no matter what modifications are done to the magazine, unless you are law enforcement.

That's not true. If you have high capacity magazines that were legally aquired before they were banned in CA, there are no restrictions on posession and use unless you were to create an AW by configuation.

[wutzu]

It is legal to load mags with different ammunition. It is not legal at any time to have more than 10 rounds in a magazine no matter what modifications are done to the magazine, unless you are law enforcement.

Have you even read the law?