If your competing in the Production or Limited-10 class then I believe magazines are limited to 10 rounds. Limited and Unlimited do not limit the number of rounds but the length of the magazine.
I shot my first IPSC last week. Given the Unlimited guns I saw I don't think the XD's are going to be in that class very often. I did see one Unlimited Glock, it was very ugly. I will probably stay in Production or possible move up to Limited-10 to take advantage of the major classification of my 40S&W XD. Good luck and have fun.
You can always shoot the XD in Limited-10, but you can use up to 140mm magazines in Limited. I've thought about this some, and if I were going to set up an XD for limited, I'd probably see about making some magazines for it.
There are Beretta 9mm magazines that will fit the XD. Cut one off at 140mm, find a good spring and follower, and stretch the feed lips a little bit to feed .40 S&W. In theory, it should work. One of these days I'll try it.
I think the XD would make a really nice Limited gun with some higher capacity mags. There are a bunch of Glock shooters in Limited. He can just shoot Limited 10 with me until somebody starts making some mags for Limited. I am even thinking about getting myself an XD as a Limited gun if someone comes out with mags for it.
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