Close but a little bit off. In the semi auto divisions you are not limited to 10 rd mags. The IPSC rules state no limit. The IPSC rule exemptions express a 10 rd limit for pistol divisions (except the classic and revolver) so you can't use a 40 mag in a 9 and jam2 more rounds in etc. This is however a pistol rule exemption and has no weight on rifle divisions. So you think a 10rd Lar or ATRS mag is the best you can do. Not quite. A .50 Beowulf mag will hold 15 rds of 223 and the current IPSC international rules, IPSC Canada rule exemptions, and the Canadian firearms act and regulations... can't stop you. Oh of course the match director, CRO's, etc will rave on and on of how you can't but just ask them to prove it.
Moe