1. Magazines designed or manufactured for both rimfire calibre rifles and handguns
Magazines designed to contain rimfire cartridges and designed or manufactured for use in a rifle do not have a regulated capacity. However, magazines designed to contain rimfire cartridges and designed or manufactured for use in a semiautomatic handgun are limited to 10 cartridges. Magazines designed or manufactured for use in both rifles and semiautomatic handguns are subject to the handgun limit of 10 cartridges.
Example:
Smith & Wesson M&P 15-22 rifle and 15-22P pistol chambered for 22LR caliber:
the 10 round magazine is unregulated
the 25 round magazine is a prohibited device
Example 2*: The Ruger BX-25 magazine, chambered for 22 LR calibre, is designed and manufactured for use in the Ruger SR22 rifle, the 10/22 family of rifles/carbines and the 22 Charger handgun. As a result, this magazine is a prohibited device unless modified so its capacity is 10 cartridges or less. (*This information was not included in the original version of this bulletin, but was added on 2013-09-05.)
and then this archive says the aftermarket ones are designed for the rifle not pistol so they are ok. guess the RCMP has decided they are designed for both rifle and pistol to screw us over
The Smith & Wesson M&P15-22 can legally only hold 10 rounds as the magazine was originally designed for the M&P15-22 handgun. Even though it is a 22 rimfire rifle, the magazine was designed for use in a pistol and therefore is limited to 10 rounds.
The same goes for the factory Ruger 10/22 25 round magazines. These magazines are limited to 10 rounds as they are also for the Ruger Charger pistol. However, after market 10/22 mags such as the Butler Creek models have no such restriction placed on them, as they are not marketed as pistol magazines. This makes them legal to use in both rifles and the Charger pistol.