As far as mags and rubber knives go, you shouldn't have a problem. The CBSA can detain anything they want though. But those items are not controlled.
As far as your pistol goes. They may write you a letter telling you it's detained. You then have the opportunity to write back explaining what it is, what you plan to do with it, why you should have it, ...ect. If denied "which is most likely" they will destroy it, and your money I'd gone. Trying to bring in airsoft guns into the country yourself is a bad idea.
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