Cleared by US customs, but not by CBSA? Is that what you are saying?
Been there - less than a month ago.
You need to find out where it is and what its status is. If it's been cleared by Canada customs they may be waiting on a carrier.... in which case you might have to make pick-up arrangements.
If it is under $3000 (or so, I forget the exact figure) Canada Post should handle the brokerage (at least they say they do), if it is declared as over that magic number - you may need to get a broker to clear it for you.
Whatever you do .. ACT FAST! CBSA does not let stuff sit around, something like 30/45 some odd days and it is "forfeited to the crown" and destroyed. (doesn't matter if its a gun part or a bag of marbles. they do not care)
Something very odd has happened recently with anything gun-related at the CBSA ... everything is getting held up, a couple of my US suppliers will no longer ship to Canada. There is a very clear and boldly worded document on the import/export info site regarding the OIC as well.
good luck!