Air Canada is down by Delta (near the Crown Room Club, rather than by CO and the Presidents Club, but in the same pier for security.

There's a shuttle between Gates 35-45 (US) and Gates 23-34.. (AA/UA/US). There not an airside shuttle between those gates and gates 10-22.

So the OP will need to go landside and re-clear security.

That said, there's usually no more than a 5 minute wait at security. Very occasionally I've faced longer wait times... the Friday morning of Memorial Day Weekend a couple years back I had a 45 minute wait and no F line... and a few times I hit 10 minute lines. But really not longer. Key question is WHAT TIME ARE THE OP'S FLIGHTS (what time will he be transiting DCA)?

Bottom-line is that DCA is not a bad airport, even having to re-clear security. Whether 50 minutes works or doesn't work depends mostly on whether the inbound flight is on time. If it is I highly doubt there'll be any problems at all.