Don't don't what your experience has been but for what it's worth when I reloaded for my AR-15 I used regular WSR when I couldn't find CCI 400's and never had a slam fire. That said, probably never fired more than a box of WSR (1000 rounds).
In Alberta try The Shooting edge (sponser) picked up a case (5k) there a few weeks ago
CCI 400's are standard primers, CCI 450's are Magnums."...CCI #400 small rifle primer..." They're magnum primers. Magnum primers don't use a different cup. CCI "milspec" primers are a marketing gimmick for magnum primers.
Here is his EE ad that has 5000 CCI Small Rifle Primers
http://www.canadiangunnutz.com/forum/showthread.php?t=402990
CCI's are $23/k, Federals are $30/k where I buy my supplies...
due tell then...