Anything i've seen from Walmart/Canadian Tire is pretty nasty as far as BBs go. In other words i recommend avoiding walmart/Canadian Tire altogether.
You want a brand of BB with a high polish and tight tolerances, even if it doesn't turn out to be the problem, it'll help keep your gun running smoothly anyway.
Here's a couple brands that you can't really go wrong with.
*BB Bastard* http://www.bbbastard.com/index.php They also make the only Bio BB i'd put in my gun. They are also my personal fav, and currently the only Brand of BB i run. You'll find most people on ASC are the same.
*Armist* http://www.surplusig.com/19/70/Gas_and_Ammunition.html Feature a double polish much like the BB Bastard brand. I've never used them, but i've heard nothing but good about them.
There are also other Brands like,
Madbull
Metal Tech
These should also be good, i have not used them but others have to great effect.
That L96 shoots really fast, according to it's spec sheet, you really should be using a heavy weight BB with it. I'd say nothing less then a 0.30g BB. Maybe even a 0.36 would be best. Have you chronied it yet?
A heavier BB will hold it's energy longer, thus more range usually. It'll also offer more resistance to wind and leaves, etc. Providing a more stable flight, and better accuracy.
Hope that helps.