the limit is a store thing not corporate it seems. A couple semi local stores to me had no signs and let me buy 10-20 cci Sv at a time
I picked up 300 CCI Mini Mags at my local Walmart tonight. The guy with the ammo cabinet key didn't know there was a 3 box limit (there's no signage on the cabinet either). Unfortunately there was another employee (maybe a supervisor) at the counter when he was going to ring me up for 5 boxes (all they had). He informed the kid with the key that there was a 3 box limit.
Darn my luck. What are the odds of having 2 Walmart employees at the sporting goods desk at once? 3 boxes came out to $25.10 with tax - .084 per round.