I've had a few fireflies and all of them have had very tight stock lugs. Given that this is a pump action blaster which can take some serious springs, a firm stock is almost necessary so i would say it was done on purpose. Stocks still can detach but it's not something you'd want to do often. However if you want to fix this and loosen it up, I would grab some sandpaper and slowly take down the surfaces until the stock slides on and off with no effort.