It's a fair question, basically VFC use the same buffer tube for the M27 as their M4 and HK416.
Basically the little lever you push to adjust the position of the stock is a pin that engages in a cutout along the bottom of the stock tube. If you push it in to adjust you need to pull it out the other way (so the pin pulls further down) Then you can slide the stock straight off the end. The MOE/CTR stocks (they are different - slightly) work the same way, pull down on the pin, slide the stock on and let go. Job jobbed.