Yes that stock folds and extends, its really nice. Fits the tippman adapter very snug too so its not shifting around when i try to shoot like some cheaper tippman stocks.
That is a 2240 hipac with the 4" extension, i get about 40 good shots per fill, i can go through 50, but the 50th shot is moving about 300fps
As for the adapter, i got it from SD custom design in the UK, it looks JUST like the Mellon, and very well could be one, but im not positive. I opted to order from SD as he had some other things i wanted, and NO wait. The Mellon wait list right now is quite painful if youre looking to get a gun ready and go shootin'
Thanks for the comment.