in 2013 the JG G36 was discontinued in USA due to to trademarks which Umarex have monopoly on THAT is why JG G36's & some others are not sold new by major US retailers In fact due to this US G36's are a lot more expensive as they have to sell licensed ones   https://www.airsoftsociety.com/threads/mk-g36s-discontinued.68179/   In the last few years JG have added a unique spring guide (no ball bearing) with a grub screw in it this basically can compress the s