So glad I found this thread. Just got my M4 11707, and ran into the 4 shell load issue. Short of pulling the spring, couldn’t figure it out. Needless to say for the price of the gun, and having this issue when advertising 5+1 is slightly frustrating. The potential 7 spring isn’t bad if going to the full tube, but wasn’t something I planned on immediately, especially with 922 compliance (overall cost) from the initial cost of the gun.
Funny thing is the freedom fighter tactical video that covers the full Tube and 922r - dude says that people have run the 5 inch spring without issue. That was a flag to me, just on math and spring pressure. Now it makes sense if there is a 7 inch spring.
looking forward to being a part of the forum.