i have build it only with one bolt not like the original one with 2 bolts.the mag has a size of 8 bricks.it has custom version of the open bolt mechanism.
My last mech hasn't gear to accelirate round and rubber band live more(one-about 70 shots). Yes, closed mechanism works more stable.Also good design in m14 =)
I think the Open bolt mechanism much better it shoots every time.and by the closed bolt the rubberbands breaks too often.i dont care if your Gun has a moore effective range. In my opinion the Open bolt is much better.
To bad, my l85a2 has the effective range for about 7 meters, then it fall down for 2 meters. I think closed mechanism(like in streat's l96a1 much better)