I have been building a custom MK18 for the past couple months and I have finally finished the internals. However, when I went to assemble the receiver, I encountered a problem. The receiver would not fully close (when sliding the upper on top of the lower) I realized that my Hop Up was not allowing the gun to close.... Any suggestions or fixes?
I am using a Madbull DD 10.5" barrel with G&P stock hop up with Madbull python tight bore.