Hello im back at it again. I gave thought to this idea a long time ago but now with more moding experience im ready to tackle it. I know theres ones i can buy but i want to build one from raw materials. I plan on using rectangular steel tube for lower FCG and use ar 15 fcg. Also use a uzi mag well or pistol grip. My upper will be rectangular or tube steel depending on my bolt. Thats my hang up is i need ideas on a closed bolt either square or round thats not $150 or higher. Anyone have any ideas?