Ok, so it's time for a build. There are two fields that I play at, my outdoor field has a 400fps limit and my indoor field has a 350 fps limit. I put a Promy MS100 in my backup M4 (mostly stock G&G Full Metal) about a year ago and it shoots above 350, I don't remember the exact FPS but I can't use it at my indoor field. As we come into winter I'm going to want to start playing the indoor field, so a CQB build it is. I have future plans of a DMR for my current backup so I bought an almost brand new Full Metal G&G GC-15 M4A1 off ebay as my base platform the the CQB build. The hand guards are coming off and I'm going to install a free float RIS on it, i'm going for the SD look. I'm thinking about the Madbull Gemtech Licensed T2 RAS kit paired with a ZCI 300mm 6.02. Or I will just try to piece together the correct RIS, outer, and suppressor for the correct look. I'm going for 35-40 rps and 350 fps Undecided on bearings or bushings also undecided on what motor and gear ratio to go with. I currently using 7.4 volt 25c constant/50c burst Turnigy lipo's, I use 2 of them at a time with a parallel connector so I double the availability. I'm hoping to be able to use the same Lipo's in this build. I'm also not sure on the spring, from what I read the Promy MS100 should get me where I want to be FPS wise but I have it (granted brand new still with very little use) in my backup M4 and it shoots too hot for indoor play. My backup is mostly stock but I did shim it and get the compression as perfect as I could. Below is a cursory list of part's I have put together. I would love to hear the opinions of the more experienced guys out there. Gate Titan VFC Selector Plate Lonex Hopup G&G Green Bucking Maple Leaf Nub SHS HS Motor or HT SHS 14-Tooth High Speed Piston Prometheus NEO POM Piston Head Lonex Air Nozzel SHS 12:1 Gears Lonex Anti-Reversal Latch Lonex Ball Bearing Spring Guide Sorbo Pad,Scatterplot,1/8”/Hardness:70 Tappet Plate--Guarder if I can find one in stock someplace 6.02 ZCI, 300mm Inner Barrel SHS 8mm Steel Bearings or SHS 8mm Steel Bushings Spring-Prometheus MS100S----????????