I am new to building guns so if some things don't add up or there are better parts than the ones listed let me know. So as the title says above, I am building/upgrading a M4 with a goal to shoot far and accurately with a budget for around $1000-$1500 if need be. I have come up with a loose parts list for it so far: Internals -Polar star fusion engine v2gen3 -455x6.23mm widebore Orga inner barrel -a few polar star nozzles to tinker with the fps to get it under a 410 limit. (I will also need to experiment with bb weights .25 to .36) -As for a hop up unit I have little experience with but I was told they are very important too shoot far and to go for a Prowin because they are supposedly pretty robust. Need some help with this one. -Nub? I was told something about r-hop/er-hop/ir-hop/flat-hop and it sounded too good to be true but if it is that good I could use some info. -And another hop up related question I am too inexperienced in is bucking. Need info on that too. Externals -outer barrel http://www.evike.com/products/52602/ may need to find a better one. -I'm looking at some externals/bodies now if you guys have any suggestions for some nice ones. I'm thinking about just gutting a M4 and dropping everything into it. -As for stocks, I will probably just use the one an M4 comes with or if one of you has a good recommendation I'll be sure to check it out. -Same goes for a rail system or any other externals. -If you know of a nice medium range sight/scope let me know. If I left anything out also let me know.