[T@NK]

According to my experience, all the mods to the gun serves one purpose: make the gun function smooth in the long run, reduce any protential possibility of damage or malfunction.
thus I would suggest upgrade some possible parts:

1, real steel upper reciever

I 've read through some Tiwanese forums and some players had some broken upper situations caused by the air bubble in the early version stock metal upper recievers, a real steel will not have this kinda issue.

2, a steel trigger group

Either CWI or RA-Tech will do the job, they are much durable than the stock one, some ppl complain about the malfunction of the RA-Tech set, I guess that might just depends on person, mine RA-Tech trigger sets never have any issues through the passing year. get what is available for you.

what I won't suggest you to get:

1, RA-Tech steel BCG + Alluminum bolt

the RA-Tech steel BCG do more damage to the gun than bring in the good, unless the RA-tech make a steel CNCed hop up chamber, I won't use it anymore otherwise. the stock hop up chamber was shape-shifted due to the strong impact of the steel BCG in my gun, I was doing some major maintainance on my weapon last week and found out I couldn't the the hop up chamber out of the upper because of that. while my buddy's WE m4 has little wear on his hop up chamber with stock BCG in use.

Alluminum bolt + steel BCG will smash and crack the jamming BB inside the hop up chamber if there is any jamming happens and do even more damage to the hop up chamber. if you have a jammed gun in the gun fight with the metal bolt and steel BCG in the gun, you are gonna have to field strip the gun and use some tool to remove the cracked BB from the chamber, which is deadly. the stock plastic bolt works just fine, it will crack itself when jamming occurs, but after that you don't have to worry about it anymore, I found a cracked bolt works even better in my case, coz next time when the jamming happens, the jammed BB will just bounce to the crack area so it won't damadge other parts of the bolt. the stock plastic bolt won't smash/crack the BB in the chamber, all you need to do is remove the mag, rack the handle and let the jammed BB roll out the the chamber, insert a new mag and you are good to go.

To gain some not so noticable recoil by increasing the risk of breaking your gun or get shot, It's really not worthy in my book.

2, TB inner barrel
stock inner barrel works just fine, for the open bolt system. I was cought with a jammed gun early this year in OP Shallow lake, turns out there was some dirts got into the barrel through the ejection port during the shooting, dirt + 6.03 barrel = jamming, then what about 6.01? you get a higher chance to jam with a TB Barrel anytime. note that your rifle doesn't shoot as far as a real steel m4 nor you are a sniper that you are gonna pick you target off miles away, accuracy doesn't really matter that much in airsoft as long as your BB doesn't fly way off the grid.

Know your gun is a toy, and know what a toy can do, know it's limit will help you run well.

My 2 cents

Tank