As one who has traveled with pb gear, and knows the regulations inside and out, here is the deal. You CANNOT carry any sort of pressurized containers in checked or carry on luggage. That said, if you need to carry you HPA tank, the regulator must be removed so the TSA agents can see inside of it, and also as proof of no pressurization. Paintball markers, whether military look alike or not CANNOT be in carry ons. DO NOT EVEN TRY! You would be charged with trying carry a weapon on board an aircraft. Even if it it has no hopper or air tank, it doesn't matter. Its still a airgun, or what the official term is a "facsimile weapon" (i think its what they call them)
When checking your luggage notify the agents of the materials, let them look at at (especially the airtank). Make it clear they are not real weapons and are harmless without air and paintballs. of course some TSA agents are idiots, so go to the website and print off a copy of the regulations covering proper carriage of airtanks, and paintball/air gun/ real steel weapons so that they cannot argue with you when you properly pack and check your luggage according to their rules. Be nice to them if there is an issue, it will help you alot. I personally print off a list of pb gear that is in my luggage and place it on the top of the stuff inside the bag. That way, the agents who lok in your bag in luggage screening have a better idea of what they are looking at in case they dont know what paintball is. Give a light description of what it is, like for the marker id say- "paintball gun/marker, used for playing the SPORT of paintball, only works when high pressure gas tank is used along with it"
for the airtank- "air tank disassembled, unpressurized container"
It wouldnt hurt if you put a note about the tournament you are travelling too, and so they know you NEED THIS STUFF" just in case they think its a hazard, they might be more inclined to do quick research of the sport or tournament before confiscating items they feel could be contraband. Remember, TSA agents are humans too (sometimes) haha, and they make mistakes. So help them understand its not a weapon or a safety issue.
Powered flight and Paintball, what more do you need?
Rear wheels first please, ever heard of flare?