You should always consider all the factors involved in purchasing and using a GBBR (and any other gun for that matter). But with GBBR’s, it is very very expensive, time consuming, and just the exact opposite of aegs. If you want to discuss the pros and cons further, don’t hesitate to comment down below! With gbbrs, its either buy expensive, or dont buy at all. If you buy cheap, it will break within your first week of using it. Using a gbbr is even more complicated than using an actual firearm. Unless you have money to burn, I would advise against purchasing one. If you do indeed have money to burn, message me and ill give you pointers. The gbbr world is... long, hard, and painful (thats what she said). Its also very very expensive. Nothing will beat RA tech parts. The problem is, you have to upgrade your WHOLE gearbox with RA Tech. This is because RA Techs parts are made of steel, which is harder than aluminum. Once the gun starts to fire, the steel parts will rub against the aluminum parts. Since the steel is harder than the aluminum, this WILL destroy all of your parts in your gun, I guarantee it. After a complete overhaul of most of the internals, I would upgrade the barrel and bucking. Im not too keen on what you should do in that department, hopefully someone here knows more than me (very very likely). The bolt by the way, is what I mean by most of the internals, the bolt is the part that moves, and anything touching it that isn’t steel will be destroyed. Another crucial part of the internals is the nozzle. I don't recommend the aluminum nozzle by ra tech, there just seems to be too many problems with it. I don’t know what nozzle is best (again people on here know so much more than me). Also, here is a quote from a guy on reddit, he basically sums everything up: “If upgrading down the line to anything steel. It's always a good idea to match the type of material for parts that have direct contact. For example, steel trigger box will need a steel bolt carrier for minimised wear on the bolt carrier. But in turn, the steel bolt carrier will now need a steel bolt catch to also minimize wear on the bolt catch.” The rub is that with a steel bolt carrier in any gbbr, your gas system now needs to cycle a heavier mass than the stock alloy bolt carrier. To maintain efficiency and cyclic rate, you could try upgrading to high flow valves in your magazines to compensate for the extra oomph needed to cycle steel. I would recommend buying the upgrades over time to have on hand while you wait for the stock parts to live out their use instead of gutting them right away. Also, plastic nozzles are just a better option in m4 style gbbr because of the "feed ramps" having those locking arm cutouts. Plastic hitting metal when misaligned is more forgiving than aluminum on steel or something like that sending metal shavings all over the place over time. Magazine Information: You probably don't want the co2 mags (if that is indeed what you're looking at). I think you might be able to use G&P, and EB-Tech mags.. MAYBE. However... Most people are trying to use the GHK mags in their other platforms, because they're considered to be the best mag currently on the market in terms of performance/weight/maintenance/etc. GHK mags (the green gas ones) can also be modified to accept liquid Co2 from a paintball Co2 tank. This is called the DevilHunter mod, and will increase your recoil and let you play in colder temperatures. You can also get used mags for cheaper. Beware, however, that there are two types of mags. The old mags are much heavier than the new ones. G5 mags are the old polymer style ones, while GMAG's are the new lightweight polymer style ones. The same applies for the STANAGS, but they don't have different markings to differentiate them that I know of. You can use the Ghk G5 mags and I honestly wouldn’t use any other brand considering how awesome ghk mags are. I’ve never had any issues at all with ghk mags in terms of cool down, leaking, and/or durability. The only issue is that their metal AK mag lips are a little too tight. The price is definitely worth it imo Gas Info: I would go with propane (green gas mag) simply for the convenience factor. Its so much easier to carry one propane tank than a bunch of c02 cartridges (gbbrs eat co2 for breakfast and have room for more). Propane (with lube of course) is a cheap and reliable way to run your gbbr. Thats just the basics of running a gbbr though, there is a whole world of knowledge to know about them. Let me know if you have any questions regarding gbbrs and how they are powered. If you also have any questions regarding propane, that would be great too. I’m happy to help, so feel free to message me anytime. Hope this help! Id appreciate the upvote! I’ll update if I think of any new info, hope this helps! One more piece of advice: GHK is the literal Ferrari of gbbrs. The parts in it stock are miles better than WE, you just gotta maintain. maintain. maintain. In the end, you’re gonna spend just as much if not more on your WE gun than on a GHK gun stock. If you have the opportunity to go GHK, do it. You’ll be miles happier. Brands such as Kwa, vfc, matrix (gross), and others are highly problematic, and honestly, should be stayed away from. All this information is not just my own, but if info I have gathered up over a while of reading. I’ve just put it here in a guide, so you may feed on the knowledge I’ve collected. Be sure to message me if you have any questions, comments, or concerns! Good luck on your gbbr journey!