Airsoft sniper forum has some great guides on the specifics of building a DMR. The key is consistency, so gas isn't a great choice. HPA is a good pick if you really don't want to go aeg, but it's expensive. For platforms, some sites want you to have a real world full power cartridge firing weapon, some don't mind, some just want a fixed stock, check your local sites. Personally I'm using a nuprol ak21 with a UKSR stock, which has pretty solid externals so ripe for a DMR build, but it's based on an intermediate cartridge platform.
For power, it ranges drastically at different sites, check your local, it may not even be worth running dmr power. In which case may I suggest the precision assault rifle? Essentially the concept of a DMR at <1.14j, set to hop the heaviest bb you can as accurately as you can. I'll mention
@Impulse to preach about this further
I have been summoned!
So, I've done a lot of testing around this with my HPA m21 build and it really does come down to what you value more and what power limits you're working with. I will preface this by saying that I value effective range, so that's all the testing I work with. I don't care if you can spray your AEG at a 75m target and maybe hit it with 1 of 10 BBs, I measure if you the gun can consistently hit a man-sized target 9/10 times at a certain range. Some sites operate DMRs at 1.48J, which is utterly pointless in my opinion as you gain barely anything (I didn't notice any visible increase in effective range) but you trade off the ability to point-blank shoot, which can come up more often than you'd think. Some sites operate DMRs at 1.64J, which is a bit more arguable in its use since you do notice a slight difference. I noticed just about 5m more effective range (if that, honestly...) when running my m21 at 1.64J on .4s, however again you're trading off that MED for a, in my opinion, negligible increase in effective range. My local site runs DMRs at 1.64J with a 30m MED which I've looked at and decided I'm never running a DMR there because just about 5m more effective range vs not being able to shoot at anyone within 30m is a no-brainer for me. However, some sites allow DMRs up to 1.88J (which is what it was most places back when we measured in fps) with either a 20m or 30m MED. At this point I feel like you gain enough of a benefit to counteract the drawback, though mostly just in the marksman role, as I noticed I started to hit an effective range of about 10m more than my 1.14J setup while running 1.88J on .4s (I would probably use .43s or maybe experiment with .45s at this power, I just didn't have any). 1.88J with a 20m MED is where I'd run a DMR, otherwise I'm just going to run 1.14J or I'll use a BASR instead at 2.3J. I cannot stress enough how useful having no MED is; it won't come up all the time, but you'll remember every time you get hit out because you've had to swap to your pistol since the enemy are too close.
Running a 1.14J "DMR" is a great idea and I've had a lot of success with it, even with my spring TM VSR build which is also a 1.14J build (it's consistently around 1.1J). An effective range of 60m is what I've achieved running my m21 at 1.14J on .32s and it's more than enough; I've been out-ranging the braggarts who claim their AEG hits out to 70m and even contending with a lot of the BASRs people seem to run (a lot of people don't put enough time and effort into their builds...), so I'm happy with it. You can go heavier for a little more consistency, but I go .32s because after that is where ammo gets exponentially more expensive and the benefits I get from heavier BBs at 1.14J isn't worth the investment at the moment. Let me make a few career jumps then we'll talk again
For simplicity I was wondering about a TM M14, but have no idea what real life range that has out of the box.
Out of the box it... isn't that great. When you're trying to take long range shots, you really start to feel the 0.8J and the fact it can't hop much heavier than a .28 out of the box. I love my TM m14, but I've put a lot of money into it and wanted the TM externals for my HPA m21 build because it was going to be my magnum opus 1.14J build (and oh boy is it ever...). If you want something more affordable and you're not too bothered about a lack of trades / slightly worse quality externals, go with a Cyma m14. I have a Cyma m14 that I've set up as a Vietnam-era m21, though I will convert it to a DMR stock when I can afford one / one is in stock somewhere, and it's fantastic. It will likely come out of the box at around 1J if you order it in the UK (they're higher power out of the factory, but I believe most places reduce the power before selling them because otherwise they're a section 5 firearm out of the box!), but a quick hop rubber and barrel change will have it shooting incredibly well for the price point. My Cyma m14 build has cost me... about £130 in total because I got mine from TG before Brexit, but a Cyma m14 is £150 from Patrol Base, plus Maple Leaf macaron (£10), Omega nub (£5) and a ZCI stainless steel inner barrel (£25) will be a pretty powerful setup for under £200. It's what's in mine and while I haven't run it in a long time it was performing almost as well as my super-expensive TM m21 setup. Almost because it's not as quiet and not quite as consistent, but it's more than enough!
Upgrading the gearbox internals of an m14 isn't too difficult either, but it's a laborious process. Dismantling the m14 takes a lot of time and care because there are springy bits all over the gearbox that you have to remove to get inside since the fire-selector and trigger contacts are on the outside of the gearbox. It's easy once you know the gearbox, but the first time will take you hours...
I'm shit with electrics, better with gas guns. I'm comfortable with changing hop units / barrels etc.
You and me both; it's why I'm now transitioning away from AEGs (will use my NGRS 416d until I can get an MWS or more mags for my AKM). HPA for sneakybeaky, GBB for speedyboi clackclackclack. If you wanted to do a GBBR DMR build, I'd recommend the MWS platform on red gas. I haven't done my MWS build yet, but it's something I might toy with the idea if I can get the external parts to turn it into a mk12 SPR. Now, with gas guns you definitely lose consistency, however what you lose in consistency you gain in FUN. Seriously, I took my AKM out for its first game day over the weekend and my decision to start transitioning completely away from AEGs was just solidified in my mind. Every kill was more satisfying because 35rd magazines and cool-guy-oper8r-tac-reloads and firing it was an absolute blast with the recoil. You will get fantastic range on a GBBR if it's set up right and it's far easier to work on than any gearbox AEG, but it won't be the most "competitive" choice. However, that can be a wonderful catalyst for improving your drills and general gameplay performance as you're essentially playing with a handicap that you'll have to make up the gap with your own skills.
Anyway, that's enough from me. Thank you for coming to my TED talk.
