nathan13n

Building the Ultimate Lightweight HPA LMG: My S&T M249 MK2 SAW Project Going through my airsoft collection, I realized I was missing one key piece — an LMG. Naturally, I thought: why not? I didn’t expect it to become one of the most frustrating builds of my airsoft life. From the start, I knew I was going to HPA it, especially since I had a Backdraft Phoenix engine lying around — a solid engine, though a bit inconsistent in DMR roles. Why I Picked the S&T M249 MK2 SAW Let’s be real — the S&T M249 is just a rebranded A&K Featherweight (also sold under Cybergun), but with a few advantages: V2 gearbox (sounds great at first… more on that later) Lightweight — only 4kg, compared to 5.5–6kg for most other M249s Cheap — cost me just £200 At first, the V2 gearbox and light weight seemed like a win. But that big proprietary nozzle and body flex quickly turned into a massive headache. Out-of-the-Box Performance Running a 7.4V battery, it gave me: 12 RPS 1.1J 30m accuracy with a torso-sized spread Not bad for £200. Decent compression, a metal rack piston, basic MOSFET locked to full auto. It worked — but it wasn’t good. Goals for the Build Fix the weak plastic stock Tighten up the shot spread Increase rate of fire Get consistent mag feeding The Build Process Body Flex & Rail Replacement Because the gun is so light, body flex was a huge issue — even minor misalignment can cause major problems with HPA. I replaced the plastic top and bottom rails with metal ones and added bracing plates. This significantly stiffened the gun and improved alignment. Engine & Electronics Installed the Backdraft Phoenix HPA engine and wired it to a Gate Aster II for better control. Problems started immediately: Sporadic shots Inconsistent feeding Laser shot followed by a 2-meter fart Hop-Up & Feed Ramp Hell The stock hop-up is garbage — cheap, flimsy plastic with lots of flex. Swapped to: Bullgear Featherweight M249 Hop-Up — improved consistency, but feeding issues remained Tried: Drilling stock feed ramp — BBs jammed Anttech feed ramp — flimsy 3-part design, reintroduced flex and made things worse Final Solution: Found a 3D model of the original feed ramp by Gazadonf77 Printed in PA12 nylon (MJF) via 3D People Game changer — fixed all feeding issues Bucking & Barrel Testing Bucking Results: Prometheus Purple: Good but had flyers every 5 shots Quantum: Best range (50–60m), but overhopped everything and grouping was meh Maple Leaf 60°: Winner — torso-size grouping at 50–60m with 0.30g BBs, great price-to-performance Tip: With Bullgear hop-up, use high elasticity buckings. Stiffer ones perform worse. Barrel Results: XT 6.00mm: Tight bore, low PSI, bad consistency ZCI 6.02mm: Better, but still not quite there Stalker Morpheus 6.03mm: Extended crown = more range (70m), but groupings were wild PDI 6.05mm: Winner — 55–65m range, best consistency, 2–3 inch spread. Uses more air but totally worth it. Magazines: A Comedy of Errors The stock S&T mag (9V battery) fed only 12 RPS — upgraded to 7.4V LiPo, gained speed, then shredded the gears (poor plastic internals). Tried: Lonex 200rd & EPM1: Fed great, but too low capacity for an LMG Classic Army M249 mag: Worst of all — inconsistent, weak, loud motor Novritsch M249 mag: Winner — actually a rebranded A&K 2000rd box mag, fed up to 30 RPS on both 7.4V and 9V. Responsive mic, auto shutoff, and only £75. Stock Upgrade The original SAW stock is huge and ideal for batteries, but looks awkward and feels cheap. Didn’t want to pay £50 for a CNC adapter, so: Found an STL file by CitrusPers - Stock adapter Got it printed by 3D People Now using M4 buffer tube + compact stock = lighter and more ergonomic Final Build & Cost Breakdown Part Price S&T M249 MK2 £200 PDI 6.05mm Barrel £60 Backdraft Phoenix HPA Engine £250 (already owned) Gate Aster 2 £65 (already owned) A&K 2000rd Box Mag £75 Bullgear Hop-Up Unit £60 Custom Feed Ramp & Stock Adapter (PA12) £50 Total: ~£760 Final Verdict What I have now is a lightweight LMG, feeding 0.30g–0.32g BBs reliably, with: 55–65m effective range Consistent grouping (~2–3 inch spread) 30 RPS at 1.1J 3,500–4,000 rounds per 48ci tank @ 70 PSI Great for suppressive fire, fun skirmishing, and surprising people who think it can’t reach them. Would I do it again? Probably not. Am I happy with it? Hell yes. Little video of the bad boy shooting

Funnily enough this popped up in the whatsapp chat recently. Airtac doesnt listed it but they recommend running the N4 between 100 - 150psi ( i wish they would put it on the website it would save so many problems). As Gaintkiwi said run it at 100pis and use the NPAS. The best ones to recommend are Feda concept or Jager precision. On the stock nozzle some people complain the npas doesnt hit well but they fit great into the Guns modify nozzle.