Chronicles of a bad idea: Building a Mk12 Mod 1 Recoil

A little background before I delve into the guts of what has turned into the single biggest project I have taken on: I am not a smart man and I have always had a soft spot for the Mk12. The Mk12, both Mod 0 and Mod 1, has been a dream rifle from my early days in airsoft till now but through one thing or another (mainly buying other shines) I have never had a chance to own an AEG or other version. the VFC GBBR version does please me but I’m still on the fence about gas rifles with our climate in the UK.


This project had a strange beginning: Dan Shears (Mong the Merciless of Red Troop fame) built himself a copy of the rifle used by Axelson in the film “Lone Survivor”. It was that good to have been featured in US airsofts top 5 Marui builds, coming in second.


Now I will say that his was an impressive build and half of the reason I started my own. His build (like mine) was based around the use of the D boy’s Mk12 front set which comes with the complete Rail, Barrel, Gas block and tube. The barrel nut goes onto the recoil upper receiver with no need to recut the thread but the barrel needs some modification to fit, the barrel however is far more complex.


From stage left we have Airsoft International magazine who did a complete build guide of a mk12 mod 1 (solid stock version) using the afore mentioned D boys kit. It gave a step by step guide showing how to modify the barrel to fit. This involved careful grinding, filing and sanding of the joining portion of the barrel to sit in the recess on the upper receiver (to this day im still not convinced on trying to do it yourself). A lot can go wrong here as once you take off too much material you can’t put it back and can lead to a barrel that does not sit straight no matter how many barrel shims you use to hold it in place.


The other half reason of me taking on this project was the stock. Dan did the sliding stock version (again, Axelson impression) but I NEEDED a solid stock. Again AI magazine stepped in and showed how, using the standard recoil buffer tube, to cut, dremel, file and sand down an AEG solid stock to slide over the existing buffer tube and attach it so as to give you a solid stock option. From my point of view (and at the time of seeing the original article) this was pretty much the only option for it and looked very tidy.


So with the how to do it in place, around 18 months ago I started looking for a Marui recoil to start this project. As luck would have it I found the perfect starting rifle: A partially complete mk18 build with a solid stock. In hindsight it probably wasn’t the best of starting points (I shall explain why in a bit) but it had some interesting features that was great for the price I paid (or so I thought) at the time: A custom buffer tube made by LCS Engineering with solid stock to fit Marui gearbox with the bushing holes drilled out from 5.9mm to 8mm and a BTC Spectre All of that in a built, working (or so I was told) rifle with 5 mags for £420. Bargain I thought! So after messaging the seller and a few questions later money exchanged hands and I had a good start to the mk12.


Oh how wrong I was.

The rifle upon arrival had a broken charging handle. No worries I thought as it was probably broken in transit which is not uncommon. The problems didn’t end there though. It refused to feed off any of the mags that came with it, the fps when it did feed a round was well below what was advertised, the thread on the end of the barrel was completely stripped and the gearbox sounded a little grindy. A few more messages to the original seller and as I started stripping down the rifle confusion started setting in as small parts started looking a little out of place. Then it dawned on me as I looked at a lower receiver with stripped threads and No Marui trademarks that all wasn’t as it appeared.


My Google-Fu is strong and a little investigative research later led me to conclude that the base rifle was an Army Armament clone with a genuine Marui gearbox at its core. Now I wouldn’t have been so bothered about this but the upper receiver thread had been recut for the mk18 rail that was fitted and as such no other rail would fit, so my idea of using the Dboys rail appeared pretty well out of the question. Also 2 of the bearings fitted in the gearbox had imploded. Well shit. Long story short and a few more messages back to the original seller and an agreement was reached whereby a refund to cover the cost of replacement parts was met.

Now the real fun could begin. Eagle 6 has been my go to for recoil parts ever since I first picked up a recoil Scar-H (still own it, still love it) and soon my shopping cart was full of original Marui parts to get the rifle back into some semblance of working order. At the same time an order was placed with Mlemart for the D boys Mk12 front set and a Dytac 18″ Spr profile barrel specific for Marui recoils.


A quick message from Mlemart however threw a new problem into the works which would result in a 4 month, many phone call and email search. Dytac in their infinite wisdom sold the spr barrel with the correct 2 piece flash hider, gas block and tube, Or used too. They discontinued the flash hider and as a result no longer came with the barrels. Here is where the problem lies: The Dytac barrel is correct 18″ length with the 2 piece flash hider. The D boys barrel is 16″ with a 2 inch extension that also has both pieces of the flash hider welded to it. I could use the extension as a gap filler until I find the correct flash hider but it looked so, so wrong.


So now faced with the task of tracking down a discontinued part (Dytac and G&P ones have apparently been discontinued for a while) I set about trying to figure what I wanted this rifle to be at the end. I have a lot of respect for the guys and girls that build rifles to reflect real world units or doing impressionist loadouts of fighting forces around the world but I am not one of these people. I’m the guy that rocks up to a skirmish wearing jeans and an Hawaiian shirt (or Kryptek depending on my mood) so an accurate replica of a military unit rifle was out of the question. I decided to do a mix of military and civilian aspects of the mk12. I had a few months previously found a picture of a  mk12 inspired civi rifle. This inspired me, and decided that I wanted my rifle to look similar



Externally with not attachments it would look identical to the military version whilst I would borrow ideas from the civilian shooting world with regards to optics, bi-pod and grips. I HATE the Harris bi-pod: Its heavy, boring and everyone has one. Luckily another member of Red Troop (who loves me far too much) had a spare Atlas Style bi-pod doing nothing…… so I stole it. The optic was a no brainer. Airsoft is not real steel so we don’t need the equivalent of the Hubble Space Telescope mounted to the top of it but I still wanted an optic that looked correct on the top of the rifle. The Visionking Short dot was the obvious choice with its superb clarity and eye relief and coupled with a clone Larue SPR 1.5 mount looks spot on to the reference photo of a civi spec mk12. I had also seen Mr Monkey have the same sight set up on his 416, which I liked very much. Again looking online I found a number of photos that had the mk12 with a Scmitt and Bender 1-8×24 of which the vision king is aesthetically similar.


I present Monkeys rifle to show off the Visionking short dot. I make no apologies for the pink mag.

Irons sights came courtesy of my Ex-Wife who didn’t know what to get me for my birthday so I ordered a set of clone Troy Style folding battle sights and whilst not correct for the rifle, they looked plausible,  and lets face it im not going to be using them that often.


As for the Grip (both shooting hand and front vertical) I went for a Magpul Pts MIAD grip (for the ability to swap out the back strap for my abnormal hands) and the classic KAC Style vert grip.


So Moving to the internals, I wanted to achieve 2 things: An accurate sub 350fps rifle with no MED at regular games. An accurate plus 400fps DMR at Milsim/filmsim/apocalypse style games. The LCS Engineering buffer tube gives me the unique ability to hot swap springs in 60 seconds depending on the sites fps rules and what I feel like doing on the day. Its a seriously well made and engineered tube and well worth the price.


Having a Btc Spectre already fitted save me a lot of hassle and wallet heartache trying to find one ($350 for a spectre?!?!?!) and is already locked off to single shot all round as id damn well should be for a DMR!!! I have no intent on using burst or full auto for the games I play, I had a SCAR already for when I wanted to go up close and nasty.


The rest of the original  gearbox was a mixed bag of good and WTF. I have no idea who makes the gears but they are not original Marui and probably will be replaced with Lonex gears for peace of mind at some stage (cause im not paying £110 for prommy ones). The Spring guide, cylinder head, piston and piston head are all Magicbox whilst the cylinder is a Lonex Full type and all came prefitted to the box. With the length of the barrel and some very quick arithmetic full cylinder appeared to be the right way to go.

Whilst I have no reason to doubt the QC and strength of MB parts I will be going full Prometheus on the internals, aside from the gears as already stated and the cylinder which will be Lonex. Im also considering a Lonex cylinder head modified by Airlabs for Sorbo to correct the AOE and provide a little more air seal.

The motor is an Element high torque and has been pretty damn good so far although I have been tempted to go to a Tienly motor for the added torque. Hop has remained as the original Marui hop unit (thank you Mr Marui Man and your hop units made from dark matter)

For barrel, I picked Prometheus Returner barrel (455mm) for its slightly wider hop window and 6.05 bore. Ive had a little more success with wide bore over tight bore, Id seen both Monkey and Mr Shears have some pretty good success with using these barrels. I also have the tendency to crawl through mud and other random materials trying to sneak up on people. Monkey in particular (who does a similar array of ridiculous things) had found the returners to be more forgiving of dirt, grime and the blood of thine enemies.


I coupled the barrel with a Prometheus purple hop rubber and flat hop bucking. While the Marui stock rubber is a thing of beauty (mine lives in a shrine and is worshipped regularly) the prommy seemed a little better at lifting heavier bb’s at higher velocity. The last time I took this out for range testing it did well, quite happily lobbing 0.28 and 0.3 through a window at about 70m. Much to the annoyance of those with shorter ranged rifles.


So here I am, 18 months on from the beginning, and although an Rhopped barrel is not out of the question for the future. It has to be said that bar a few tweaks at this point the rifle is complete. I want to tweak the internals at some point as I am suspicious there is an air seal issue in their some where, but I am in no rush. for now, I am enjoying what the rifle is and using it in game as much as I can.


It has been skirmished both by myself and Monkey and in his own words “it was glorious”. There are more accurate and longer ranged guns out their and I look forward to seeing one, but have not yet found one. Having the flexibility of being a standard AEG fps and then 60 seconds later being a site limit DMR is fantastic and makes this rifle a flexible beast.




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