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aac

aac's MK12MOD1 build

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Intro  

 

Started a new project build, with my newest asset the CM.072  check here my review.

 

The CM.072 actually is an hybride beween the SR-25 and SR-15, i wanna make an MK12Mod1 with it , that's the model we al have seen in Lone Survivor, below some of my reference pictures.

 1488552271326.jpg

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What does that actualy mean ?

 

To made by myself:

 

  •  The CM.072 barrel (in SR-25 style) to be replaced by a custom made steel Mk12 18" barrel.
  •  Making of an Allen Engineering SPR muzzle break and collar
  •  Making of an Mk12 low profile gas block
  •  The CM.072 in SR-25 style has a cutout for the frontsight, and need to be modified.
  •  The ARMS#22 high rings doesn't exist in replica version, so that wil be a milling job !
  •  Mk18 front sight, i have a nice one, but needs to be modded a bit
  •  Problably i wil make an Allen engineering Mk12 suppressor
  •  Weathering paintjob

 

To be replaced:

 

  • The fixed stock of the CM.072 wil be replaced by an M4 stocktube, and Crane stock
  • The CM.072 fire selector, and magcatch wil be replaced by standard types.
  • The Magpul pistol grip wil be replaced by a Colt A2 model

 

To purchase / mount:

 

  • Harris style swivel bipod  (stil searching BTW so if someone still as laying one around)  :)  
  • Leupold Mk4/M3 scope
  • LA-5 peq box
  • KAC frontgrip
  • KAC railpannels
  • The KAC 600M of the CM is awesome and wil be unchanged.

Here once again the CM.072 for comparison.

 

image.png.d1a2d89b57ef78f3bf1e152781fe1f

 

 

 

 

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Chapter 1: The barrel group.

 

Since i made my intro into the 21e century, and -even i- am "armed" with a smarphone today, in can easier make my progress pics.

 

The barrelgroup is relatively simple, witch makes the manufacturing progress going pretty fast, the barrel drawing is ready to find with Google, and the other parts could be pretty easy R&D'ed with the help of photo's, ruler, and calculator.

 

Muzzle break

 

Finaly started with the SPR muzzle break, this is indeed a muzzle break, instead of a flash hider, he's besides developed in such a way the gasses are forced back into the suppressor.

 

Bellow the muzzle break in various steps, de serrated ring actualy is the thread protector, to be used when the suppressor is not mounted.

 

uLZPNAv.jpg

 

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Mk12 Mod1 18" barrel 

 

This is original a "Douglas Barrels" match grade barrel, a simple straight design, here's mine on the lath, the base material is mild shaft steel

 

ATOGArd.jpg

 

 Making of the AEG receiver adapter detail, milling of hop up guides, and cutouts 

 

11oUCab.jpg

 

Making the innerbarrel fitting

 

This 18" barrel is pretty long, and in fact i dont have the perfect tools, to make such long drills, perfect straight and precise, thats why i decided to dril the barrel with Ø 10 (way bigger than the innerbarrel Ø 8.5)

Then i made some copper spacers , loctite-glued them on the innerbarrel, and sanded them until the barrel fitted smoothly into the outerbarrel.

 

6iKD1ik.jpg

mOMzuIU.jpg

 

Finaly the innerbarrel appeared about 35 mm too long -for estetical reasons- actualy the barrel passes true the muzzlebreak, and is visible true the "windows" of the AO SPR muzzlebreak

 

HsDGMk4.jpg

 

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Mk12 gasblock

 

Original drawings are ready to find on the web, besides you guys saw me making this parts already multiple times  :)

 

In fact this gasblock is originaly developed for the Mk12 , but also used on the Mk18mod1

 

Bellow once again the different manufacturing steps

 

4Ok2pIH.jpg

 

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In composition

 

Meanwhile al the parts are ready to be adjusted to each other, the collar is also visible right now (the progress was going so fast i forgot to take photo's)   

The collar serves as centering for the AE suppressor .

 

G4PghTH.jpg

 

Finishing phase

 

Al the parts slightly sandblasted, to provide beter adhesion of the Fosco paint , the spacer ring, and threads are originaly  bare stainless steel, to simulate heat tarnish i threated the parts with the acetylene torch.

 

DMSp5gx.jpg

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Assembly phase

 

Al the parts painted ready for assembly

 

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Barrel and gasblock mounted

 

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Collar and muzzle break installed

 

pynuT9c.jpg

 

Overal view

 

z5w5gMu.jpg

 

Then the whole assembly slightly weathered with Scotch Brite

 

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ObUF60K.jpg

 

The rail installed

 

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Here we see clearly the cutout at the front of the rail, for the SR-25 sight, witch need to be modified.

 

g0eeMxy.jpg

 

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Rail modification

 

To make the SR-25 rail looking as a KAC M4 free float rail (Mk12mod1) i milled an insert out of aluminium, the insert is loctite glued, and tight fitted into the gastube channel of the rail.

 

mpb7GTT.jpg

 

De picatinny extension part itself

 

5G4TmkF.jpg

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The front tooth of the front need to be removed because he is chamfered.

 

iUBfzSE.jpg

 

And the insert installed

 6eZBcI1.jpg

fytYgwR.jpg

 

And painted

 

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Before & after

 

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....................................................................................................................................................................................................................................

 

So far so good, more soon so stay tuned and hit the follow button  :busted_blue: 

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Chapter 3: The A.R.M.S. # High Rings

 

image.png.221d4942a98231df1d7c4827751795

 

These are the most chalenging parts of this project !

Of al the scope mounts in the world, are the ARMS problably about the most complex of al, and of coarse the Crane Division selected them for the Mk12 , lucky for me there are pretty much photo's ready to find on the web.  :)

 

The "base" is made out of aluminium, and clamped to the picatinny rail with a throwlever system, the scope ring's itself are made out of steel, and attached to the mounts with a dovetail.

 

Completely coincidental i started chatting with an American who was building an Mk12 to, it appeared it was a RS sport shooter to, and even in possession of the real A.R.M.S mounts, the good man was besides so helpful, that he offered me to make some measurements and give me feedback and photo's on request ! 

 

Sometimes you need to have some luck to !  :)

 

The mounts:

 

Below the first progress of the aluminium basemounts, because both are mirrored, i let them attached ,  this to avoid mistakes, and 

it saved me a lot of machine adjusting.

 

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And then it was time to separate the Siamese twin  :D

 

image.png.11cad4ab038a059deb15246ae9ab15

 

 

The Scope Rings

 

Here i want besides using the ARMS TRC (Tactical Ring Cap) this is a scope ring with a small piece of rail, it makes you able to mount a Mini red dot on top the scope, it looks besides very tacticool IMO  :D

 

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The first milling work on the TRC cap

 

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So far so good, more soon so stay tuned , and hit the "follow" button ! default_wink.png

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My today milling progress on the scope rings

 

dETGjjN.jpg

iFCvKsT.jpg

fPXVAVH.jpg

 

The dovetails are welded on the scope rings and milled to size

 

Q3oQBP3.jpg

 

And on the lath, ready for machining the 30 mm scope diameter

 

xRqMZxh.jpg

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yes! Imagine my surprise when I pull up Arnies and this is the first thread I see. I still expect you send me progress updates on Facebook too, though!  :D  

 

this is going to be an awesome build when it's finished!

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Some new progress, bankworking & adjusting of the throwlevers and QD system.

 

wu0xAx3.jpg

TqOQ040.jpg

 

And here a preview with my new Leupold M1 scope

In fact its a bad buy of me, should be an M3,  but i didn't notice the longer turrets made it an M1 at the moment of the purchase

 

aAbAOZO.jpg

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Here my latest progress, made the "recoilbar" ,and pressureplates

 

image.thumb.png.f21791fe585913ca7e488375

IsTzgQv.jpg

 

Al the parts painted and ready for assembly

 

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Fully assembled, and slightly weathered as usual 

 

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xaPFIuJ.jpg

 

Also the first progress on the ARMS#32 bipod mount

 

O63mEH8.jpg

2UrP4LF.jpg

CNF8OW2.jpg

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A next chapter in my MK12mod1 project, The Allen Engineering AEM5 suppressor

 

This was a relative easy item to make, lathed out of plain soft steel, and brought to the right weight (about 600 gram's) this suppressor go's completely over the muzzle break, is threated, and centers onto the collar, a simple, but effective design!

 

Bellow in a few steps the progress

 

The base material; plain mild steel.

5J6rfBs.jpg

 

Adding the markings

 

TJC054q.jpg

 

A view on the adapter section, note the chamfer witch fit onto the collar and center the suppressor into the barrel's axis

 

2uA3ZQ1.jpg

 

Overal external view, note the shallow knurlings , just as the original AEM5

 

pF6IR8R.jpg

 

Then made my actual first attempt on working internals; after following for a long time topics -here on Arnies- i choose the "cutoff disc & expansion chamber- design" i saw also somewhere (don't recall where anymore)  the concept of placing thee disc's on different distances, should "break" the soundwave, or something like that ?

I made it al in an open cell foam, and the replica has definitly a duller sound with it !

 

I made this paint-draft to make it al clear  :busted_blue: 

D55VL8c.png

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Then it was time to press in the endcap, and made the flush finish and charateristic AEM5 detailing 

 

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Finaly painted the suppressor in Fosco Grau Blau, and did some slight Scotch Brite weathering, (more photo's soon)

 

u47VGQY.jpg

 

So far so good, more soon so stay tuned , and hit the "follow" button ! default_wink.png 

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This whole build is insane. The stuff of legends.

 

Bravo.

 

 

Absolute fantastic machinework

Thx for appreciating my work guys  

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Chapter 5 : The lower receiver assembly / modification's

 

As mentioned before,  here i needed to swap some parts to become a "proper" M4 lower receiver

  • Fixed stock for an M4 stocktube
  • Ambi magcatch for a classic
  • Battle arms fire selector for a classic
  • Troy trigger guard for a classic
  • Magpul MOE for a Colt A2

I found these parts in an FB airsoft sales group, bought the parts for less than the shipping cost's, and received the ((plastic) G&G lower, and CQC slingplate with it for free, from the kind man :) 

 

image.thumb.png.7a5143fe202e38eb7efdda1f

 

The Gearbox

 

Initialy i wasn't planning anything with it, since i only shoot sporadic with my replica's, but after al the work on the externals, i found i needed to make a minimal effort to upgrade the gearbox, i would'n dare it to call it a real gearbox upgrade btw, more some optimalizing of the existing setup or something.

 

And indeed, there apeared to be no noticable airseal between cylinder, piston, and nozzle, the gears had to much clearance, and the whole GB stick's under the bleu Chinese grease !

 

  • So the Cylinder was internaly polished  
  • original Cyma piston replaced by another bleu plastic one (also a one teeth version but i dont shoot much anyway)
  • Cyma flat piston head replaced by a silent Element piston head
  • O-ring stretched until a decent airseal
  • Plastic Cyma clinderhead (was way to lose) replaced by a Element brass head, (with some extra Loctite sealant )
  • Cyma plastic nozzle replaced by a  SHS red , length's seem be exact the same  default_smile.png
  • Gears shimmed
  • Gearbox cleaned and re-greased with "real" SKF bearing grease,  Element "airseal grease"

EDiPr8J.jpg

iID9fDd.jpg

fq1FNDe.jpg

v9GYz8Z.jpg

TekPz4R.jpg

 

So far so good, more soon so stay tuned , and hit the "follow" button ! default_wink.png

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Simply fantastic!

 

Hope you will make fully custom airsoft guns too in the future.

 

For example AR-10 (I mean the older 7.62 variant of AR-15), or some else rare rifles, which don't have, and maybe never will have airsoft version.

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