S&T/AGM MG42 externals help

Funny you should ask about this

As your aware,to transform an MG42 into an MG3 you will have to purchase RS MG3 parts.In the building of mine,I used RTGPARTS exclusively.A link is here:

https://www.robertrtg.com/store/pc/MG42-MG3-M53-c17.htm

My goal was to build as convincingly as possible,an MG3KWS.This is the assault variant of the MG3 and is offered as a retrofit kit by Rheinmetall to transform any MG3 into the KWS.The kit includes the following:

Stock with cheek riser
picatinny rails for the barrel shroud
monopod for the stock
scope and mount
select fire trigger group
and the parts necessary to slow the rifles ROF down from 1200 rpm to 600 rpm.

In the building of mine I used the following MG3 parts:

MG3 muzzle booster
" top cover
" feed tray
" 50rd assault drum
" cocking handle
" top cover hinge pin
" barrel gate
" rear sight

Other parts were also used,and I'll get into those as we move along.

To get started I'll start with the hardest part of the build as thats how I go about doing them anyway,the feed tray.Quite alot of the external MG3 parts are made from stamped steel.The airsoft MG42 version while being very convincing is slightly off spec in regards to measurements of this part of the rifle.On the front of the MG42 feed tray,the steel is vertical and makes a fairly sharp 45 degree bend to cover the top of the GB and chamber.The MG3 feed tray being made of much better steel that has been pressed does not.

This resulted in the MG3 feed tray not sitting squarely in its slot on top of the rifle chassis.It could be used of course,after a hole is cut into it giving you access to the chamber for the drum feeding block.Being a stickler for detail I went a completely different route.I chose to keep the Hinge half of the MG42 feed tray,and incorporate into it the drum mount of the MG3 feed tray.Thusly:

You will need to measure the original MG42 feed tray width.The portion of the MG42 tray the drum mag feeding block drops into has to stay on the part of the 42 tray so you can feed it.The balance of the missing tray is made up for in the MG3 tray.Cut both,grind smooth,weld together,repeat grinding until smooth.

Before you get into any of that,put a magnet on your MG42 feed tray to make sure its made of steel.If its not your going to have to use the MG3 tray and do alot of cutting.Doing it the way I did,I came up with this:

Uller said:

And so it begins.I dont know the exact manufacturer of my base rifle,as it was branded "Matrix" by Evike and I bought it second hand.So your muzzle booster issue will require me to see several pics,from several angles to give you any advice for removal.Mine simply unscrewed.As you know the MG42 muzzle booster is quite a bit different than the MG3 booster.Ill be doing these posts in blocks to make it easier on me,and easier to read.Expect them to be fairly pic intensive as I tried to chronicle the build as best I could.So,lets move on.

Click to expand...

Here are some images of what mine looks like, I pre-ordered mine from evike when they were first released, my assumption was that this is possibly an older model and that the newer version has an easier to remove flash hider. I also planned on buying another MG42 anyways, just so that I can keep both the 42 and the MG3.

Next came the drum mag conversion.The HK made 50rd assault drum opens by simply pushing down on the handle,and the hole outside of it rotates on the side that is latched to the gun.You will have to take it apart to make the necessary brackets to house the feed mech from the MG42 drum.

I bought pvc sheet from Amazon as my building material and cut and bent it for my bracketry.Because the drum is made of plastic,I used pvc cement to afix the bracketry to the drum.I used a butane torch and a vise to make the square,right angle bends in the pvc.The drum as it is holds as much as an M4 high cap I would guess.But,because of the way it opens,and because it doesnt need to be removed from the gun to reload,reloading takes mere seconds.I could live with the trade off.

In the pic the ammo capacity look quite a bit limited to the original capacity of the 42 drum,and it is.This is because I chose to house the battery in the bottom of the drum.The battery space in the chassis of the rifle was far too limited for me.It is in the drum actually.To supply the rifle with the amount of power I wanted I chose to make a harness to run two small 1500 mah 11.1v lipos in parallel.This doubles there MAH rating but maintains there 11.1v rating.You will need to get a new feed tube spring and cut it to length.Retro Arms makes them and are easy to find.The wiring and mosfet installation ill leave for you to figure out.Not hard to do.No sense in giving everything away.

The feed tray.When you get the RS MG3 feed tray it has part of the belt feed mech attached to the bottom side of it.You could go ahead and keep it on there but I strongly advise against it.The belt feed mech just adds weight to an already fairly heavy piece of the rifle.All that weight is resting on the top cover hinge pin,and that is being born by your trunion which is not steel.

For the life of me I cant remember how I removed it.I can tell you it was a PITA.After you get it removed,and before you actually mount the top cover,you will want to flip it over and grind down the inside of the bottom of the latch that closes over the top of the chassis.This latch is made of hard steel.If you dont the latch will slowly eat the part of the chassis intended to hold the top cover down at.

Im truly sorry man,I have no pics of this.Thinking about it I cant believe I dont as I took pics of damn near everything else,lol.When you get to that point you will quickly figure out what I'm talking about.

After you get the top cover seating all figured out its time to remove it and work on the bracket you'll need to mount a rail on top of the cover for an optic.

The top cover has a weldment pretty much centered on top of it for the covers hinges.I used pics of the RS MG3KWS to get the placement of mine where I wanted as far as how far forward it should go.
I centered and drilled a hole in the weldment,then centered and drilled a hole in the rail I wanted to use.After the I lined both holes up and measured the total depth of both holes combined.Next I chose a bolt with the correct length I needed,clamped both parts together exactly,and used a tap to thread both at the same time.I then attached both parts together from the bottom side of the top cover with my bolt tightly.

After that was done I placed a small torpedo level on top of the rail and leveled the rail out.I used a piece of 1/2" alluminum plate for my bracket to support this rail.I simply placed it next to the leveled top rail and scribed a line on the side of it.After that I cut it,made sure it all the corners were square on it,then installed it underneath the toprail and clamped it down hard.

Measuring the position of the support from the top,I was able to figure out where to drill on the bottom side for the retaining bolts.I did this and tapped like I did for the front.To hold the rail down on top of the support,I drilled into the valleys of the rail lugs and used set screws to hold it down.