Navy receiver on a G3

[Stealthbomber]

The following is a quick (?) guide to bunging an MP5 navy trigger group on a G3.

 

Why would you want to?

The G3 pistol grip is a weak point of the gun, especially if you have a metal body fitted.

Replacement G3 pistol grips aren't available.

It looks the dogs danglies.

 

This is a guide for the MTV generation. Short on text and long on pictures. If you have a question that isn't answered in the text, just ask.

 

 

 

So, I can just, ummm, bung an MP5 trigger group on a G3, right?

 

Erm, nope.

I don't know if the real-steel parts are interchangeable but there's a problem with doing this on the airsoft guns. It's difficult to explain. If you fit the trigger group to the empty G3 shell it'll look like it fits.

The problems start when you try to get the gearbox in. The root cause of the problem is because the G3 and MP5 hop-ups are in different places in the magwell.

 

 

This means the gearbox sits further back in the G3 and means the navy receiver has the pistol grip about half an inch too far forward.

 

So, in short, we need to lengthen the navy receiver by about half an inch.

No worries. Get the hacksaw out.

 

NOTE: I deliberately made the cut at the front for 2 reasons:-

1) To avoid damaging the trademarks.

2) Cos the gearbox doesn't extend that far forward and it means you don't have to make a super job of filing the inside smooth.

 

As it turned out, I had to repaint the entire part so the trademarks got binned anyway. Oh well!

 

 

Having chopped the navy receiver in half you need to figure out exactly how much bodging you need to do.

I did this by screwing the gearbox into the rear part of the gearbox and then fitting the front part into place and seeing where the rear part ended up.

I didn't just measure this. I put sticky-pads on the ruler and fixed it in place so the 2 parts were linked by the ruler and the fit would be perfect.

 

NOTE: This needs to be PERFECT. If the gap is too small then the front receiver pin won't go in when it's finished. If the gap is too big then the gearbox will sit too far back and the nozzle will leak air.

You MUST get this just right.

 

 

Actually, I've got a bit ahead of myself here.

The navy receiver is textured and I wanted the infill I made to be textured too.

To do this I put some plasticine around a large enough area of the receiver and then made a wax cast of the surface.

I'd then place this on the outside of the gap, apply the infill from the inside and, when dry, the external surface would be the same as the rest of the item.

 

This turned out VERY well and is definately worth doing instead of just using a flat surface to control where the infill goes.

 

 

 

Okay, so the navy trigger group is chopped in half and I used something to fix the 2 halves the correct distance apart.

I now stuck the wax plate to the opposite side, mixed up a big dollop of JB Weld and pasted it in.

I should mention that I used a dremel to grind the sides of the join so they were sloped to give a larger area for the JB Weld to stick to.

 

It all got a bit messy here and I couldn't really take pictures while I had JB Weld all over my fingers but, basically, I applied JB Weld to one side then, when it dried, pulled off the wax and repeated the process on the opposite side.

Finally I stuck the wax plate inside the trigger guard and filled the bottom of the join.

 

The final thing to do was join the trigger guard. I didn't bother with the wax for that. I just taped a bit of flat plastic (from a CD cover) inside the trigger guard and then filled the gap with a blob of JB Weld and filed off all the overspill after it had dried.

 

 

For the final part of the modification I had to lop the rear part of the original G3 lower receiver off , chop off the tab on the back of the MP5 grip and glue the G3 one on in its place.

The way to do this is to do it after all the other work is complete.

You need to grind out the inside of the navy receiver a bit and there'll be enough room to fit the G3 part inside because it's thinner.

 

 

The important bit here is to cut off the part with the guide slot in it AND another half inch or so. This will give you an area to bond inside the navy receiver as can be seen above.

I cut the G3 receiver at the rear of the hole where the pistol grip attaches.

 

The other top tip is to get it all ready, apply your glue then slide the trigger group onto the receiver. That way you'll ensure that the trigger group is fitting in line with the receiver and that the rear part is correctly positioned so it is flush with the rear of the receiver.

 

 

I just remembered something else...

At this point you'll find that the G3 stock won't go on far enough. I cut the metal part of the G3 stock just in front of the first pin hole and found that was enough that I barely had to touch the receiver any more.

 

Piece of cake, eh?

 

Now for painting.

 

 

 

There ya go.

 

NOTE: You'll need an MP5 fire selector, selector plate AND selector cam. I used ICS ones as they were the only people selling the selector cam.

 

The trigger group cost about $20 from WGC and the other bits were peanuts, maybe $20 all together.

 

In the end the finished item feels MUCH more solid than the old G3 receiver and it finishes off my MSG90 perfectly.

All in all it was a complete success. If you have a G3 with a damaged pistol grip then this is a decent way to get it working again.

 

 

I used to use Araldite Epoxy resin then, a few years ago, discovered JB Weld and JB Weld is so much better than Araldite for this sort of thing that it's on a different planet.

Half way through this little job I ran out of JB Weld and my local hardware shop didn't have JB Weld any more.

Instead they had a thing called Plastic Padding Super Steel.

This stuff is MUCH better than JB Weld. It dries in 5 minutes AND is a lovely black colour.

If I'd done the whoel job with Super Steel I probably wouldn't have needed to paint the finished item.

 

Buy it!

[Aod]

very very nice.

 

Earlier in the guide, you mentioned that you didn't know whether G3 and MP5 pistol-grips are compatable/interchangable.

 

they are, but you need to change a couple of internal parts (the hammer spring being the most important)

[Panzergraf]

Wow, this is made of win and god, really.

After priming and painting, it really looks like it was made like that from the factory!

 

G&G's MC-51-thingie has a lower reciever like that. It would be my base-gun of choice if I were to do an MSG-90.

[Azulsky]

Actually you can buy G3 lower grips, Warther's Originals on Ebay sells them, just the grip, or it and all the peices($20 for the latter)

They are technically Sar Taktik II Grips by CA but whatever

 

That and if i could figure a way to get the G&G lowers, i would get 4 for all of my babies.

 

This is a great guide though, i might try it on the extra regular bodies i have left over.

 

Stealthbomber you should consolidate all these how to guides into stickies for the Technical section. I see alot of questions get repeated, and we have alot of internet guides we can link to and alot of guys on here who are very knowledgable about this kind of stuff.

[Hvy gear]

Nice guide. Also, G&P G3 grips are avalible at WGC for $21.

[jim_dandy]

You did a very nice job.

[Epyon]

Nice work.

I'd do it with an ICS lower. Since they have the engraved fire selector markings. That way you could keep the markings after paint.

The Navy lower loses something without the markings.

[Stealthbomber]

G&G's MC-51-thingie has a lower reciever like that. It would be my base-gun of choice if I were to do an MSG-90.

<{POST_SNAPBACK}>

Heh!

 

S'funny but I didn't even know that existed. I tend not to look at the retailer websites unless I actually want to buy something.

 

Looking at it, it's got an MSG90 stock as well so that'd save you money too.

[DarkLite]

Nicely done!

 

Pity I loathe the NAVY type grip - my big mitts don't fit them well.

 

Also the selector on the right side of the gun digs into my trigger finger.

[Azulsky]

Couldnt a v3 sit in a mp5 lower, so with this couldnt we get a v3 in a g3

[Stealthbomber]

Couldnt a v3 sit in a mp5 lower, so with this couldnt we get a v3 in a g3

<{POST_SNAPBACK}>

The problem is the length from the nozzle to the motor.

 

On an MP5 the hop-up is near the front of the mag-well so the gearbox sits further forward and the grip can go on.

On a G3 the hop-up is right near the back of the mag so the gearbox sits half an inch further back and, thus, the grip won't go on.

 

If you were designing the gun from scratch you'd take a V2 gearbox attached to a navy trigger group, bung it in the receiver and THAT would tell you how far forward to have the hop-up.

Unfortunately, of course, you can't adjust where the hop-up goes cos then no mags would work with it.

 

In short, the mags dictate the location of the hop-up and the hop-up dictates how far back the gearbox sits.

[HellsAngel]

That's an excellent project you've completed there! Makes your MSG90 look really unique! I love those rifles so much, there definately the most perfected G3 model

 

And I must say... You did an excellent job on the finish of the parts! I don't think I could do such a good job lol

 

+1

 

HellsAngel

[CeruleanSentinel]

I need to get me some of the J-B Weld stuff. I heard it was good for boats. Never thought about airsoft. I have a feeling in the near future...Ill need it. Also, this is a fantastic tutorial!

[Brett230SX]

Stealth,

 

 

Bang up job ol chap! I must say I am most impressed with your fill and casting work. The end result is near out of the mold perfection. An effort of love, for sure!

 

+1

[CeruleanSentinel]

Just so you know, I already have Plastic Padding Super Steel and have recently used it to a crack in a G3 sniper stock. That stuff dries super fast. If you want to do some work like this, it is invaluable. I have also use LocTite, but Plastic Padding Super Steel is that nice tar color, so...yeah.