G&G CM 16 Mod 0, Inner & Outer barrel change

[Lothrian]

Hi, I'm looking into changing the whole front end of my CM 16 Mod 0, I would like to create a LMG/ rifle hybrid for myself.

The gun is currently stock out of the box, well used but well maintained. 

I have been looking at the components for a while and do not know what I need to get, the measurements are confusing.

I am looking for;

Inner barrel

Outer barrel

RIS/RAS Handguard

Flash hider/Suppressor (barrel ext).

I'm a little lost, please help.

this is my first attempt at converting it, only done the maintenance work so far. strip down & reassembly is not a problem.

No photos at of yet. I will try to get some when I am able, its well and truly packed away at the moment

 

[Lozart]

I have been looking at the components for a while and do not know what I need to get, the measurements are confusing.

Which measurements exactly?

 

[Lothrian]

What inner barrel length goes with what hand guards and outer barrels?

 

[Lozart]

What inner barrel length goes with what hand guards and outer barrels?

OK, you're going to have to give us a starter for 10 here.

What have you been looking at for inspiration, maybe we can start there?

 

[Lothrian]

What I have is the basic sloppy inner barrel G&G supply, I don't want to stray too far from the basic m4/ar15 size or shape.

I would like to put in a tighter barrel (6.03) maybe a little longer if I have the cylinder capacity.

Key changes I would like to make is to remove the plastic (no rail) handguard, and replace with a 4 side RIS/RAS, not sure which one yet.

Due to hop up location how much longer/shorter does the inner barrel have to be than the outer barrel?

What length handguards will fit what length outer barrels (so I can decide what I like and where to spend my blood sweat and tears), i.e. 7", 10", etc.

I don't really know where to start after that.

I play as a rifleman, not specialist, but having the ability to quickly switch from rilfeman to support gunner with a mag switch and bipod fitted to rail could be the difference the team would need at a critical point.  Mag and bipod will be held in my vest pouches during battle sim ready for a fast switch.

Am I being a moron by missing the obvious, I hope not

 

[Lozart]

What I have is the basic sloppy inner barrel G&G supply, I don't want to stray too far from the basic m4/ar15 size or shape.

I would like to put in a tighter barrel (6.03) maybe a little longer if I have the cylinder capacity.

Key changes I would like to make is to remove the plastic (no rail) handguard, and replace with a 4 side RIS/RAS, not sure which one yet.

Due to hop up location how much longer/shorter does the inner barrel have to be than the outer barrel?

What length handguards will fit what length outer barrels (so I can decide what I like and where to spend my blood sweat and tears), i.e. 7", 10", etc.

I don't really know where to start after that.

I play as a rifleman, not specialist, but having the ability to quickly switch from rilfeman to support gunner with a mag switch and bipod fitted to rail could be the difference the team would need at a critical point.  Mag and bipod will be held in my vest pouches during battle sim ready for a fast switch.

Am I being a moron by missing the obvious, I hope not

It's a complex and daunting world to the uninitiated so no, you're not being a moron!

From the G&G website: http://www.guay2.com/en/product/detail-17

That states you have a 330mm inner barrel so that or as near as dammit is the length you want to go for with your current outer barrel. I'd suggest this one (when he's got some more in stock) https://www.ak2m4.co.uk/internal-parts/inner-barrels/zci-inner-barrel-300mm or this one https://www.ak2m4.co.uk/internal-parts/inner-barrels/zci-inner-barrel-340mm if you're happy to go with a suppressor to hide the end. Usually the front end of the inner barrel will sit at the end of the outer barrel (ie not stick out into the flash hider). a 300mm barrel will work with an outer down to 10" (for your MK18 style guns) but will make little to no appreciable difference to accuracy compared to the longer one. Basically you're looking at the inner barrel being roughly an inch or two longer than your outer barrel.

As far as handguards go, it very much depends on the style you want. The old M4 RIS/RAS rails were 7" and are clamped between the delta ring (the spring loaded bit at the body end of the barrel) and the end cap (attached to the back of the front sight post). You will need to measure the handguard you have on now as it looks like it won't be a straight swap unless you want to change the outer to something a bit more standard.

In terms of lengths, a standard M4A1 has a 14." outer barrel and a 363mm inner barrel. In a standard M4A1 configuration the handguard would be 7" for a drop in style as mentioned above or if you remove the front sight post and go for a "free float" style that is only attached at the receiver end then you can have any length you like up to the length of your outer (although usually stopping short of the flash hider to allow for attaching suppressors etc). 

If you want to stick with your current handguard but have it be a bit more useful, look for "MOE" style rail sections as they should bolt onto the slots on your handguard allowing you to attach a bipod.

Hope that helps!

 

[Lothrian]

That's great, thanks.

I have done shimming and general maintenance but this is my first attempt at the pretty externals.

Probably diving in at the deep end but that's how you learn to swim the fastest right?

How does a "free float" work?

I know the front sight post on the CM16 Mod 0 will undo with an allen key so I can more/remove it if I wanted.

 

[Lozart]

How does a "free float" work?

As I said above, old school handguards are secured at both ends, a free floating guard is only attached at the receiver. Basically you replace the delta ring with a new nut that allows the guard to clamp to it.

Some of the newer style ones literally clamp around the receiver nut like a jubilee clip (like the lovely Centurion Arms CMR rails https://www.ptssyndicate.com/products/pts-centurion-arms-m-lok-cmr-9-5), others (like the old Daniel Defence MK18 ones) have a section behind the receiver nut that the front bit is bolted to with screws like this:

Quad rails like the Daniel Defence ones are considered a bit "old hat" these days and keymod or M-Lok have become the new things to have. There's a lot more keymod out there but M-Lok is demonstrably better (in the real world at least, not sure if airsoft manufacturing materials make much difference to be honest!). EIther way, they're a lot lighter and more hand friendly to hold onto so unless you specifically want that quad rail look, go for one of the new ones.

 

[Slamz]

Lozart has given some great advise, but just to add. If you change the outer barrel, you'll need a new barrel nut as the standard delta ring is too small on the CM16 for most m4 barrels as G&G use a 2 piece outer barrel. So your easiest option is to buy a new outer barrel and a free float handguard/rail system that comes with a new barrel nut. 

Obviously you could increase the ID of the delta ring if you're handy with a dremel, but if you're losing the front site, you can't use the clip in handguard anyway. 

I researched quite extensively upgrading my CM16, and due to the cost, I ended up just buying a new rifle that fit the style I wanted 

 

[Gepard]

I have this model of CM16 and underwent a similar process with upgrading it and swapping out the furniture. The finished product was this - 

Is the style something you're after? If so I can share the part list and the process if it would help. 

View attachment 33581

I can tell you that if you're wanting to swap out the handguard you'll need a new outer barrel. The one fitted to the Mod 0 is only really compatible with the fake MagPul furniture it got shipped with. As the barrel shortens towards the mid there is no place to drill a new hole for the pins on the front sight. 

There is a possibility you'll need a new delta ring assembly as well, so just bear that in mind when choosing your new handguard. Two piece ones such as the MagPul pictured above will fit fine, but not the railed ones. The spikes on the nut are too tall resulting in the top piece of the handguard not fitting correctly. 

 

[Lothrian]

Thanks guys. This is great info.

@Gepard, if you got give me that list it would be great.

I think that is the endish goal for the core rifle.

 

[Gepard]

@Gepard, if you got give me that list it would be great.

My setup isn't perfect. I did have to do a bit of filing for a clean fit. That's the problem with mix and matching from multiple brands. Hope it helps either way. 

The handguard is a CYMA M014 - you'll need a new delta ring assembly to fit it. 

The outer barrel is a Z-Parts 14.5inch. 

The flash hider is an Iron Airsoft birdcage style.

You'll also need a new gas tube to accommodate the shortened length of the handguard. 

Certainly not going to be a cheap process hence why I doubt I'll ever sell my M4 - it's only a CM16 after all. 

 

[Lothrian]

Gas tube being non functional and for locating purposes can be "made" quite easily so I dont think that will be too much of a problem.

My trade will assist with jigary pokary required for perfect fit up, might have to accidently slip at work, "oh no, how did that just fall in to the cnc machine and begin a program" 

?