I'm overseas but have been purchasing the parts to build a "long carbine" of sorts.

I'm putting together what has been seen in the wild as an A2 fitted with an M4 buttstock and KAC M5 handguard.

I grew up with the M16 and later the A2 and have always appreciated 20" rifles, but the adjustable stock is a nice capability.  I'm fitting it with the KAC handguard so I can mount a light and a stubby grip.

I do appreciate the function of optics, both magnified and not, but there's something to be said for sights capable of doing some distance work that never need batteries.

In the meantime, I'd love to see some pics if anybody has done similar builds.

I saw several of these style configurations when I was in KAF going to and from my FOB. Got a chance to handle one once, mainly because person whose weapon it was started to walk off without it from the dining hall I was eating at. It felt nice before I threw it at said private and hemmed him up for leaving his weapon unsecured at a table by itself without a friend to watch it

So it had a 20" barrel and collapsable stock but was a service rifle? Interesting....

Yes there is another member on here who should be chming in and showing the picture he has of one meeting those specs and also sporting a M68 on the kac rails

There was a kit that they had to make A2s have adjustable buttstocks for some units. I found out when I was my company armorer and talking to other armorer's and  people at KAF

Damn thats crazy bro. I definitely want to see pictures of this

Here are some pics of some M16A2's that my students drew from the weapons pool at Fort Sill. Some of these had M4 stocks.

That is such a strange sight to see. Thanks for posting!

I just finished BCT and that's what I was issued. At first I was pissed because it was goofy as hell, but it actually worked out nice. Not a bad combination.

The "Hybrid Buttstock Kits" come with an "H6" buffer which is roughly the same weight as the "H3," IIRC, but has six smaller reciprocating tungsten weights rather than a normal buffer's three weights.  

This is supposed to be for improved reliability with the short receiver extension and 20" rifle length gas combination, however some photos of M16A2s with these "Hybrid Buttstock" kits installed appear to have H2 buffers installed.  

M16 Buttstock Kit, NSN: 1005-01-569-6938, P/N: 13023910; H6 Buffer Assembly P/N: 13023911

H6 Buffer Kit at Damage Industries

~Augee

Thanks for that link Augee, definitely going to be purchasing one of those kits in the future

If I end up going with this configuration, I'm just going to use a plain old H3 buffer (for cost reasons). In semi auto it should, in theory, work just fine.  I also have an H buffer on hand if I experience issues with weak loads.

I am really curious about is the handling of this configuration.  I'm thinking of dropping M5 rails on it, but worry that it might be noticeably front heavy.  I have considered going with Fulton Armory's rendition of a Cav Arms C1 buttstock as a happy medium, in lieu of the M4 stock.  I've even thought about having the barrel cut to 18 or so inches.

I just really want an A2 style rifle, but am certain that I don't want the length of the standard A2 type stock.  It seems that a carbine with an M4 stock or Fulton's C1 stock, and with the barrel cut to 18.25" or so, would make for a nice handling gun.  Even with the M5 RAS, the slightly shorter barrel and the additional weight of the C1 stock could balance things out nicely.

I would look very seriously into a "Dissipater" style configuration with an A1 (C1) length stock if you're not married to a particular configuration and/or barrel weight.  

~Augee

I've already got the 20" barrel, so sticking with a rifle gas configuration is what is leading me to consider getting it cut to 18".  From what I've gleaned from some web searches, there is a negligible loss in velocity with an 18" barrel (as compared to 20"), so that is an attractive factor.  It does seem however that lopping off 2" of that thick portion of the barrel might change the handling characteristics quite a bit.  

I've got a spare M4 stock and 4 pos extension, but I'm not married to that component.  For $100 I can easily switch gears to the C1 stock (with upgraded hardware as offered by Fulton).

There are a lot of guys, particularly in the Retro forum (but not limited to) that have had good success using the "605" barrel configuration of a rifle length gas system and a ~16" barrel - judging by your location, I suspect that you're not going to have too much trouble with operating the weapon at the extreme end of its operating envelope in artic conditions where the rifle length gas system and ~16" barrel might cause you problems.  

There's a lot more knowledge, experience, and various different parts available these days to "tune" such a configuration than there were in the early 60s to make it work, and as I've said, there's more than one guy whose gotten it to work pretty well.

The only other comment I might have on that point is that if you have a USGI factory 20" M16A2 barrel, it might be worthwhile and very well of you to try to sell/trade it to someone whose trying to piece together a USGI M16A2 clone, as authentic barrels are getting rarer and rarer and more and more expensive.  If it's an aftermarket, on the other hand - chop away.  

~Augee

Here you go OP. I took a pic of my A4 type upper on a M4 lower off of one of my carbines.  I had this upper on this lower a couple years ago until my full buttstock came in.

Do I like this configuration? Yes I do, very much. I'm kind of short and that being said my arms are too. Not having a buttstock makes the length of pull a lot easier, it makes that whole package a lot more handy all around. I'm currently building a A2 rifle clone, my buttstock may go to it and go to the VLTOR A5 system (if I can afford the damn thing.)

Also, when this upper was on this lower, I didn't have any experience that made me believe I needed a heavier buffer at all. It cycled just fine.

See that looks awesome. Looks like it was meant to be. The A2's with m4 stocks looked a little funny to me

I'm taking your advise and going to try to trade my barrel for a CHF PSA barrel or something similar, for the builders looking for original stuff.

I've built some period correct clones myself (GUU-5/P with light and M4 type barrel as examples), and can appreciate the build value of genuine components.

16" A2 w rifle gas and cav C1 stock for reference.

Not strictly speaking an A2 because it has a flat top upper, but it does have a 20" government profile barrel, rail handguard, collapsible stock and sights that never need batteries...



BCM KMR 20" upper
BCM carbine lower with B5 SOPMOD Bravo stock
ACOG TA31RCO
Troy BUIS's
Surefire Mini-Scout light in a Haley keymod offset mount, with SR tapeswitch
Vickers sling (not on yet when I took the picture)

Anyway, a lot of people apparently think a 20" upper on a carbine lower is goofy, but I'm not one of them.

I don't think it would be too front heavy if it's a govt profile 20"er.  My recce upper weighs more than a 20" a2 govt.  Heck almost any m4 with stuff hanging off the front is going to be more front heavy.  Now if you start hanging all kinds of stuff on the barrel it might feel front heavy too.  But not much more than an m4.  Especially an m4 with a grenade launcher attachment.

I've decided to do the proper thing and get both, so to speak.

I'm going with a somewhat traditional A2 build, the buttstock being the one real exception.  I've decided to use Fulton's upgraded Cav Arms C1 for the slightly shorter A1 LOP.

Other than that it's NOS Colt A2 handguards, NOS non-F marked FNMI A2 barrel, McKay lower, etc.

For my long carbine build, I've decided to go with a slightly updated take on an an A4.  I have an M5 RAS, but I think I'm going to sell those and go with a MI Keymod rail for the weight savings (to avoid it becoming unnecessarily front heavy).  I'm putting an Aimpoint Comp M2 on it (with a Matech buis), and for a stock I'm going to go with a B5 SOPMOD.

I have a Colt 4-pos M4 stock that I'm going to drop on it just to get it built, but figure with the lighter MI rails and in eventually replacing the m4 stock with the heavier SOPMOD stock (along with H3 buffer), it should balance well.

Anyway, when I get back and get the A2 assembled, I'll be certain to post pics here.  I'll reserve the pics of my long carbine for another forum

I appreciate the advice from those who posted, and look forward to a walk down memory lane with a pretty darn close A2 clone.

Looking forward to seeing it!!  

A1 stocks are niiiiiiice.  I don't really mind the A2, as long as I don't have a lot of clothes on or a big heavy jacket.  It does start to get long then.  I have no clue how those guys do it with body armour on.  Now if you're a bigger guy, probably no big deal.  But....

Always thought a Diemaco C7'ish with a 20" pencil barrel on a flattop upper w/M4 lower with a Trij RX06 and a carry-handle backup would have a lot of merit for a shtf weapon.