M4gery Build

Go with the 16" middy with a lighter weight barrel profile. Versatile, lightweight and simple because the muzzle device does not have to be pinned. It will be easy to sell if necessary to raise funds for the SBR. You'll see a greater difference in weight savings by going with a slim profile than you will by lopping off an inch and a half off the length

I agree, 16" mid is the way to go. Much softer shooting and can easily be reconfigured since nothing is pinned.

Plus, if you ever do SBR it, you can sell the middy barrel for more than a pinned 14.7" will bring.

BSW

You say you are interested in light weight, but I get the feeling from your post you are missing the big picture:

barrel profile. A1/A2/M4

Get a true lightweight barrel profile (PSA does them adequately in a lightened A2 variant from FN, ARP does them really well, calls them Scout), Colt makes them in true Lightweight/A1 style. No loss in accuracy unless you are doing mag dumps. Others are starting to catch on - 50 years after it was introduced, of course!

Back on point, look at how much owners of true lightweight Carbines like Colt 6520's, 6720s, love their guns. Aftermarket makers are now getting off the M4forgery trend and on to more practical guns, so it's becoming more available. I also applaud PSA for leading the way with mid-gas on this. ARP, too, though they only really do barrels - albeit great ones with 5r rifling and meloniting. Colts variants are still all carbine gas - but the gas length issue is very secondary in real terms to the barrel profile for practical use.

So if building, look at PSA uppers to get a feel for what can be done with lightweight barrel, or build an upper with an ARP barrel. Possibly find a Colt lightweight upper, though that is hard, people don't part with those.

jr_roosa said:

Quick question to help me plan.

14.5" with pinned vortex or one of the slightly stretched GI style flash hiders. I would start with a carbine gas system and GI handguards, but someday I'd add the Knight's rails for doo dads or even just for looks.

Question 1: How are the Knight's rails? Do they move a ton, or are they relatively solid? I know they're not free floated, but that's not a big deal for me on this rifle...the other build will be the match rifle.

-J.

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Which gen are you talking about? The URX 1&2's are full length quad rails w/ the URX1 having a built-in folding front sight that is actually part of the top rail. The URX3 only has a full length top rail and short rails at both ends of the other sides. They're working on a URX4, but I'm not sure what that will entail.

I have an LPR with the URX3 rail and it is quite solid and very lightweight. I think the URX1 & 2's are quite bullet proof also. The only issue with your plan is that you need a proprietary tool to remove KAC's barrel nut at the tool is ~$200. Unless you know someone with one of these tools, you might as well just buy a complete KAC upper.

jr_roosa said:

14.5" with pinned vortex or one of the slightly stretched GI style flash hiders. I would start with a carbine gas system and GI handguards, but someday I'd add the Knight's rails for doo dads or even just for looks.

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A couple years ago, i discovered a short flash hider and an AAC single chamber muzzle brake. Both extend the barrel about 3/4". They make the 16" barrel very handy and not much longer than 14.5" barrel with a standard flash hider.

The AAC muzzle brake works well but of course the 223 Remington really does not need much braking. The flash hider isn't a GI style if your are looking for the "look".

Unless you have a specific need or desire, not fooling with the SBR paper work can be an advantage.

Just a thought.

Light weight and hanging stuff off rails does not compute!

I'd expect less than a 3 oz difference between the 14.5" and 16" M4 barrels, probably 2 oz.

I agree with the others that a 16" pencil/LW with midlength gas makes more sense than a 16" M4 profile with carbine length gas.

I have the pencil profile from BCM and Daniel Defense and a "lighter profile" from PSA (about 2 oz more than pencil but 2 oz less than government profile. All are 16" middys and all work well. The two pencils of course have .625" gas blocks and the skinny look of the early M16s. The PSA uses the standard .750" gas block but narrows down from there to the muzzle to about .725" (under the handguards it's .625" like both the pencil and govt. This barrel actually is from FN and Spikes also sells it. PSA does sell a true pencil profile too. It's hard to beat the lightweight barrels.

14.5" with a flash hider are ridiculously loud. You are better off with a 16" barrel or even an 18" with a thread protector instead of flash hider. Flash hiders are highly overated and more fashion than function in 90% of most applications. I hunt at night w/o a flash hider and have never blinded myself.

An inch and a half shorter barrel would probably drop less than a half pound. As others have said, barrel profile is much more important. Go for a pencil profile!

adelbridge said:

...You are better off with a 16" barrel or even an 18" with a thread protector instead of flash hider...

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Not so. A buddy had a 16 inch Keltech carbine with a thread protector. It's muzzle blast, especially when fired at an indoor range, was horrendous, even when standing behind the shooter. We put an A2 birdcage on it which focused the blast more down range, making the rifle much more civilized. While flash reduction may not be a high priority to some, it also killed the huge fireball the bare muzzled Keltech was putting out. Since the A2 birdcage is less than $10, it's more than worth it

I added Phantom 5C2 or Vortex flash hiders to my AR rifles. A good muzzle device really does help with the flash problem.

For muzzle concussion I'd rate:

Brake > bare muzzle > flash hider

BSW

For muzzle concussion I'd rate:
Brake > bare muzzle > flash hider

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+1 and Brake > bare muzzle > flash hider >> suppressor

This is one option that should cover most of what you want, if you want to go the light weight route. The midlength version is also in stock should you want to go that route.

If you want to be more "authentic", this would likely be the best option.

I believe the difference between the 14.5" government profile barrel and the 16" lightweight barrel is probably in the neighborhood of 3 ounces. A 14.5" pencil barrel will probably be about 6 ounces lighter than it's government profile brethren.

The difference in handling from a 14.5" to a 16" is not worth welding a muzzle device on, and a 16" middy will be softer shooting anyway. Unless you're sold on the M4 look with the correct amount of barrel protruding, go 16" middy.

I have a Colt AR15A2, 1987 vintage. Screw M4geries, go with the real deal. Oh, and mine is a 1.5 MOA rifle, with irons, and no I'm not tactical and I don't do BUIS and toys.

YMMV, but it shouldn't.

FH

Keep in mind the .223/5.56 caliber lives and dies on high velocity.

The longer the barrel, the more high velocity you get with any load.

There is nothing to be gained in performance with a shorter barrel and a longer flash hider.

Except probably more weight, and cool sorta different look.

The longer pinned or welded on flash hider probably will weigh as much or more then the 16" barrel you cut off to pin on the longer, larger diameter flash hider.

The U.S. Army M4 carbine has a 14.4" barrel, simply because it had to be that length for a U.S. GI M16 Bayonet to fit on the end of it.

It would have been a better combat carbine, with less performance complaints, if it had a 16" barrel and no bayonet capability.

rc