AR-15 A2/A4s

[FireBirdDS]

It seems in recent years, the classic 20” mil-spec AR-15 A2/A4 model has experienced renewed interest, with manufacturers like Aero (among others) offering complete 20” A2/A4 uppers complete with detachable carry handle rear sight.


I’ve even seen complete Colt 20” models on the shelf of my local gun store as part of regular inventory at a (shockingly) reasonable price.

Is this (seeming) resurgence pure nostalgia? I was under the impression shorter is better for most practical purposes. Are the 20” A2/A4s once again practical/tactical? A little of both?

I’m tempted to buy one purely because it’s hard to beat the original look aesthetically.

 

[Ark]

M U S K E T

 

[edwea]

M U S K E T

 

[cosermann]

20” barrels generate higher velocities than shorter barrels.

So, for bullets that depend on fragmentation for most of their lethality, bullets fired from longer barrels travel farther before slowing below their fragmentation threshold than those fired from shorter-barreled rifles, and thus have a greater effective range.

The difference is about 40m to 50m respectively for M193 and M855 loads when going from 16” to 20” barrels where the fragmentation threshold is about 2700fps.

As an example, if you want to reach out to 200m with M193, and you want it to reliably fragment at that distance, a 20” barrel is the way to go, since M193 drops below 2700fps around 140-150m when fired from a 16” bbl.

Modern, barrier blind expanding bullet designs change things a bit, of course.

 

[Ark]

20” barrels generate higher velocities than shorter barrels.

So, for bullets that depend on fragmentation for most of their lethality, bullets fired from longer barrels travel farther before slowing below their fragmentation threshold than those fired from shorter-barreled rifles, and thus have a greater effective range.

The difference is about 40m to 50m respectively for M193 and M855 loads when going from 16” to 20” barrels where the fragmentation threshold is about 2700fps.

As an example, if you want to reach out to 200m with M193, and you want it to reliably fragment at that distance, a 20” barrel is the way to go, since M193 drops below 2700fps around 140-150m when fired from a 16” bbl.

Modern, barrier blind expanding bullet designs change things a bit, of course.

M193 at full throttle out of a full length barrel has also been known to defeat some intermediate, special threat, and generally cut rate body armor. Most notoriously, cheap steel plates of the variety sold by AR500.

 

[BigMoose]

The 20 AR inch is the definitive 5.56 rifle, for most of us in the civilian world. It is what we should be using.

5.56 is very velocity dependent. When you look at barrel lengths, vrs the velocity. The optimal barrel length is usually in the 24 to 26 range.

So by using the 20 inch barrel, you will often gain a lot more FPS on a cartridge that honestly depends on velocity to be effective.

The only reason the carbines exist is because of Vehicles and they are easier to carry all day. Things none of us do on a regular basis.

The other benefit is the rifle gas system, and the rifle buffer is bar none, the softer shooting setup. The 20 inch AR is the kind of thing you can hand to your sister, and have them say, "There is hardly any recoil"

The rifle gas and buffer are also more tolerant of a wider range of ammo specs, and there is no buffer weight tuning to do. There has only ever been one rifle buffer weight. Its the same thing that has been used since the 60s. (yes I realize that VERY VERY early AR rifles had a different buffer, but you will likely never run into it)

 

[Dean C.]

It seems in recent years, the classic 20” mil-spec AR-15 A2/A4 model has experienced renewed interest, with manufacturers like Aero (among others) offering complete 20” A2/A4 uppers complete with detachable carry handle rear sight.
View attachment 290595 View attachment 290596

I’ve even seen complete Colt 20” models on the shelf of my local gun store as part of regular inventory at a (shockingly) reasonable price.

Is this (seeming) resurgence pure nostalgia? I was under the impression shorter is better for most practical purposes. Are the 20” A2/A4s once again practical/tactical? A little of both?

I’m tempted to buy one purely because it’s hard to beat the original look aesthetically.

Nostalgia resurgence, a lot of guys who served when the A4/A2 were issues have disposable cash and want their "old gun". Also Modern Musket is refered to as the M16A4 flat-top with ACOG IMHO and it's called that due to the fact that all 55gr ammo out of a 20in barrel is basically level 3 armor killers. The ballistics really are outstanding if you can deal with the extra length.

 

[Dog1]

If you're going to do the 20-in A2 musket, do not do the bastard version with the detachable carry handle. Do it right. And if you're going to do it right get a clone M16A2 lower from Palmetto State Armory to complete the package.

 

[Scott58]

Both my AR's are 16". A 20" would be a good addition.

 

[Ark]

View attachment 290618

If you're going to do the 20-in A2 musket, do not do the bastard version with the detachable carry handle. Do it right. And if you're going to do it right get a clone M16A2 lower from Palmetto State Armory to complete the package.

Mine is a Colt ban era A2 upper and a PSA complete lower.

Colt must have run a light buffer on those because I couldn't get it to run without changing the buffer weights for aluminum. God I love that rifle, though.

 

[55fairlane]

All NM (national match) rifles are 20 inch. A 16 inch carbine won't accurately hit the 600 yard target.

It's hard to pass on a Rock River Arms NM ..... or better yes white oak armament or compass lake engineering......

In my opinion areo are lower end

 

[Tombs]

Because the 20" rifle format is the optimal format for the stoner system and the 5.56 cartridge.

 

[Michigan Slim]

My first and only AR is a Colt Match Target. Never saw need of another. Yet. Someday maybe. I built my daughter a Palmetto A4 carbine kit for her truck. Need to upgrade that one.

 

[MrSmitty]

Mine, on the right, my son’s on the left… Mine is like the one I shot in AF basic, so I went with the original, he has the Ruger carbine....well, until the tragic boating accident....

 

[Kirk Freeman]

16 or 14.5 better? Likely for what I want to do, yes.

20 because America? Also yes.

I have my Colt A4s (M6700) sniperery like the Marines did. What did you guys call them, like SAMR or something? ACT trigger, replaced CH, put SIG Bravo 3 on them, say oorah, hit self in head with a pipe, call it a day. One is in DA OD because that makes it cool . . . somehow.

I also have a PSA M16A4 clone. Do not discount it either. The handguards are thicker, have a different feel, but I get 2.5-3 MOA from a bench with COTS 55grainers and about 2 MOA with that Gorilla 69ers that I bought a pile of during 2016-2020.

In fact here is the exact PSA M16A4 I purchased:

 

[Basher]

For a do-it-all carbine, I find either a 14.5” or a 16” is the ideal size as they still retain enough velocity to meet the needs of most folks. More than 99.99% of us will never use an AR in anger, so the shorter, handier carbines are more useful as they’re easier to maneuver at classes and competitions while still being able to get the job done out to ~150m with M193 if the zombies ever do arise. With proper ammo selection, you can extend that distance a significant amount. Accuracy-wise even a 14.5” AR with a quality barrel can make hits to distance far beyond its actual effective (per terminal ballistics) range.

All that having been said, if you want all the velocity, then a 20” is the way to go for sure. Light and smooth recoiling, accurate, and able to punch through all sorts of barriers? Yes please! If close range “social” work isn’t on the menu, I’ll take a 20” all day long!

 

[BigMoose]

Ohh and 20 inch AR's take a bayonet with no fuss and muss.

The A1 type is worth considering too.

Weight of a modern carbine, 20 inch barrel.

 

[Dog1]

 

[natdscott]

View attachment 290618

If you're going to do the 20-in A2 musket, do not do the bastard version with the detachable carry handle. Do it right. And if you're going to do it right get a clone M16A2 lower from Palmetto State Armory to complete the package.

Just remember, if you start talking in absolutes and declaratives, there is almost always be somebody who is more absolute than you.

A lot of gun types might be surprised what a Shooter can do with a detach carry handle A2.

 

[natdscott]

Because the 20" rifle format is the optimal format for the stoner system and the 5.56 cartridge.

Meh. Not really, at least not now.

Sounds good to type it though, doesn't it.