The Baby AR: How Small is Too Small?

Watching the industry a bit has shown me that there have been two big, but completely separate trends. One is long range guns, with calibers like the 6.5 Creedmoor, and 224 Valkyrie becoming quite popular and the other being smaller is better. Smaller is better applies mostly firearms that are traditionally long guns. This includes SBRs, AR and AK pistols, and weapons like the Mossberg Shockwave. Smaller is better. Today we are going to look at the effectiveness of the littlest of AR 15s, what I’m calling the Baby AR.



Being Specific

When talking about the baby AR I’m not talking about 9mm or 22 LR guns, but ARs that fire the standard 5.56/22 rounds with the shortest, most common barrels out there. As far as I can see the 7.5 inch AR is the shortest you can commonly find. I own a 7.5 inch AR pistol, and I will say it’s a real hoot, but how effective is it as a weapon?


The Baby AR: How Small is Too Small?

Caliber Constraints

The 223 round is based around a 20-inch barrel, and when you start cutting barrel length, you start losing velocity, gaining muzzle flash and concussion. Velocity loss is the most critical when you consider the 223 is a good round because it hits fast and hard. Less velocity means the bullet may not fragment, which causes more damage inside the body. Less speed will also cut your effective fragmentation range down significantly as well. Small Arms Defense Journal did a fantastic analysis of different length AR barrels and the ballistic performance of the standard M855 round.

The Baby AR: How Small is Too Small?

Small Enough to be Shoulder Carried

This study showed ARs with a barrel shorter than 10 inches incapable of reaching beyond a 2500 FPS rating, which decreases the likelihood of effective fragmentation to almost zero. Even at 10.3 or 10.5 inches, the effective range is minimal.


The Baby AR: How Small is Too Small?

As mentioned before the concussion and muzzle flash is a beast when it comes to these super short barrels. It can be blinding and the noise disorientating. The baby AR is a real firebreather.

The Benefits of the Baby AR

There are some benefits to a Baby AR is maneuverability. The smaller the gun, the easier it is to move inside buildings and vehicles with. A super short AR is essentially an SMG that fires rifle rounds. The Baby AR itself is ultra lightweight too. This is helpful for all sorts of long days on the battlefield or at the range. An added benefit of the Baby AR is that it can be broken down at the upper and lower level. Mine fits in my Vertx Commuter with ease. This allows me to carry a compact weapon with a rifle like performance concealed.

The Baby AR: How Small is Too Small?

This Little Guy

Increasing Effectiveness?

Is the Baby AR with its little 7.5-inch barrel worth having? Depending on the application, yes, but there need to be steps taken to improve its performance. Regarding ballistics, I’d suggest rounds that are made for short barrels. Hornady has an SBR load as part of their black line which includes a heavy 75-grain Interlock projectile. Heavier grain rounds don’t get great velocities but do fragment better at lower speeds. Although your range will still be limited.


The Baby AR: How Small is Too Small?

This ammo is also built to minimize blast and concussion. To further reduce blast and concussion a purpose-built muzzle device is needed. Mine wears a Troy Claymore which pushes the blast and concussion forward of the shooter.


The Baby AR: How Small is Too Small?

If you want a useful Baby AR, you should consider a 300 Blackout Upper. The 300 Blackout is a round designed for short barrels and reaches its maximum potential from a 9 inch 300 Blackout barrel. That kind of breaks the idea of a 5.56 baby AR, but it is a simple solution to a severe problem.


I own my Baby AR as just a fun gun. I don’t clear rooms anymore, and my preferred home defense set-up is a shotgun. My baby AR is mainly assembled from scraps and is unique in its own way.  With the right muzzle device and the right ammo, I wouldn’t feel shy about turning it lose.