Frequently asked questions
What AR-15 lowers are compatible with the AUTO 20?
The AUTO 20 is designed to fit any standard mil-spec AR-15 lower. No tools, tuning, or modifications are required. Just push two pins and you’re ready to run.
Do I need to change my buffer, spring, or trigger group?
No. The AUTO 20 uses its own internal system and works with your existing AR-15 lower components without adjustment.
Is this semi-auto or pump-action?
The AUTO 20 is a semi-automatic upper receiver. It fires one round per trigger pull, cycles automatically, and resets cleanly.
Can I use my standard AR charging handle or bolt?
No. The AUTO 20 comes with its own proprietary bolt assembly and internal components. Your AR lower stays the same, but the upper is purpose-built.
What’s the barrel construction and choke setup?
The barrel is 16 inches, smoothbore, and threaded for Rem-Choke compatibility. Every unit ships with a standard choke installed, and additional tubes can be used as needed.
Can I use regular 20-gauge shells?
No. The AUTO 20 is designed to run only on Butler Defense’s proprietary polymer-cased 20-gauge shells. These are specifically engineered for clean cycling and safe use in this platform.
Can I reload your shells?
For reloading information, please contact us directly.
Can I use aftermarket AR accessories on the AUTO 20 upper?
Yes. The upper uses standard AR-height Picatinny rails and accepts most free-float handguards and top-mounted optics. You can run your preferred red dot, irons, or other optics with no height mismatch.
How does recoil compare to a 12-gauge or 5.56?
Recoil sits comfortably between the two. It has less kick than a 12-gauge but more satisfying feedback than 5.56. It’s firm, clean, and recovers quickly thanks to the low reciprocating mass.
Is the AUTO 20 good for home defense?
Yes. The 20-gauge platform reduces recoil and overpenetration risk while maintaining serious stopping power. It’s fast, familiar, and easier to control than larger calibers in close quarters.
Does the AUTO 20 count as a firearm?
No. The AUTO 20 is an upper receiver only. It is not serialized and is not considered a firearm under federal law. It attaches to your existing AR-15 lower, which is the serialized part.
Where is the AUTO 20 made?
Every AUTO 20 is hand-built in Sun Valley, Idaho by Butler Defense.
Who designed it?
The AUTO 20 was designed by Larry Butler, a lifelong shooter and engineer who’s been building shotguns for over 30 years. This platform is the result of years of real-world testing and refinement, not a rush-to-market concept.