Can you mix upper and lower receivers?

No, combining upper and lower receivers of different brands will make no difference in accuracy whatsoever.

Can you put a pistol length upper on a rifle lower?

If a lower receiver is built into and registered as a pistol first, it can be stripped down and converted into a rifle in the future. Attaching an AR-15 pistol upper assembly with a barrel shorter than 16″ to a rifle lower is also considered an SBR and will get you in trouble without the proper tax stamps in place.

Can you put a shorter barrel on AR-15?

In the states that allow them, as long as you have the tax stamp and documentation to prove it, you can do as you please in a number of regards! With an SBR you can shoulder your gun or fire without shouldering, have your barrel and overall length as short as you like, or use whatever furniture you like.

What makes an AR 15 lower a pistol lower?

An AR-15 pistol is an AR-15 that has a barrel shorter than 16 inches, does not have a stock, and is shorter than 26 inches overall. The lack of a stock defines the AR pistol as a pistol. An AR pistol allows the user to have a barrel shorter than 16 inches, without having to go through the NFA process.

Can I SBR A lower?

If you have a stripped lower receiver you can register it as a SBR with the ATF. When you apply to make a SBR with the ATF you will be using the ATF 5320.1 Application to Make and Register a Firearm or the eForm 1. If the caliber is already engraved on the lower receiver you will use that for your ATF application.

What caliber fits AR-15 lower?

The AR-15 rifles usually comes chambered for either the military cartridge 5.56×45mm or the . 223 Remington. Because of the pressures associated with the 5.56x45mm, it is not advisable to fire 5.56x45mm rounds in an AR-15 marked as . 223 Rem, since this can result in damage to the rifle or injury to the shooter.