This might sound foolish though I have heard several versions of answers.

What is the correct  method to determine the barrel length on a Bushmaster XM15 ES2 H-Bar or a Colt AR-15? How should measurements be made?

Charles in Maine
www.techantiques.com

With the action closed, drop a cleaning rod down the barrel and mark the point on the rod even with the end of the barrel (or permanently attached brake).

Measure the cleaning rod to the point you marked. That's your barrel length.

Barrel length is measured with a rod down the bore to the face of a closed bolt with the rifle [u]cocked[/u] (so any firing pin protrusion doesn't shorten the barrel).  Dave describes how to do it.

Don't expect a 20" bbl to measure 20.0000000".

Revolvers are an exception the this, which is why short barrelled revolvers have much more muzzle velocity than the "same length" barrel in an automatic pistol -- an apples to oranges comparison because one includes the chamber and one doesn't.

-- Chuck

Whoa nelly!!

I have personally had my barrels measured several times by LEO's hoping to imprison me for a few millimeters too little barrel.

Those lousy bitches measured from the FORWARD EDGE OF THE RECEIVER to the furthest permenantly attached part of the barrel.

16.1", or 18.2", most every time...unless the Cop In Question wasn't bright enough to figure out how to run a tape measure, in which case the damn barrelslook longer than they are to him! HA!!! Good candidates for Nightstick-Only status, huh.

Regards,

FastVFR

That may be the way those LEO's did it, but the way we've been discussing is the way the ATF does it.

THat's how i was told....drop a rod down the barrel. That's how most LEO's and AFT measures it. Useless bit of info: According to the Wisconsin DNR, they measure barrel length from the muzzle to the firing pin.