Does the book "The Black Rifle" provide any info on the diameter of the very early prototype barrels?  Specifically, I'm trying to find out the diamater of the barrel between the front sight base and the muzzle.

Thanks for your time,
John Thomas

from Ekie's Guide tacked at the top of the page:

Colt had no rifle barrel manufacturing capability at the time that the Colt/ArmaLite Model 601 into production in December of 1959. Model 601 barrels were made by Winchester, six groove, 1/14, and broach cut. These barrels were originally turned down to app. .565" in front of the front sight base.

I believe he's asking about the original ArmaLite prototype barrels and not the 601 barrels.

The proto barrels barrels are of a different contour than the Colt/Winchester barrels and are much thinner at the muzzle end. While TBR does not specify dimension (unless I missed it), I'd wager they're in the .400" range or so. If the barrel under the front sight is the "standard" .625 then, they taper down to near half that diameter and I can't imagine them being as thin as .300". The very early barrels were also a bit thicker, and fluted, under the hand guards.

I can try and work up some rough comparison drawings of the contours and dimensions after work but, I don't have a lot of tools or sophisticated computer software to work with so, they'd be quite crude.

57Octane,

You are right, I'm asking about the original ArmaLite prototype barrels, not the 601 barrels.  I

If you think you can come up with a ballpark from using the contours and some known dimensions, that would be much appreciated; even if the info is crude.  Thanks for the offer to help.

John Thomas

Alright, from my A1 clone, pictures I have collected, pictures in the black rifle, and my best guesses, this is what I've come up with. They are the same length (they're not perfectly aligned in the picture but, trust me, they are the same) but, the contours and profiles are different as you can tell.

The diameter I came up with was about 5/8 (.625) for the area under the gas block and directly behind the muzzle threads. It tapers down to 7/16 (.437). I kept the tapers themselves about 1/4 of an inch in length. The barrel in front of the sight is about 7 inches long because of how the sight is positioned on the prototypes. That's what gives it the illusion of being longer than 20in. The area under the handguard is about 3/4 (.750) and it is according to TBR, fluted from the gas block to the taper of the chamber. The area under the hand guards may need a bit more refinement but, it's close from what I can recall.

Again, these are pretty rough but, should help those of us working on prototypes to get a good footing.

Outstanding information.  Thanks very much for your work on this.

John Thomas

Glad to be of help.