I've got a 308 build in progress and wanted some input on a polygonal barrel vs.  standard rifling.
Thanks for any input!

Glocks come with polygonal rifling so you can't trace teh bullet.

http://www.ar15.com/forums/f_6/5_Precision_Rifles.html

Polygonal provides better gas seal, less bullet deformation. Also they are supposed to last longer. I read where most barrel makers wouldn't use polygonal because of this. It would cut their business down by half. This was a quote by stock maker Gale McMillan years ago.

Here it is:

Subject: Re: polygonal rifling
From: Gale McMillan <" gale"@mcmfamily.com>
Date: Apr 23 1997
Newsgroups: rec.guns

Barry S Brummett wrote:

# What does "polygonal rifling" mean?  How is it different from other
# kinds?  Is it  a process or a pattern or what?  Thanks in advance.

Instead of the rifling being square and hanging down in the bore so that
it can engrave a square notch in the bullet it has flats where the
rifling would be.  The bullet is not upset much.  Instead of having 6 or
8 sharp knotches it will have small flats that are very unnoticeable.
This makes the bullet fly better in the wind because there is no sharp
edges to bite into a cross wind. The bullet jacket is not deformed as
much so the chances of loose cores are much less.  Since there is no
sharp corners to burn off the barrel life is much longer and is
dependent on heat checking alone to end its life.  That is one major
reason most barrel makers are not interested in them.  It would decrease
their business by half.  They are more difficult to make than regular
rifled barrels for a couple of reasons one being they are difficult to
lap and give a cut barrel maker more problems due to tooling.

Gale McMillan

It really depends on the barrel and the barrel maker.  For example, Schneider makes polygonal barrels.  They are known for their speed and accuracy, but they suffer for short life due to the softness of the metal.  Generally, precision rifle shooters tend to run cut rifled barrels from Bartlein, Krieger, Brux, or Rock River.  In the button barreled category, it would be very hard to get away from Shilen, their reputation is stellar and every one of their barrels that I have had have shot very well and lasted longer than they should.

I was looking at barrels from Black Hole Weaponry.
link