Ernie,
Depnding on whether you are building an open class or hunter class rifle will determine some of your answers. Open class does not have to have a ram rod channel but hunter class does have to have provision for a ram rod. If you are building an open class rifle with a full stock then the shape of the stock should be uniform from the lock mortice to the muzzle. It would not be acceptable to have a shaped fore stock flowing into a flat that could be considered a cant. There does not seem to be a preffered stock shape however a full stock with a wide profile would give you better support on the barrel rest. Hunter class stocks are going to be of traditional style. Many open class rifles do not have a fore stock. Remember that you need to meet the weight requirements for either class.
Mark

I can just see some wag showing up with an open class rifle with a square barrel in order to maximize the bottom flat. At that point I can imagine the rules changing to only allow round or octagonal barrels and to require the ramrod to be in place at the time of firing for hunter class. Always someone looking for a loophole.

Ramrod pipes are sometimes attached directly to the bottom of the barrel. I expect the absence of an underrib would be okay if there's still a ramrod.

Mark
I haven't laughed that hard a while; a square barrel might make for some very interesting harmonics any way I digress. Back to the rulebook where it says traditional hunting or target. I don't recall seeing any traditional hunting, target rifles with square barrels on them. If someone shows up with a square barrel will be sure to go get him a file and tell them to make an octagon. We should probably watch out for the infamous equilateral triangle barrel. I don't recall those being on traditional guns either.

I'm thinking that by the time the season gets underway we will all be on the same page, maybe. I do feel we are getting some good questions, except for the square and triangular barrels, and should have some competitive rifles at the matches.
Mark

robin dont laught to hard yet .you talk about harmonics -well hold on to your hat -volqusin makes a 22 target pistol with a square barrel . my buddies kid shot in jr olympics and uses one now.
dag

Hey Dag
That particular pistol has a couple of things in common with my Smith 22 A it appears that the barrel, square. Indeed, the barrel is a liner, but that being said, have you had a chance to bash your fingers across the Remington with the triangular shaped barrel on but it any rate back to muzzle loading. I love threads like this. It brings up the comedienne and all of us. Richard  Forsythe did make what they referred to as a wide-body think African Zephyr, nobody could ever figure out what it was really supposed to accomplish. Most thought it was a marketing ploy. I think most of them were made in 8 bore and 12 bore. Can you imagine loading up and 8 bore stoking it up with 200 or 300 grains of powder and shooting it from underneath the cover down at friendship. The concussion alone would affect everybody from the silhouette line to the flea market. But hey, I’m open for almost anything once. Talk to you guys later.
Robin