I am in the process of have a 280ai built on a 700 action. I'm a little unsure of which barrel contour to use. I am trying to keep this gun as light as possible. My concerns are do I go with the #3 sporter in favor of weight or do I go with the #4 sporter in an effort to be able to fireform more brass without the barrel heating up too much too fast? I'm using a 25" barrel and the weight difference will be around 6oz (give or take). I know I can always make up the 6oz somewhere else (light weight scope mounts, ect). Will there be any potential accuracy increase with the #4? It will be used primarily for a big game gun, not a p-dog gun.
Thanks

I have have several rifles that must have the brass formed. For my big game rifles I will make up 50 cases. Gives me plenty for load development and a full MTM box for the trip. I often use the Chreme Of Wheat method. But, even with full loads it doesn't take long to do them all. Or just take a few each time you go to the range. I would save the 6oz from the barrel as well as cut another 6 oz somewhere else if the rifle is to be a carry. I used to carry a 10#+ rifle in the mountains and then built a 6.5# one. I will never go back to heavy. I keep the heavy ones for stand hunting.
Just my two cents.

I have a no 3 Douglas x barrel in 240 wby mag, and it is not quite as light as a true sporter. I would opt for the no 3 over the 4 if this is a hunting rifle.

If you are trying to keep your rifle as light as possible, you will have to use the lighter barrel. You may make some up on other parts of the rifle, but you can do the same with the lighter barrel. As far as overheating the barrel, just shoot slower. The amount of time you spend fireforming cases is a lot less than the amount of time you will spend carrying the rifle when hunting. Seems to me anyway.

See also this discussion about barrel contours, there are arguments from both sides of the fence ("The Heavies" vs. "The Thinnies" ):

AR Barrel Contour Discussion

Note the links contained in above discussion to other website where Charlie Sisk also provided his input on this matter.

- mike