I'm looking into redoing a sporterized Winchester 1917. I originally thought I'd go 338'06, then it was definitely 6.5'06 AI, now I'm wondering if I should go to a 280 AI.
This rifle will be used primarily for target shooting out to 500 yards for now, my best friend lives in Utah so some extended range shooting is probably in the future.
It's other purpose would be culling bothersome whitetails on our farm.
At this point the 338 is out because of the comfort level of bench target shooting so I'm trying to decide which 1/2mm increment really tickles my fancy.
Is there any outstanding advantage in accuracy or efficiency between the two? Any suggestions would be appreciated.

THere's a very good bullet selection in 6.5mm.

6,5-06 and 280 both good cartridges. I've heard there's not much gain from "improving" the '06 case, so you may consider the standard 280 rather.
Are there any other considerations? You plan to hunt with this rifle, or is it just for making holes? For long range, I think I'd go with the 280. Some of those bullets' BC's are in the high .500's!

MLC, I built a heavy-barrelled 6.5x55 on a '17 action for F-Class shooting, and it is turning out to be a dandy. Handloaded with a 140-grain AMAX or 142-grain Sierra, I don't think I'd have any problem out to 1000 yards with that cartridge. I've heard that the 6.5x55 Improved gives up next to nothing to the 6.5-.284, today's 1000-yard darling.

Remember that the standard target cartridge in Scandinavia for more than 100 years has been the 6.5x55, and being a factory cartridge does have a certain convenience factor. So you might want to consider the little Swede, too, among your options.

P-17, I must admit the 6.5 x55 has always interested me. I've been eyeing old Sewdes but have been told that you cannot run them to the full potential of the cartridge because of soft steel.
To indulge in a tangent would a 6.5x55 easily feed in a rifle chambered for 6mm Rem, assuming it was rebarreled? 6mm Rem is 6x57 right?

If you're talking about the Swedish 94 or 96 mauser, yeah you'll be limited to the strength of the actions. I doubt they could handle the level of reloading required for long distance shooting. Having said that, my 6.5x55 is a Remington 700 Classic, one of the strongest actions available. It'll withstand much higher pressures than the old military jobbies. If I wanted to get into distance shooting I'd have Hart put an improved 6.5x55 stainless steel barrel, and dig right in. While 6.5 is a popular number for long distance shooting, look around to see what cases are being used. Possibly 6.5x06 or 6.5x300 would be more to your liking. Best wishes.

Cal - Montreal

I would recommend you also 6,5x55 Swedish, I use it in CZ-550 and I am happy with it. Here in Czech republic we have one kilometer competition and last 3 years the winner was using this caliber as well. It is extremyl accurate caliber. You should try it.

I would go with a 6.5 something for sure. The 260 Rem. will get to a 1000 yards in good shape. The 6.5 Sweede in orginal form or the A.I. version is a great to 1000 or a little beyond, and I have seen the 6.5 X 284 shoot very consistent at 1500 yd. Build it on a short action for single shot feeding, hang a heavy barrrel of 28" to 30" on it and enjoy.

Shoot Safe, Shoot Straight........RiverRat

MLC, I have both cartriges, Hart barrels, trued 700 actions. The 280 AI is easier to find good accurate loads for, it is more forgiving in its nature to tune a load for, the 6.5-06 AI is a great round also, but has a narrower preference for powders. The up side is really soft recoil and a shootability that is really a desirable feature. Both will shoot less than 3/4" 5 shot groups with dependability in a good rifle.