6.5/284 or 300 wsm

[Mach 1]

By that same logic then, my 8 lb. 338 Norma Mag will cruise right past that at nearly 2,100 ft/lbs at the 800 yard mark with 250 grain Berger.

Now we enter the discussion of diminishing returns as to just how far we push this envelop to make a point. Any of the cartridges suggested will make a fine sheep rifle with the recoil being subjective as to the shooter's ability to handle the rifle/cartridge/bullet combination. Muzzle brakes can be a blessing for some who enjoy less recoil but then a suppressor will work also but add more weight and barrel length.

The combinations between cartridges, bullets and rifle weight are nearly endless with a fairly large sampling which will be excellent choices for a sheep rifle. No one combination should be considered the absolute 'best' as it will vary by the shooter.

The broader the discussion, the better the information the hunter has to choose from. Enjoy the process!

Quoting the ballistics up at 338 Norma magnum is fine And dandy. But the topic only included the 300 Winchester short mag

By that same logic then, my 8 lb. 338 Norma Mag will cruise right past that at nearly 2,100 ft/lbs at the 800 yard mark with 250 grain Berger.

Now we enter the discussion of diminishing returns as to just how far we push this envelop to make a point. Any of the cartridges suggested will make a fine sheep rifle with the recoil being subjective as to the shooter's ability to handle the rifle/cartridge/bullet combination. Muzzle brakes can be a blessing for some who enjoy less recoil but then a suppressor will work also but add more weight and barrel length.

The combinations between cartridges, bullets and rifle weight are nearly endless with a fairly large sampling which will be excellent choices for a sheep rifle. No one combination should be considered the absolute 'best' as it will vary by the shooter.

The broader the discussion, the better the information the hunter has to choose from. Enjoy the process!

I'm sure your 338 Norma magnum will outperform 300 short mag had extended ranges Just as my 50 BMG will have perform your 338 norma magnum But the original post was between a 300 short mag and a 6.5-284 only

 

[Mach 1]

Wow, those must be magic muzzle brakes I'll have to look into. According to the known physics, peak muzzle break efficiency borders on 50% recoil reduction.

http://precisionrifleblog.com/2015/07/13/308-muzzle-brake/

Getting to 5ft/lbs (223) from 30+ft/lbs (300wsm) is quite a feat.

At one time According to know physics, the earth was flat lol

 

[Hand Skills]

Please enlighten we 'flat earthers'. I'm here to learn, let's get factual.

 

[Mach 1]

I must have struck a nerve lol. I didn't mean for you to take it personal. If your going to get factual you would have to know rifle weights load data and break information for specific guns. The fact is, a 300 wsm with a good break doesn't kick any more than a light rifle chambered in 6.5-284 with no break.

 

[dougduey]

I own both calibers. Once I put a brake on my 300 WSM, it became a joy to shoot. It's my elk rifle. Weighs in at 8 lbs with scope, sling, ammo, and a bipod. I don't even notice it on my shoulder when I'm humping up and down the mountains all day. It made short work of a bull elk in NM this last season. Bang flop using a 200 gr ELDX at 2952 fps. I switched to the ELDX bullet this last season, but have taken many elk and deer with a 180 gr Accubond at 3025 fps.
That being said, I love my 6.5-284. It's a perfect antelope/deer/coyote cartridge. It's super accurate and light recoil without a brake. There are guys taking elk and moose with it. Hell, the Swedes have been killing moose for years in Europe with the 6.5x55
If I had to choose one, I'd pick the 300 WSM since you can do everything with it

 

[Weatherby Fan]

Either cartridge you mention will get the job done, if you go 300 wsm you will more than likely want to put a brake on it, it's a snappy cartridge in a lightweight rifle.
I'm having a flyweight (sub 5lb) 6.5-284 being built right now on a Kimber Montana 84M Action/Benchmark Barrel, it will have a brake installed
Good luck on your build, sounds like some nice parts going into it.
WF