So which caliber, in what rifle ? The 6.5 Creed, the 6.5x55 Swede, or the .257 Roberts

[Mustangs Rule]

Well, no. The 6.5 CM can use the same bullets as the Swede, just at about 50fps less velocity. Results will be the same. Charles Sheldon took an inordinate amount of Alaskan game (with dozens of grizzlies) with the 6.5x54 Mannlicher at velocities lower than the 6.5 Creedmoor can achieve. Ditto the 6.5x55's of that era.

Still, the 6.5x55 is a pretty cool round - I view the Creedmoor as a SA version of it. Chambering the 6.5x55 in a LA certainly does give a lot of seating latitude for long bullets.

all you say is true, and i will add this; the long action not only allows for more powder but also allows for more less seating depth which can be so critical for finding needed for maximum accuracy, especially so for copper bullets, which can have a very narrow range for optimum accuracy.

Years ago i had my only ever custom rifle made. It was filled with flaws. One it being a 35 Whelen, the standard 98 Mauser magazine box was 1/8" too short for the ideal longer COL for Barns bullets and putting what fit in the magazine offered lousy accuracy.

 

[std7mag]

You are confusing the cartridge with the rifle. The ruger77 RSI has a 1-10 twist. The original in the savage 99 had a 1-14 twist.

The original was the Savage 250-3000 in 1:14 twist Savage 99.
The cartridge/rifle originator wanted a 1:10 twist to shoot heavier bullets to be suitable for deer and antelope.
Savage stuck with the 1:14 and the 87gr bullet to get the advertising advantage of having 3,000fps.

Later, after many complaints of bullets failing to penetrate, Savage came out with the 1:10 twist to shoot the 100gr bullets labeling it the 250 Savage.

 

[std7mag]

Probably going on 10 years ago now, I picked up a Ruger 77 MKII in 257 Roberts, used.
The shop was asking $400.
Told the guy to let me think about it.
Went outside to smoke a cigarette and hopped on GunBroker.
Lowest price at that time was $900.
Went back in, looked at the guy and asked if $400 was his lowest offer.
$350 plus tax and transfer.
Love this rifle!!