I am getting ready to do a barrel swap on my Savage 12 and am going with a 257 Bob. This gun will primarily be a deer/medium game gun with an occasional yote thrown in. The bullets I plan on testing when I get the gun together are Barnes TTSX and TSX both 100 grain and Nosler Partition 115 grain. I know standard twist for 25's is 1:10 but was wondering if a 1:9 or even 1:8 would be better choice for these longer bullets at Bob's velocities or if I am thinking into it too much? Thanks,10gauge.

If given the option I'd opt for 1-9"

Never had a problem with 10" twist, but I agree with Steely, if you have a choice

Yep, the last .257 I had built I asked Douglas to screw a 1-9" twist on mine.

I have not shot it a lot yet, but I'm happy with it.

9", end of discussion.

Do not shoot the 80gr TTSX in it... You will never have any reason to look at any other bullet and it will reduce your ability to speculate on things left meaningless...

I have shot a tremendous number of critters with the Roberts from caribou to black bears, Sitka blacktails to whitetails, coyotes to Dall sheep, with a number of other critters tossed in and always looked for a better bullet. When I finally found the right bullets the Roberts had been set aside, and then gifted to kid just starting. The 25-06s I have used since deciding the Roberts was "inadequate" have proven it was far more the bullet than the cartridge.

The 80gr TTSX should shine in a 1:10, but I would opt the 1:9 regardless.

Looking at doing a 25-284 next to shoot just the 80gr TTSX and will be using a Lilja 1:10 because I have it...

Measure the length of your chosen bullet, or see if the manufacturer list it on their web site (Berger does, Barnes does, they also give the minimum twist rate. Barnes 115 grain TSX recommendation is 1:9") then plug in the data here: http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

My Schneider 1:10" twist .257 barrel on a .257 Ackley shoots the Barnes 80 grain TTSX below .5" for 10 shots @ 100 yards. And it shoots Hornady 117 grain factory ammo under 1". But it was built before the lead bullet ban, if I were building one today I'd go 1:9".

Seems like the 9 gets the popular vote. I may try other bullets but these 3 are my short list so far.

9 it is. I've done it on a .25/06 and a .250AI. Great with the longer bullets, equally great with the 75-100gr bullets, too.

Looking like the 1:9 gets more votes than I figured. Just made more sense to me for the longer mono bullets of lighter weight and the longer heavy lead cores too. I always figured better a little fast twist than too slow. I may order 2 barrels the same because I am also interested in building a 250 Sav. AI on my short Remington. Thanks for the responses.