Everyone seems to suggest 1-9, 1-10 twist for the
257. I had mine done 1-12 on the reccomendation
of some article read 4 or five years ago. It stabalizes the 100 gr nbt completely. I am advised it will also handle the 120's but I use the 6.5 for this bullet weight. Any comments or input would be appreciated.

Jeff

I use a 87 grain flat base bullet most of the time since it is more accurate then a boattail. If shooting past that a 90 hpbt does a great job. Good luck

I shot a .257AI for years. It had a 12" twist, and shot 100gr Nosler Partition very accurately.

Jeff:

I think you are right on the money with the 12" twist for 100 grain bullets. Standard twist is 10" which is closer to ideal with 117 & 120 grain bullets. I would think 14" twist for bullets lighter than 87 grains.

It depends on the barrel, but I would guess you would achieve acceptable groups from your 12" twist with 120 grain bullets.

www.cybermesa.com or greenhill formula