Twist rate for .257 115 to 130 monos; 257 AI

TexasLife · Apr 12, 2026

i went with a 7t for the 26" creed. built for 128-135's. velocities probably won't get over 3,100? lots of bearing surface compared to the 26cals of same weights within the same brand and type (match, hunting, etc). 7.5 wasn't an option or i'd gone that direction

MT Pockets · Thursday at 11:18 AM

Blkram said:
I see that Sierra has announced a 131 gr Tipped Game King (TGK) that will be out this year. They have not yet listed its BC, but its SD will be 0.291. That will provide great penetration on larger big game such as our northern whitetails and mulies, and caribou with a quarter bore!
Checked with the gunsmith and he believes that the new Sierra will perform just fine with the 1:7.5 twist barrel I ordered, which arrived last week! (Was supposed to arrive in June; nice when something comes in sooner than expected!)
(They are pretty busy right now, and do not have space in their shop for my rifle at the moment, so it will go in in June after I get back from Africa, as originally planned, and he'll have some room as he wraps up some other projects for other clients between now and then.)

In another thread, which I haven't found again yet to respond, someone asked if my 24" Benchmark 5R barrel on my 6.5 CM was button or cut rifled, and if I knew what the 24" 25 CM would be.
Upon asking my gunsmith, he stated that Benchmark only brought out the cut rifled barrels a few years back, so the 6.5 CM would have been button rifled when done, and producing the great accuracy (at least to my standards) that inspired the query.
He wasn't sure if the 25 CM barrel is buttoned or rifled, and would have to check the barrel stamp (but believes that it may be rifled).
If rifled, will be an interesting comparison in performance between the two!

I am looking forward to experimenting with the 25 CM!
As stated previously, I have dies, Nosler brass, Hdy 128 gr ELD-X bullets to use with F210M primers and various powders to try (VN555, H4350, Re-16, StaBall 6.5, HD and Match, and Superformance) to experiment with, that should produce velocities in the 2800-2900 fps range. (And then repeat again once I have some of the new 131 gr TGKs!)
And I finally found some of the new Hdy 128 gr ELD-X ammunition for break in, and sighting in the VX-5HD 3-15x44 B&C scope, once the LH Browning X Bolt All Weather is rebarreled.

MT Pockets · Thursday at 11:21 AM

Wow! I have ordered a 7.5 twist .257AI as well and it is due in June as well. What barrel maker did you choose? Mone was Shaw and I can only hope it would arrive early.