Looks like a retry neck sized . My sizers , 1 ea Lee and Lyman are squeezing the shoulder before they hit the neck . Not the first time I've had a full figured chamber that made huge gains for necking.

I scored a Lyman die set for 284 Win and ran them in there full touch on the shoulder.

Both the 257 & 25-06' went through the 6.5-257 AI with just a kiss from the 25 cal expander. It actually leaves the ID at .255 anyway without an expander.

The thing is that every rifle we shot last Saturday shot almost identical groups. I know for a fact that the 45-70 and 45 Colts were within their nominal operating windows and expected performance. The 358,257&25-06' are capable much smaller groups . So I don't know where that leaves me with the 7×57 . It may be that that's all it's going to do with this bullet or it might just be a matter of dialing in the happy place . It's been suggested that this chamber, and the 06' too, will come around with a little jump , a running start if you will . The .287-154 Hunter is completely different but has a .2 ish jump if I want the lube groove covered . It offered instant gratification but needs 2450 to hit the numbers.