A gunsmith in Dalton Ga is Ackley Improving the 257 Weatherby, necking it up to 6.5, and shooting the 120g bullets between 3650 and
700 fps.
Not slamming that gunsmith or anyone else who develops their own cartridge, hats off to them. I just wonder what you gain by that particular conversion? The 264 WM has a longer rim to shoulder length than the 257 Roy. What powder capacity advantage (if any) would you gain with an AI'd necked up 257 Roy?
I'm also glad to see the tone of this thread improve. I think mathman hit it. Guys may be running over SAAMI but they aren't claiming not to. Merely that is the load they run.
Sambo, I can't answer your question. For some reason, the gunsmith developed the 6.5/257 Weatherby AI after working with the 257 Weatherby with zero freebore or close to zero free bore. The 6.5/257 Weatherby AI also had minimal freebore. I met 4 guys that owned rifles in this caliber, and they were all grins. One of the guys was coming back from the range after a load development session and he had some very small groups that he had shot.
None of this stuff is new, just very few folks that wild cat will ever come on a board like this and talk about it for reasons very evident in this post. I did not make up this stuff, I learned from different gunsmiths that have built hundreds of these kinds of rifles.
Load development for these wild cats do not differ from any other cartridge, watch for pressure signs, back off when you see them. Scuffed case heads, ejector marks on case head, thinning lettering on the back of the case head, flattened primers, cratered primers(maybe), hard extraction, loose primer pockets are all signs of high pressure. If you only have to neck size a case after firing is what I look for, have not blown up a gun yet in 30+ years of shooting wild cats.
Pac Nor has a great reamer for a 257 Weatherby with zero freebore, or send them 3 dummy cases with the bullet seated at the depth you want, and they will throat the chamber for that seating depth at no extra charge. I sight in my 257 Weatherby at 1/2" high at 200, and I am dead on at 300 shooting the 100's at 3850. My rifle shoots 1/2" groups at 200 yards with the 6-24 Pentax. Crows do not have a prayer with this rifle.
