Hello, I have a pre-'64 220 Swift model 70 hunter grade with a 26" barrel. Does anyone know for sure what twist the barrel has? The throat seems to be extremely long (eroded?) and the only bullet I have tried that will produce a .030" jump to the lands is the Nosler 69gr custom competition. I was wondering if the 220 would be able to stabilize this bullet. Probably going to load @ about 3100 fps. Thanks for the info.