Swapping barrels after getting tooled up is no problem at all especially if you stick with the same bolt head. If your worried about head spacing get go and no go gauges to eliminate the guess work. Most of the axis builds I've done the threads are a little tight with all of the hidden blast media in the threads. After the 4th swap its usually all gone and everything is smooth. That being said after I have a proven shooter it almost always stays assembled until I get bored with it. As far as the 22-250 to 270 swap you would need an axis long action trigger guard and mag or single feed it. Check classifieds there are usually axis parts listed.