Easiest way to tell the twist is with a tight patch on a cleaning rod. Wrap a piece of tape with the end sticking up like a flag near the handle end of a cleaning rod. Push the rod into the chamber until it makes contact with the rifling, make another mark on the rod and observe the position of your tape flag. Pushing the rod down the barrel watch as the flag as it rotates and stop when your flag makes one complete rotation, mark the cleaning rod again. Once you have two marks on your cleaning rod remove it and measure the distance between the marks, that should let you know how many inches it takes to make one revolution.
I'm guessing it will be a standard twist for the 7mm bullet, which will probably be somewhere in the 1:9 range. There weren't as many options in bullets back in the day when Ackley was making barrels and there wasn't a huge demand for fast or slow twist 7mm barrels.