It's fairly simple to check any barrel for rate of twist if you have a tightly fitting brush or patch on a rod with a good swivel end. Just get it started, mark a beginning point Top Dead Center, then move the rod slowly until it makes one exact revolution, mark that point also, then measure the distance between the two marked points. This method is suggested in several old books, and still works well if you have a tightly fitted patch or brush that will let the rod swivel as it is supposed to. I see that you don't have it in hand, but perhaps whoever does could perform the simple test.
