I have only had experience with two ER Shaw barrels. One was a .257 Roberts owned by a friend and the other is a .243 Win, I own. The Roberts wouldn't do better than 3" at 100 yards before firelapping. It felt like it had two tight spots in it before firelapping.
The .243 Win. is OK for a deer rifle, about 1 1/2" groups at 100 yards, but for the price of a barrel and installation ..... I would buy something else, even at a higher cost, and have less of a chance of getting a bad one.