Although the Bar-Sto is probably the best of the after market barrels (I have several) for Glocks, their "simi drop-in" barrels often DON'T! That's not a knock on Bar-Sto as they admit this up front in their literature. I hear so many people insist on an aftermarket barrel that "drops in" yet gives "match accuracy" that it makes me wonder. Those same people will pitch a fit when their semi drop-in doesn't fit, or function as well as the factory.
By the way, Bar-Sto will fit the semi drop-in for free, you just pay shipping. Two of my Glocks have been 100% reliable since having them "fit" the barrels. If you want the ultimate in accuracy get their fitted barrel, which not surprisingly needs to be fitted.