Originally Posted by presspics

Frankly, I believe that all of the aftermarket barrel makers start with standard specs from the factory barrels. Their claim to fame may be because they use different or more precise manufacturing methods. The only exception to this rule would be Bar-Sto. They look at the gun and will improve on the factory design with longer lock up time or different rifling rate etc.

Now, for a S&W M&P which will run lead from the factory I doubt that you will see much of an improvement over the factory barrel. The only barrel that is worth it would be the Bar-Sto hand fitted by them.