You can't accurately machine test these polymer guns, they just don't lend themselves to it (as the thread explains in detail) that is why we have to rely on our skill at fitting parts and our ability to shoot groups. Our customers by in large understand this is what we do day in and day out and fit hundred of barrels every year. We have had only a handful that want a guarantee, and none that want to pay for the added cost of before and after testing, as that is the only way to know the exact percentage of improvement.