I just got off the phone with a friend who shared with me an experience about a customer who brought him a box of parts. He wanted a 1911 built, and decided it would be a better deal for him to buy the parts and supply them to the builder even though the builder told him not to do buy anything without first talking to him.
When he got his brand new gun back it wouldn’t run properly. Why? Because he had mistakingly bought one part for a 9mm instead of a 45acp. Oops! A very expensive mistake. Now, before you call my friend a big jerk because he didn’t inform the customer, you should know that they are very good friends, and the problem was fixed with a return visit to the shop.
Sometimes you may want a modification or part used that your gunsmith is familiar with and knows won’t cut it in the long run. You should trust him and save yourself the headache of having to make a return visit, or worse having to keep a junky part that no one will warranty.