I have them in 3 gun barrels all thin. All work perfectly. I believe the last ones I had done were well below .040 I will see what I might have written down, I know that it was less then they said they needed as a minimum. On that set the main reason I sent the gun for the tubes was to correct the POI which they did beautifully without having to use concentric choke tubes. Briely gets a thumbs up from me.
Jeff G.