Bought a set of used 6mm TCU Hornady dies recently for a 6TCU short. Cut .175 off the bottom of the sizing die and cleaned it all up(Lots of old goo inside). Tried putting a piece of brass inside it by hand and realized there was a problem. On my Redding dies the diameter at the mouth of the die is around .375(just rough with calipers). On the Hornady dies it's around .365. Feel sorry for the guy that used these for his 6TCU. Glad I only paid $65 for them. Been buying dies for 45 years and this is my first bad set.