The main reason is that it becomes part of the size-and-decap process, meaning cases now get trimmed without an extra step.
Giraud Chamfers & Deburrs, the Dillon Doesn’t
I think the Giraud is the more precise tool. It also chamfers and deburrs both the inner and outer edges of the case mouth.
Some claim that the Dillon trimmer does not chamfer and deburr. In actuality, the Dillon’ cutting blade is mounted at a slight angle (I’ve heard 4 degrees) so that the outer edge has a bevel – which means no burrs on the outer edge. I’ve examined several cases under an 8X loupe and so no burrs in the inner edge either. While the edges may not be as nice as the ones the Giraud produces, the Dillon is good enough.
In the attached photo, I have the Hornady Lock-N-Load-AP set up for case processing as follows:
- Station 1: RCBS Lube Die (also de-primes the case)
- Station 3: Dillon RT 1200 Trimmer
- Station 5: RCBS Sizer Die (See Below)
I have the body of the sizer die backed way out so that it never comes in contact with the case. The reason it’s there is so that the expander ball can do it’s job. I also figure that if there are any burrs on the inner edge of the case mouth then the expander ball will knock them off.
The video below tells the whole story: