Sinclair has their .081 Flash Hole Reamer #07-3081 for the .204 and most others with the exceptions being the few Lapua cases listed on their site as needing the .0625 reamer. This reamer looks to index from the outside bottom of the primer cup and will center and enlarge the flash hole to .081†but without shape (chamfer) on either end.
Sinclair’s flash hole deburr tool #05-1720 with pilot #26-204 that works off the case mouth does fine IF all you want is to deburr previously fired and not resized cases (collar fits) and are not too concerned about a consistent chamfer shape that can only result if cases are always first trimmed to a set length before use of the tool. Their Generation II tool does it “right†but the shaft is too large to fit through a case neck of less than .22 caliber.
K&M has the Model #UM20STD Flash Hole Uniformer, Master Cal .19 & .20 with a silly looking wire nut handle. They also have the much better lookin #UPSTD Flash Hole Uniformer, Professional – Standard 0.080 with a hex drive end and collar to aid centering but I’m guessing that as with the Gen II Sinclair the shaft is too large to pass through the neck of anything less than .22 caliber, thus the existence of UM20STD.
I wish I had held out for the K&M or some other deburr/chamfer tool that indexed off the bottom inside of the case instead of the mouth but the piloted Sinclair tool was already mine before I was enlightened by a search of this forum.
Will someone please confirm that the UM20STD is a must for use of the K&M tool in .204 Ruger, and that the silly lookin but multi-purposeful wire nut is hiding from view the threads that will perfectly fit one of my three existing Redding handles?
![duh :duh:](./images/smilies/duh.gif)