Doublehelix3216
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Giraud Tri-Way Trimmer on a motor = heavenly bliss!!!
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Case trimmer
- Thread starter RileyMartin
- Start date
First, there is class of trimmer that is called off the shoulder (once you resize) - the others due to case variance below the shoulder are much inconsistent.
RC20, 'off the shoulder?'. This is what happens when the instructions becomes destructions. Reloaders started calling the Wilson Case Gage a drop-in-gage. Not me; I have always thought of the Wilson case gage as a precision gage. The Wilson case gage has a datum, the Wilson case gage measures the length of the case from the datum to the end of the neck and from the datum to the case head. By the time the reloader starts trimming he should know the length of the chamber from the datum to the case head. Reloaders that do not understand the Wilson case gage are trimming with no clue as to what they are doing if they are setting up on the shoulder of the case.
For the thirtieth time: I have a chamber that is .016" longer than a minimum length/full length sized case/ or / .011" longer than a go-gage length chamber. When trimming cases for that chamber I add .014" to the length of the case from the datum to the case head, when trimming I add .014" to the trim length of the case. Other reloaders trim the .014" from the neck when setting up on the shoulder of the case.
F. Guffey
You wouldn't have to make that 0.014" allowance using one of these "off the shoulder" trimmer types. (I call them shoulder registration trimmers, but potatoes po-tot-oh's). They don't even take the total case length into consideration. With trimmers like these, the case is inserted into a recess that matches the end portion of a chamber so the shoulder stops against this faux chamber's shoulder, same as rimless bottleneck cases do in an actual chamber. The cutter is adjustable to a desired fixed distances beyond the datum line in the faux chamber so that it cuts the case neck a fixed length forward of its shoulder. The back end of the case is just wherever you decide to set your sizing die to leave it. It never enters into the setup of this type of trimmer. Just the neck length does.
Of course, then you need to know how to set that neck length where it should be. I know you do, but for others not clear about it, I expect they mostly just check a few total case lengths when they set the trimmer up, not realizing that's only correct if you know the case is sized to match the SAAMI drawing. Few are, exactly. The better approach is to drop a resized case that has grown a little into a case gauge with an interior datum registration and the two ground limit steps at each end and set the trimmer so the neck lands between the two steps on the neck end, but ignoring the steps at the head end. In a long chamber's case, the head would then be sticking out by whatever extra length it needed to have for its chamber when the neck length is trimmed right.
For those searching, trimmers of this type include the Gracey trimmer, which was the first to use shoulder registration AFAIK, the two Giraud trimmers (motorized and drill powered), the WFT, and the Possum Hollow and probably a couple of others have come along by now. Unless you have some chambers with an unusual neck length, that same neck length setup will apply to all your rifles in that same chambering, regardless of the different resizing lengths you may use for them, so it becomes a set-it-and-forget-it adjustment.
Of course, then you need to know how to set that neck length where it should be. I know you do, but for others not clear about it, I expect they mostly just check a few total case lengths when they set the trimmer up, not realizing that's only correct if you know the case is sized to match the SAAMI drawing. Few are, exactly. The better approach is to drop a resized case that has grown a little into a case gauge with an interior datum registration and the two ground limit steps at each end and set the trimmer so the neck lands between the two steps on the neck end, but ignoring the steps at the head end. In a long chamber's case, the head would then be sticking out by whatever extra length it needed to have for its chamber when the neck length is trimmed right.
For those searching, trimmers of this type include the Gracey trimmer, which was the first to use shoulder registration AFAIK, the two Giraud trimmers (motorized and drill powered), the WFT, and the Possum Hollow and probably a couple of others have come along by now. Unless you have some chambers with an unusual neck length, that same neck length setup will apply to all your rifles in that same chambering, regardless of the different resizing lengths you may use for them, so it becomes a set-it-and-forget-it adjustment.