Trimmers using OAL vs. Datum point on shoulder

[Fatelvis]

I have a Giraud and love it. My question is:
Does a trimmer that trims using the shoulder of the case as a "stop" ultimately make less accurate ammo than a trimmer that trims using case OAL? (RCBS, Redding, Wilson, Sinclair, etc.). It seems there is a bit of disagreement about this in other threads. Thanks-

 

[TonyAngel]

Man, I'm jealous. I was going to get a Giraud, but went with a Possum Hollow chucked in a lathe. It's fast, but still leaves me needing to chamfer, although it cuts cleanly enough that I don't have to deburr. Before I got the Possum Hollow, I tried the Hornady trimmer, that works on OAL and the trim lengths were very consistent, but it was slow, even with the power attachment. I then tried the Lee trimmer which spaces off of the "floor" of the case. This was very inconsistent, unless I sort by headstamp and weight and I was still getting more inconsistency than I was comfortable with. I threw that away.

From what I've seen, the trimmers that space off of the case shoulder should be/are consistent with cases that were all sized in the same setup, machine/dies. If they are all sized on the same machine/die setup, the cases should all be the same in terms of external dimensions, so spacing off of the shoulder under those conditions is essentially OAL spacing.

Some guys will trim before resizing and then count on the resizing/stretching to bring the OAL of the case up to a certain range. In this case, I can see getting inconsistencies using a trimming method that spaces off of the shoulder. I think.

 

[fguffey]

As I have said the Wilson case gage measures a case from the shoulder back to the head of the case and from the shoulder to the mouth of the case, reloaders measure a case for length and then use a 'trim to' length, when it is not possible to keep up[ with two0 things at once that is a safe technique;. For reloaders that can keep up with two measurements at one time the Dillon 1200 is a good product, the trim die is also a sizer die, this allows the reloader to adjust the die for sizing the length of the case from the shoulder back to the head of the case AND trim the case length from the shoulder forward to the mouth of the case.

Keeping up with two measurements at once, again I have a 30/06 rifle with .016 thousands head space, not a problem, I adjust the die to add .014 to the length of the case from the head of the case to the shoulder THEN add .014 to the length of the case, instead of a case that is 2.496 long I have a case that is 2.510 long when laying down or 2.510 tall when standing up, and there is a way to form a case that measures chamber length, that would be from the bolt face to beginning of the throat.

The Grasey and Giraud trim cases from the shoulder to the mouth of the case, reloaders should know the head space of the chamber they are reloading for, most do not so they fire first then determine the effect the chamber had on the case, I determine head space first then size the case to off set the effect the chamber will have on it.

http://www.alibaba.com/product-free/255543052/Giraud_Power_Trimmer.html

http://www.matchprep.com/trimmer.htm

For the additional expense of the adapters for each case to be trimmed I prefer the trim/form die, I can adjust the length of the case from the head of the case to the shoulder and the trim die controls the length of the neck from the shoulder of the die to the mouth of the case and the trim/form die is accurate.

F. Guffey

 

[alfack]

I don't know if there is a definite answer to your question, but I have both and get more consistant case overall length with the Giraud. The Wilson has the squeeze fit case holder and I think it introduces an opportunity for variance. I.e. maybe you tapped it harder on one case than the other.

 

[Walkalong]

If you are shooting a match rifle that can tell the difference, worry about it. If not, trim them either way. I know I do.

Plus the Wilson trimmer, which is the absolute best way to get the O.A.L. of the cases all as consistent as possible. I only used it for 6PPC. It sits idle right now.

 

[dmazur]

I am very happy with the Giraud, using it for any cases that gauge "long" with a Wilson type case gauge after resizing.

Many reloaders use a Wilson gauge "upside down" to check trim length. The instructions say to rest it on a flat surface, case mouth up, to use the "trim to" steps on the other end.

The worst that happens is you trim up to 0.006" shorter than necessary, if your cases are all resized to gauge minimum. However, as long as you are consistent in your method, I can't see a problem.

My understanding is that a few thousandths don't make much of a difference in neck tension, and that the goal is to keep the case away from the rifling to avoid dangerous overpressures.

 

[Slamfire]

Does a trimmer that trims using the shoulder of the case as a "stop" ultimately make less accurate ammo than a trimmer that trims using case OAL? (RCBS, Redding, Wilson, Sinclair, etc.). It seems there is a bit of disagreement about this in other threads. Thanks

I use a Giraud and a Gracey.

Since the shoulder, not the base, is the thing that stops a rimless case from going forward, you would think that is the most "accurate" way to measure trim length, bullet OAL, etc.

However millions of shooters have been doing it wrong and swear their technique produces more accurate ammo.

Thus proving that the “placebo effect” is equally effective in reloading as it is in medicine.

I think doing the "Raindance" around the bench works just as well, and the dancing and chanting unnerves all the other shooters, making them shoot poorly.