Trimming - measuring off the base or shoulder?
- Thread starter thefitter
- Start date
CatShooter
Since the shoulder can (and does) change position from shot to shot, I measure from the base to the mouth, since the clearance of the chambered round fits in the chamber from base to mouth - the shoulder will find it's place on it's own (hopefully 
)
)CatShooter
thefitter said:
Please understand that even though you FL size all of your cases, it does NOT mean that the distance from a given point on the shoulder to the mouth is the same. Variations in hardness (ergo, "spring back") will effect the measurement - the distance from the head to the mouth is the "real and only" distance that is important.
I use both the Giraud and the Wilson. Absolutely no practical difference in quality between the trimmed cases off either unit. Yes, the Giraud spaces off the shoulder, and yes, the Wilson spaces off the head. It's trimming, not neck turning. A few thousandths difference doesn't matter in this measurment, so long as you've got adequate clearance between the end of the case and the chamber/throat step so you're not "crimping" a chambered round with that step.
Erik Cortina
Team Lapua Brux Borden Captain
I use the Giraud. I anneal, then FL size, then trim. Base to mouth measurement are identical from case to case, so no difference if you do it right.
I use a Sinclair tool that trims off the neck on my HP brass fired in one of several AR-15's. It works quickly as I chuck it in an electric drill. There is simply too much volume for me to trim off the base in 223 Rem. For my HBR rifle and long range rifle I use a Redding lathe type tool and for my hunting rifles I use a Lee trimmer and chuck the cases into my drill. All give my satisfactory results for the intedded use of the case.
Erik Cortina
Team Lapua Brux Borden Captain
thefitter said:
I just told you! Anneal the brass before you FL size, that will insure that the springback is the same therefore sizing all the cases the same way. You then trim the cases and they will all be the same because all the cases are the same.
Erik Cortina
Team Lapua Brux Borden Captain
Yes, I anneal every time.
On new cases I measure a few cases base to shoulder and set my die to the shortest one, then FL size the brass and then trim.
On new cases I measure a few cases base to shoulder and set my die to the shortest one, then FL size the brass and then trim.
I guess I could understand taking trimming to shoulders with NEW brass, since it has not actually been set in headspace yet. But on follow-up trimming I would go casehead to mouths.
My cartridges shorten with fireforming, -from shoulder to mouths, as the shoulders snapping outward pull the necks back.
As it stands, I trim as little as possible(or none) until the brass is fireformed and bumped to correct HS. Then I trim casehead to mouths.
My cartridges shorten with fireforming, -from shoulder to mouths, as the shoulders snapping outward pull the necks back.
As it stands, I trim as little as possible(or none) until the brass is fireformed and bumped to correct HS. Then I trim casehead to mouths.
Erik Cortina
Team Lapua Brux Borden Captain
It really doesn't matter which way you measure, as long as it's consistent.
I know base to mouth is the best way, but if base to shoulder is the same, then base to mouth is the same.
I know base to mouth is the best way, but if base to shoulder is the same, then base to mouth is the same.
I don't believe that Erik.
There are basis for trim length, and it's not just any ole amount shorter than the chamber.
I try to get my trim length within 10thou of chamber end, so that the necks seal soon as possible, to reduce ES.
When you have a bunch of neck & shoulder sooting, you have higher ES. This can be because your load is very slow and/or your brass is hard and/or neck clearance is excessive and/or trim length is excessive.
Also, base to shoulder is seperate and differing from shoulder to mouths. Shoulder to mouth does change, just as base to shoulder changes.
There are basis for trim length, and it's not just any ole amount shorter than the chamber.
I try to get my trim length within 10thou of chamber end, so that the necks seal soon as possible, to reduce ES.
When you have a bunch of neck & shoulder sooting, you have higher ES. This can be because your load is very slow and/or your brass is hard and/or neck clearance is excessive and/or trim length is excessive.
Also, base to shoulder is seperate and differing from shoulder to mouths. Shoulder to mouth does change, just as base to shoulder changes.
I really don't understand people fascination with exact trim length, indexing off the shoulder works just fine for all but serious BR IMHO, I have a Wilson Trimmer, I used it for years, now I use my Giraud Trimmer, since I switched over my shooting has actually gotten better, so the .000000000 whatever differnce between the two has no basis in my world.
Erik Cortina
Team Lapua Brux Borden Captain
mikecr said:
So that's why I can't get my guns to shoot! ;D
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