So I see the preferd method currently is trimming a case referenced from the neck vise oal. I believe the main reason is for those that continue on to neck turning and having a consistent length to set the stop on the mandrel while neck turning. What amount of difference are we taking in neck length and variation are we getting one way vise the other?
Case trimming difference?
- Thread starter AJC
- Start date
Struggling to understand how some would trim neck length by itself, separate from all else.
I fully fire form, without body sizing, before neck trimming -whether I had turned necks or not (while cases were new).
Even then I don't trim necks until they actually need it. This is then trimming to COAL.
I fully fire form, without body sizing, before neck trimming -whether I had turned necks or not (while cases were new).
Even then I don't trim necks until they actually need it. This is then trimming to COAL.
That maybe be. But what end do you cut the 2 ft from?
don't think it makes much difference with a rope but with a case I would recommend trimming the end with the big empty hole in it but either way it would still have the same length when measured even if you measured from where you cut
Indexing from the shoulder not the base.
The WFT trimmer trims off the case shoulder, so no matter the cases OAL the case mouth is in the same spot in the chamber.
The WFT also helps when turning the neck because the turner stops at the same point at the neck shoulder junction.
And some people here would bitch if they were hung with a new rope.
The WFT also helps when turning the neck because the turner stops at the same point at the neck shoulder junction.
And some people here would bitch if they were hung with a new rope.
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Until you've fire formed, which is taking a case to real form, it matters not whether you reference from shoulder or case head. Neither are consistent and representing of anything true yet.
As far as neck turning, I don't need or use stops and neck length variance means nothing to my results.
As far as neck turning, I don't need or use stops and neck length variance means nothing to my results.
The datum I use for measuring cases to see if they need trimming is not the shoulder. My calipers measure from the case head not the case shoulder when I measure for OAL. A case trimmed from 2.032 to 2.025 will be the same exact 2.025 no matter whether the cutter indexes off the shoulder or the case head. The same .007 of neck will be trimmed off
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As rimless bottleneck case shoulders are hard against the chamber shoulder when fired, the case mouth distance from its shoulder positions the mouth in the chamber neck.
The spread in case headspace transfers to case mouth positioning in the chamber neck.
If the chamber's "neck space" (shoulder's reference to mouth) is .575", the case's "neck space" should be .565" maximum.
The spread in case headspace transfers to case mouth positioning in the chamber neck.
If the chamber's "neck space" (shoulder's reference to mouth) is .575", the case's "neck space" should be .565" maximum.
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This is not what i expected to hear, so each case that you neck turn is unique and is turned to the junction with no stop used? Interesting....
Meaning when the case is trimed from the case shoulder it is in the exact same position in the neck of the chamber. And the only thing that changes is the amount of head clearance between the rear of the case and the bolt face.
Below as Bart B stated above, the shoulder of the chamber stops forward movement of the case mouth. And trimming off the case shoulder makes sure your carbon ring stays in one position.
This way you can make cubic zirconia diamonds from the compressed carbon and pay for a new barrel. 
So once fire formed the prefered method is still indexing of the sholder or no? I get that a case needs to grow and that trimming will be necessary only after a few shots. I thought having the same exact length of case neck was good for turning, and subsequent to that the same position in the chamber every time. So thats why the newest high end trimmers are now indexing off the shoulder vise just oal.Meaning when the case is trimed from the case shoulder it is in the exact same position in the neck of the chamber. And the only thing that changes is the amount of head clearance between the rear of the case and the bolt face.
Below as Bart B stated above, the shoulder of the chamber stops forward movement of the case mouth. And trimming off the case shoulder makes sure your carbon ring stays in one position.
Yes. The shoulders on new cases are not yet taken to any set, so datums on them are inconsistent. New case OAL is not yet formed & stable. These are meaningless until fire formed. There is no meaningful standard with a cartridge until you've first created that cartridge, and It takes your finished chamber(your best die) to do so.
I turn cases ONLY when new, and I've learned neck turning without reliance on case mouth stops.
It's a simple visual,, a deft touch plus or minus rational,, and as good as you'll get through any act of complicating it.
Trimming is also as simple, and if you can(normally) it should not be done until the case is fully formed & stable. With this, it doesn't matter if you take datum from shoulders or the case head. Ether way, from this controlled condition, case OAL is what you're setting.
You make sure your new/1st firing case is not too long by measuring chamber end length, and then trimming if needed to clear it (this would be rare).
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Mine either.
Never seen anybody's results proving to 90+% confidence that a few thousandths spread in case neck lengths degrades accuracy.
Except the case mouth won't always be at the same place in the chamber neck upon firing when there's any spread in case headspace across all cases.
,.........
Does any bullet seating die index off the case shoulder?
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