243AI case comparator

[Mikecr]

If you bump the shoulder .002" and the assembled bolt closes easy on it why disassemble the bolt for the bolt drop test? Whats the advantage?

That may be right,, or wrong.
But we can determine and manage prudent head spacing through careful measure.

I disassemble bolts to clean them now & then. This is a good time to do that.
It doesn't seem difficult to detention striking and unscrew a shroud. And it screws right back together when finished.

 

[Gregg C]

That may be right,, or wrong.
But we can determine and manage prudent head spacing through careful measure.

I disassemble bolts to clean them now & then. This is a good time to do that.
It doesn't seem difficult to detention striking and unscrew a shroud. And it screws right back together when finished.

The Remington clone I own is simple. I hate doing my Savage. It's easy enough, I'll just do it.

 

[Gregg C]

The Competition shellholders are TALLER, not shorter. They won't do anything for a die that doesn't size as is.

Been thinking about this it posted. I used the wrong word, those ARE in fact, taller. But isnt the "taller" portion of,the holder where the case head sits, not,the top of the shell holder? Which would push the case up in the die that much more? Which would move the shoulder down, increasing case to chamber spacing? I don't own any, yet, but, if I needed to move the shoulder away from the bolt face, I'd just screw my die out. Have I got that wrong?

 

[Gregg C]

If you bump the shoulder .002" and the assembled bolt closes easy on it why disassemble the bolt for the bolt drop test? Whats the advantage?

It helps to get all friction ( force ) off the bolt handle. The bolt will actually DROP closed when I get the shoulder moved. Kinda cool, really.

 

[Mikecr]

Been thinking about this it posted. I used the wrong word, those ARE in fact, taller. But isnt the "taller" portion of,the holder where the case head sits, not,the top of the shell holder? Which would push the case up in the die that much more? Which would move the shoulder down, increasing case to chamber spacing? I don't own any, yet, but, if I needed to move the shoulder away from the bolt face, I'd just screw my die out. Have I got that wrong?

You have it backwards. Easy enough to do for sure.
Posted by bigedp51 in another thread here:
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A normal shell holder has a deck height of .125 and the plus .010 competition shell holder has a deck height of .135. Meaning the plus .010 competition shell holder pushes the case .010 less into the die.

All the competition shell holders are designed for "LESS" shoulder bump than a standard shell holder in .002 increments from +.002 to +.010

And if you need more shoulder bump you lap a standard shell holder.

Simply put, using the competition shell holders is like putting a feeler gauge between the shell holder and die for less sizing. Meaning the +.010 shell holder is like placing a .010 feeler gauge on top of the shell holder and then adjusting the die down to contact the feeler gauge.
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[Koda_]

The competition shell holders have the same height and outside dimensions as a normal shell holder its the pocket the cartridge shell sits on thats lower in .002" increments.

You can achieve the same effect by unscrewing/raising your die a tiny bit maybe 1/16" turn I cant recall. Forster makes a good die lock ring with .001" indicator marks on it that works great for this.

 

[Koda_]

It helps to get all friction ( force ) off the bolt handle. The bolt will actually DROP closed when I get the shoulder moved. Kinda cool, really.

it is pretty cool the way it works, but im just wondering what the advantage is over measuring your shoulder datum?

 

[Gregg C]

You have it backwards. Easy enough to do for sure.
Posted by bigedp51 in another thread here:
------------------------------------------------------------------------------------------------------------------------------------------
A normal shell holder has a deck height of .125 and the plus .010 competition shell holder has a deck height of .135. Meaning the plus .010 competition shell holder pushes the case .010 less into the die.

All the competition shell holders are designed for "LESS" shoulder bump than a standard shell holder in .002 increments from +.002 to +.010

And if you need more shoulder bump you lap a standard shell holder.

Simply put, using the competition shell holders is like putting a feeler gauge between the shell holder and die for less sizing. Meaning the +.010 shell holder is like placing a .010 feeler gauge on top of the shell holder and then adjusting the die down to contact the feeler gauge.
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Oh. Well, crap.

 

[mudflap621]

it is pretty cool the way it works, but im just wondering what the advantage is over measuring your shoulder datum?

Where do you measure from without having a good starting point? Most people bump to early and therefore they are bumping too much and don't even know it.

 

[QuietTexan]

it is pretty cool the way it works, but im just wondering what the advantage is over measuring your shoulder datum?

It establishes the max headspace measurement for a particular chamber. The measurement you're taking off the datum has an unknown maximum until you actually have a bolt not drop, then drop.

 

[Koda_]

It establishes the max headspace measurement for a particular chamber. The measurement you're taking off the datum has an unknown maximum until you actually have a bolt not drop, then drop.

So the advantage is its a much more precise way to establish max headspace than just measuring the datum from a fireformed case.
Good to know, thankyou.

 

[Mikecr]

You can achieve the same effect by unscrewing/raising your die a tiny bit

Not really.
This operation centers on camming over with the shell holder deck against the die bottom.
So you set the die to do that, and then change shell holders to sneak into a good shoulder bump.

You do need a well fire formed case for this testing.
One that is resisting bolt turn slightly, which can take ~3 fire formings (without bumping) to get.
That is, an unloaded bolt won't drop freely on this case.

It can get tricky if you're FL sizing, as this moves brass up the case and often moves shoulders forward -before backwards.
So take a good measure of a shoulder datum before any sizing, write the number down. You need to be bumping from there, and not where the shoulder may move to along the way.
Validate final setting with a few fire formed cases before rolling into a big batch.

You lock the die ring, log the shell holder needed. You shouldn't need to do this much anymore.
But ALWAYS measure every shoulder bump, every time.
Every case has it's own character, and takes bumping a little different. Once in a while you run across a case that bumps too much, or not at all. You can tweak bumping within a ~0.5thou range either way with moderate lube on shoulders.

For cases that don't bump initially, and you lube a little more to get a bump,, set them aside and remeasure them in a week.
See if they're behaving. If not, it's time to decide if you want to toss the offenders, or anneal shoulders. You don't want to be fighting this in batch, over & over.
If the shoulder is different, the whole case is different. Chances are it affects the pressure curve and MV.
Where it's MY choice, I toss it, because I had already completed a deep body dip anneal on the whole batch before 1st firing.
They should ALL be the same.
My bumping is 1thou (+/-) 0.5thou

 

[QuietTexan]

So the advantage is its a much more precise way to establish max headspace than just measu4ing the datum from a fireformed case.
Good to know, thankyou.

There's an assumption implicit to calling a case "fioreformed" that' it's actually expanded to the full size of the chamber. Firing once, twice, even three times often isn't enough to fully grow a case.

 

[mudflap621]

So the advantage is its a much more precise way to establish max headspace than just measu4ing the datum from a fireformed case.
Good to know, thankyou.

Your measuring the same either way but without knowing your true headspace in that chamber how do you know how far to set back?

Like stated a lot of people will fire once than automatically start pushing shoulders when in reality most cases I've played with need multiple firings to form to the chamber.