Dasher Headspace Conundrum

[oldduc]

I have been handloading for about 60 years and have a fairly good understanding of what’s going on, but I now have a problem I do not understand. I built a 6 Dasher a couple months ago and have got about 200 rounds through it. It’s been shooting pretty well, but I have noticed that as the barrel heats up, the bolt closes harder and I have been trying to get the headspace figured out a little better. I am using Lapua brass that has been fired and annealed 4 times and I’m using a Forster Bench Rest FL sizing die without the decapper/expander and using a Sinclair mandrel to set the neck size. Anyway, I measured the base to shoulder datum of fired brass at 1.2505. I ran the brass through the sizer, with the shellholder tight against the die base. It still measured 1.2505. I got the same results a number of times and decided to shorten the shellholder from the standard 0.125 height. I took off .002 and resized and remeasured and still got 1.2505. I took off a little more and a little more until I finally got the shellholder down to .115 height, with no change in the case. Out of curiosity, I put some plastigauge on the neck of the cases and closed the bolt and it showed .002 headspace for both the fired and the resized cases.

Basically, I don’t get it. Logically, the case can’t have the same headspace length after I shove it 0.010 further into the die. There must be a simple explanation that I’m not seeing. Any ideas?

Thanks,

~Gary

 

[ridgeway]

Cut some off the bottom of die. Fairly common problem with production Dasher dies....

 

[oldduc]

Cut some off the bottom of die. Fairly common problem with production Dasher dies....

How would it make a difference if i take off the bottom of the die or the top of the shell holder?

 

[jepp2]

I put some plastigauge on the neck of the cases and closed the bolt and it showed .002 headspace for both the fired and the resized cases.

That tells me you need to take more of your shellholder (or die which is much harder). You still don't have the case getting to the shoulder portion of the die yet.

 

[Dusty Stevens]

How many shots between cleaning and how fast are you shooting them?

 

[oldduc]

That tells me you need to take more of your shellholder (or die which is much harder). You still don't have the case getting to the shoulder portion of the die yet.

Yes, the die is about as hard as anything I've tried to work. That's why I did the shellholder. I'll take another whack at it....what's the worst that can happen?

 

[oldduc]

How many shots between cleaning and how fast are you shooting them?

I'm shooting 2 sighters and 20 for record at 600yds in about 18-20 minutes, and cleaning after that. I can still grab the barrel without getting burned, so I don't think I'm over heating it. Most I've shot without cleaning is about 35-40 rounds. I guess I'm a lightweight.

 

[alinwa]

Yes, the die is about as hard as anything I've tried to work. That's why I did the shellholder. I'll take another whack at it....what's the worst that can happen?

Dude, seriously.... if you're not getting enough sizing, SHORTEN THE DIE!

And NOT with a lathe....ya' sidle up to the 8" carborundum benchgrinder with the sizer die held FIRMLY, wrist braced against yer hip just off yer nutsack and you forevermore SPIN the bottom of the die ag'in the grinding wheel. Just smooodge off a pleasant slice and make 'er look good. I've done several where I ran a hunk of allthread thru to make a nice spinney hannle.... I've also cleaned some of them up on the beltsander. Cuz I'm all anal like that. Looks and stuff.

A resizing die should NEVER touch the shellholder so get'cherself some clearance, really.

I have no qualms about doing this for loading a 5000.00 BR rifle.

As you said, "what's the worst that can happen?"

 

[ridgeway]

How would it make a difference if i take off the bottom of the die or the top of the shell holder?

Not sure how much you need to take off. Shellholder is fine, but be aware if you take too much off, the shellholder gets weaker. If you get a tight case, your shellholder needs to be strong enough that it doesn't break. I've had this happen...

Lathe and carbide makes easy material removal. Face inside out to keep burr out of ID.

 

[johara1]

Not sure how much you need to take off. Shellholder is fine, but be aware if you take too much off, the shellholder gets weaker. If you get a tight case, your shellholder needs to be strong enough that it doesn't break. I've had this happen...

Lathe and carbide makes easy material removal. Face inside out to keep burr out of ID.

Then break the inside and outside edges........... jim

 

[PatMiles]

Face inside out to keep burr out of ID.

Excellent point!

 

[savagedasher]

Take a case you have size
Get some blue painters tape
Put one piece on the case head trim it to size put the case in the chamber
The bolt should close with
a little resistance .
It will crush and you will know your headspace from the the thickest of the tape

 

[Had2muchofForums]

A resizing die should NEVER touch the shellholder so get'cherself some clearance, really.

Sir,

Why is that?

Thank You

 

[338rumshooter]

Were you using a different piece of brass each time during your testing?

 

[alinwa]

Sir,

Why is that?

Thank You

Because I size my cases differently depending on several factors and if a case DOES touch the shellholder it kinda' locks you to that one setting. It will work well under one set of conditions and not work at all a day later.

THE ONLY WAY a die can consistently work "OK" when it's touching the shellholder is if it's consistently over-sizing.

Which means your cases will "grow"

Which means you'll have to trim them

Which means you'll be throwing them away soon

Which FOR ME is criminal. I fired cases in a match last weekend which had been used IN COMPETITION in three completely different barrels, 2 rifles. These cases had already won wood when I switched them over to this latest barrel and a brandie-new Kelbly Panda manual eject. I fell completely off the wagon this match, won NOTHING, dropped 5 cases on the concrete (OUCH!!!) from gettin' all a'scited and forevermore JACKING rounds out cuz the action was sticky.....

But enough stupid excuses..... the cases worked for (40-50?? firings) a long time because the shellholder is never a part of the equation.

I'ma' say this once, very quietly, and then pull out and per'tend I was never in...... it's worked before for others, or so I've heard

I sized these cases using Kroil for my sizing lube..... this completely changed my die setting...... but it didn't clean the necks the way I like so I'm back to BBS for a while

The entire concept of "setting the die to contact the shellholder" is flawed on many levels as concerns accuracy but if I were a mfgr of reloading gear, and if I wanted to still be in business 10yrs hence I TOO would write the books the way they do knowing that 99.9% of the people who hack loads together are doing it "to save money."

Please let me be clear here regarding one item of which you may not be aware..... I use ONLY fitted resizing dies. Even on hunting rifles. Every reamer and every die for every chamber I cut/make/order/use for 25yrs has been scrupulously matched.

None of this "minimal sizing for accuracy" applies to factory dies

Nor to factory chambers

The OP "wasn't getting enough sizing effect" and my admonishment to hack the die off was probably somewhat unclear but it's still exactly what I do/have done whenever a die is hitting the shellholder. On ANYthing..... there is no possible gain to it hitting.

Let the opinions begin

 

[Had2muchofForums]

Thanks for the detailed explanation.

 

[Webster]

I have been handloading for about 60 years and have a fairly good understanding of what’s going on, but I now have a problem I do not understand. I built a 6 Dasher a couple months ago and have got about 200 rounds through it. It’s been shooting pretty well, but I have noticed that as the barrel heats up, the bolt closes harder and I have been trying to get the headspace figured out a little better. I am using Lapua brass that has been fired and annealed 4 times and I’m using a Forster Bench Rest FL sizing die without the decapper/expander and using a Sinclair mandrel to set the neck size. Anyway, I measured the base to shoulder datum of fired brass at 1.2505. I ran the brass through the sizer, with the shellholder tight against the die base. It still measured 1.2505. I got the same results a number of times and decided to shorten the shellholder from the standard 0.125 height. I took off .002 and resized and remeasured and still got 1.2505. I took off a little more and a little more until I finally got the shellholder down to .115 height, with no change in the case. Out of curiosity, I put some plastigauge on the neck of the cases and closed the bolt and it showed .002 headspace for both the fired and the resized cases.

Basically, I don’t get it. Logically, the case can’t have the same headspace length after I shove it 0.010 further into the die. There must be a simple explanation that I’m not seeing. Any ideas?

Thanks,

~Gary

Pushing 2-3 thou should make it chamber. Don't understand barrel temp causing tight bolt closure. Temp should cause extremely small amounts of metal expansion. Measure case head expansion above the extraction groove. All reamers are not the same. Send some 3 times fired cases without any sizing, never in a die to Whidden and get a die to fit your cartridge/chamber. Can't remember the details but Kelbly’s told me they specify several dimension besides free bore when they order reamers that should be a standard reamer. They are not all made to the same exact tolerance? You can get reamers with slight dimension variations from the same manufacturer when ordering a specific reamer. A 6BR case fired in my 6BR will not chamber in my 6BRX. A new factory Lapua case chambers easily. A reamer can be run in a little short or long. Was it checked with a headspace guage. A lot of wannabe gunsmiths out there.

 

[KMart]

Because I size my cases differently depending on several factors and if a case DOES touch the shellholder it kinda' locks you to that one setting. It will work well under one set of conditions and not work at all a day later.

THE ONLY WAY a die can consistently work "OK" when it's touching the shellholder is if it's consistently over-sizing.

Which means your cases will "grow"

Which means you'll have to trim them

Which means you'll be throwing them away soon

Which FOR ME is criminal. I fired cases in a match last weekend which had been used IN COMPETITION in three completely different barrels, 2 rifles. These cases had already won wood when I switched them over to this latest barrel and a brandie-new Kelbly Panda manual eject. I fell completely off the wagon this match, won NOTHING, dropped 5 cases on the concrete (OUCH!!!) from gettin' all a'scited and forevermore JACKING rounds out cuz the action was sticky.....

But enough stupid excuses..... the cases worked for (40-50?? firings) a long time because the shellholder is never a part of the equation.

I'ma' say this once, very quietly, and then pull out and per'tend I was never in...... it's worked before for others, or so I've heard

I sized these cases using Kroil for my sizing lube..... this completely changed my die setting...... but it didn't clean the necks the way I like so I'm back to BBS for a while

The entire concept of "setting the die to contact the shellholder" is flawed on many levels as concerns accuracy but if I were a mfgr of reloading gear, and if I wanted to still be in business 10yrs hence I TOO would write the books the way they do knowing that 99.9% of the people who hack loads together are doing it "to save money."

Please let me be clear here regarding one item of which you may not be aware..... I use ONLY fitted resizing dies. Even on hunting rifles. Every reamer and every die for every chamber I cut/make/order/use for 25yrs has been scrupulously matched.

None of this "minimal sizing for accuracy" applies to factory dies

Nor to factory chambers

The OP "wasn't getting enough sizing effect" and my admonishment to hack the die off was probably somewhat unclear but it's still exactly what I do/have done whenever a die is hitting the shellholder. On ANYthing..... there is no possible gain to it hitting.

Let the opinions begin

All of my custom Whidden dies come nowhere close to the shellholder. In fact, when I got the first one, I screwed it down to the shellholder then backed it off about 1/2 turn or so. I sized a case and set the shoulder back about .010.

 

[DJSBRS]

Are you sure it is a FL and not a neck sizing die only?

DJ

 

[oldduc]

Dude, seriously.... if you're not getting enough sizing, SHORTEN THE DIE!"

OK, so I shortened the die about .060. Now I can just about make 6 BRA out of the Dasher brass! I used a disk sander and it worked pretty quickly and smoothly. Put in a new shellholder which doesn't come anywhere near the die when properly set. Might need to take some off the Hornady L&L though. I guess not being a SAMMI spec cartridge means the shops can make the dies however they see fit. Thanks for all the replies.
~Gary