Fireforming 6 dasher. Consistent shoulder value but inconsistent case lengths.

[_Raining]

After fireforming my shoulder varies about 1 thou over 10 cases measured but the case length varies by about 10 thou over 10 cases measured. I used false shoulder with a 10 thou jam using 30 gr varget and Hornady 105 grain BTHP's. Not sure if it is relevant but I lost 2 out of 100 cases to blown shoulder. The one step I skipped was I did not use a mandrel to re-expand to 6 mm after using the Forster die to size the neck down (expander ball removed). So the neck tension is was pretty high.

It is a no turn neck but I have read that people are getting pretty close tolerances with new lapua brass so that is something I may have to check.

Some of the cases felt a lot easier to go into the chamber than others so that may also be an indication of where the problem is. Is this set of brass trashed? Do I trim to uniform length and sort by case volume? Should I shoot them again and see if the lengths start to get closer together?

I did not size any of the fired cases, they are all as they were after being fired. Should I put them through the sizing die and see if they start to get closer together in length?

I have another 100 virgin br cases from the same lot.

 

[shoot4fun]

I don't think, by virtue of the Dasher's case shape, that the brass is ever going to change much from what it is now.
IME, the best way to get the best brass is to have DJ hydroform it.

 

[Gilbert Garza]

Since you already shot some I would try to size very minimal of the neck to not touch the shoulders or body so it’s not prematurely squeezed. Measure shoulders now but I’m gonna guess it’ll take at least another 2 firings to get fully blown cases.

If you start sizing now you might have a false measurement and wear out the brass faster.

 

[_Raining]

Since you already shot some I would try to size very minimal of the neck to not touch the shoulders or body so it’s not prematurely squeezed. Measure shoulders now but I’m gonna guess it’ll take at least another 2 firings to get fully blown cases.

If you start sizing now you might have a false measurement and wear out the brass faster.

Last night I tried to size the brass, the shoulder grew about 1-2 thou and never shrunk. I guess when it rains it pours. I have a rock chucker and the redding competition shell holders I can try to see if I can get the shoulders to move (I am using a forster press and forster FL die, even cammed over it doesn't touch the shoulder). That brass in my chamber is a difficult bolt close even with the firing pin and ejector removed. Tonight I will give the chamber a good cleaning and see if there is still resistance when closing the bolt and if there is then I will bust out the rock chucker and see if I can bump the shoulders back. I will be a sad sad man if I have to modify the die to be able to bump the shoulder.

 

[shoot4fun]

Last night I tried to size the brass, the shoulder grew about 1-2 thou and never shrunk. I guess when it rains it pours. I have a rock chucker and the redding competition shell holders I can try to see if I can get the shoulders to move (I am using a forster press and forster FL die, even cammed over it doesn't touch the shoulder). That brass in my chamber is a difficult bolt close even with the firing pin and ejector removed. Tonight I will give the chamber a good cleaning and see if there is still resistance when closing the bolt and if there is then I will bust out the rock chucker and see if I can bump the shoulders back. I will be a sad sad man if I have to modify the die to be able to bump the shoulder.

I use Whidden dies for 6 Dasher. I initially had the same issue with not being able to bump the shoulder back so I took an extra shell holder and ground it down ten thousandths. Still having no luck, I finally called Whidden. I returned the FL die with some fired brass and they found my die was left 20 thousandths long during manufacture.
Also, Redding Comp SH are thicker than the standard by the increment stamped on the SH so trying them won't help at all.

 

[_Raining]

Also, Redding Comp SH are thicker than the standard by the increment stamped on the SH so trying them won't help at all.

That is unfortunate. Do you think it would be worth it to try to use the gauges that come with micrometers to prop the case up in the forster shell holder jaw things to try to get the shoulder bumped or should I just give up and send the die off, I was really hoping to start load development this weekend so I am open to any MacGyver ideas to get that case further up in the die.

 

[Delfuego]

Welcome to the wonderful world of Dasher brass! Wait till you get bolt click

I would send you die out to get it shortened asap. I would also run the expander ball or a mandrel during resizing. You could also send your fired brass to Harrell and see if the have a die that will work for you.

 

[Gilbert Garza]

Last night I tried to size the brass, the shoulder grew about 1-2 thou and never shrunk.

This leads me to believe you didn’t use enough lube and the die is pulling the brass

Measure with no primer to the shoulder. Write that down. Then size. If it’s longer, then it obviously grew from case stretch in die.

I also got an old shell holder and removed .015” from the top to ensure my die wasn’t bottoming out.
Unfortunately I had the same issue with a set of Whidden dies for 6SLR, great customer service, horrible quality control, won’t use again.

And the other option after you’ve fired a few times without sizing is send it to Harrell’s. They choose a die that best fits your brass.

 

[_Raining]

This leads me to believe you didn’t use enough lube and the die is pulling the brass

I thought the shoulder increasing was normal for any die. With my 6.5 Creedmoor I would size a piece of brass, then measure it. Turn the die in some more and repeat. The brass would grown by about 1 or 2 thou then eventually the shoulder would make contact and push it down to the desired value. Just in this case there is never that contact from the die on the shoulder. This made sense to me because you are squeezing the body of the case down and that brass has to go somewhere and since the shoulder is not restricted it grows longer slightly. Is this incorrect?

 

[shoot4fun]

I thought the shoulder increasing was normal for any die. With my 6.5 Creedmoor I would size a piece of brass, then measure it. Turn the die in some more and repeat. The brass would grown by about 1 or 2 thou then eventually the shoulder would make contact and push it down to the desired value. Just in this case there is never that contact from the die on the shoulder. This made sense to me because you are squeezing the body of the case down and that brass has to go somewhere and since the shoulder is not restricted it grows longer slightly. Is this incorrect?

You are correct.
The one piece of advice I will give you for the set up of a sizing die is not to run a case in, measure, adjust the die down and run the same piece of brass back thru. Measure a different case each time until you have the die correct. Don't run your sample brass back thru the die until your measurements tell you the die is set properly.

 

[Pav67]

I have a forster coax and had to have them take .010 off there dasher die so I could resize.If your using acoax press make sure the screws holding the plate over the jaws are button head and not cap screw.