6mm Dasher - when to turn necks?

[highpwr]

I am planning to fire form some 6mm Dasher brass for my new barrel that was cut with the Dave Kiff reamer (0.269 neck spec). I will be using the false shoulder method to prepare the Lapua 6BR brass for firing.

After doing some arithmetic it looks like I should turn the useable portion of the necks to 0.012 wall thickness. My question is, do I turn the necks first and then create the false shoulder?
Or, should it be the other way around, create false shoulder and then turn?

I plan to shoot real bullets for fire forming (not COW). May even do some of the fire forming during an actual competition.

Thanks for the help.
Larry

 

[Jay Christopherson]

I'll be interested to see replies to this. I have the same spec as you and my plan was to fireform the brass using the false shoulder/COW method and THEN turn the necks. My reasoning was that trying the turn the necks before fireforming (where the shoulder moves forward, shortening the neck) could cause problems if you're are not 100% accurate when turning down the un-formed necks.

 

[Jay Christopherson]

This might help- this is pretty much what I was planning to do. The author has the same .269 spec and turned the necks AFTER fireforming:

http://bulletin.accurateshooter.com/tag/fire-forming/

 

[tclaunch]

I fireform for a .269"chamber in a BRX and Dasher. What I do is turn my cases as the standard BR all the way down, to help insure no do-nut forms in the fireforming process. This is done first, then false shoulder, then fireform.

 

[highpwr]

I fireform for a .269"chamber in a BRX and Dasher. What I do is turn my cases as the standard BR all the way down, to help insure no do-nut forms in the fireforming process. This is done first, then false shoulder, then fireform.

Sounds like a good idea to me; a little extra space for the brass to flow which helps prevent donuts. I will give this a try. Thanks for the advice.
Larry

 

[johara1]

Larry,
You can not have a false shoulder,you are only turning off app..001 or .002. I don't turn it down to .012 first i turn to .0122-3 then after fired i will turn the finish cut.......jim

 

[highpwr]

Larry,
You can not have a false shoulder,you are only turning off app..001 or .002. I don't turn it down to .012 first i turn to .0122-3 then after fired i will turn the finish cut.......jim

Jim,
I am going to create the false shoulder by necking up to 6.5mm using an exanpansion mandrel then resizing a portion of the neck to 6mm. Maybe I forgot to mention that.
Larry

 

[johara1]

Larry,
OK, but you still have to turn them to have some clearance. I turn about .050 past the point where the neck will end up. How long is your chamber? Mine is 1.569,try to get a blow out length of 1.550- 1.555 if your chamber is that long.They only grow for a couple firings then they just about stop........jim

 

[BigKev]

For what its worth I turned my necks down (.269" reamer) after I fire-formed, however I used the COW method to fire-form and didn't lose a single case or have a single problem doing it. The method I used initially formed the cases about 95% of the way, the second forming with bullets finished off the process. I first created a false shoulder by necking up to 6.5 mm with a K & M expand-iron and then re-sized the neck back down half way with a Redding bushing die. With regards to the "dreaded" donuts K&M makes a tool steel mandrel (option) with cutters on the end of the mandrel that will remove any "donut" material that may have formed during the fire-forming process. Hope that helps.

 

[Jay Christopherson]

If you turn the neck before fireforming, don't you end up with part of the shoulder being "thinner" after the fire-form? Or do you not turn all the way down to the shoulder when turning before fireforming. Or does it just not matter here? Trying to figure if I need to re-think my process... if I can avoid doughnuts being formed, I'm all for that, even if my turner does have a cutter to remove them...

 

[highpwr]

Donovan,
How was the accuracy on target while fire forming?
If I can't get all of the cases formed prior to the F Class match I am thinking of case forming during the match while shooting the 800 and 900 yd stages. Will the 6dasher shoot with accuracy comparable to a 6BR while fire forming?

I'm guessing that standard deviation and velocity spread might not be the best during the forming process but I have not done this before so really don't know.
Larry

 

[alf]

I don't expect steller accuracy until the third firing.

 

[johara1]

A couple other things, don't use wolf SRM primers to fire form they are too hard and get ALL lube off the cases and chamber or they may end up short...........jim

 

[highpwr]

Donovan,
I fireformed 80 cases over the week end and they came out looking just like your picture. I've got to do another 80 next week end and also do some load testing with the fire formed brass.

Larry

 

[Old Navy]

An unturned neck with a bullet seated will not chamber in my .269" neck. Later! Frank