OzFclass

Hi All,
Went out yesterday and fireformed some brass in my new 6 Dasher and 2 of the 50 didn't fare so well.
One split the shoulder open 1mm approx and the other just cracked the shoulder.
Is this to be expected with a wild cat?
I tried to put up a pic but it wouldn't let me.
Load 32 gn 2208 behind a 105 BER.
Initial fireform loads look promising, 15 shots into 32mm @ 300 yd

Hi Tim
Yes it's not uncommon, it's normally in the middle of the shoulder. I suspect it's a flaw in the brass during manufacture.
Matt

Hi Tim, I agree with Matt. I do take an extra step of annealing the brass before I fire form, most would not. Many use a stiff first load and yours appears ok.

Tim- are you using the false shoulder method? I found this worked the brass a bit and I got split shoulders. In the end I just load a normal BR load in virgin brass- around 30-30.5gr 2208 with 3- thou neck tension and jam a nosler custom competition or any other cheap 105 bullet 20-30 thou and just fireform like that. Once fireformed I will give it a normal load to fireform it a second time at a club shoot then the brass is right to go.

Brad,
Yes I put a false shoulder on the cases with a 25 cal expander.
They came out good, except for the two mentioned.

Brad Y wrote:Tim- are you using the false shoulder method? I found this worked the brass a bit and I got split shoulders. In the end I just load a normal BR load in virgin brass- around 30-30.5gr 2208 with 3- thou neck tension and jam a nosler custom competition or any other cheap 105 bullet 20-30 thou and just fireform like that. Once fireformed I will give it a normal load to fireform it a second time at a club shoot then the brass is right to go.

Brad
The problem with the method you have described, is IME the cases come out all different lengths, some even longer than when they went in, so the case is being moved forward before the powder is being ignited. Using the false shoulder method my cases all come out with-in a couple of thou of each other.
Matt

Split cases:
se

One of the groups shot while fireforming off a clean barrel.
le fire forming at 300 yds

The 15 shot group, hope I'm not boring anyone

How many shots through this barrel now, Tim ? Are you breaking in a new barrel as you do your fire forming ? Or was this A barrel previously chambered as something else ?

Great photos Tim. You would have to be happy with the Dasher?

Matt, perhaps what we are seeing is that the new brass is not all the same in terms of hardness/ tensile strength and so they vary in length when you fire-form. Maybe what you do is limiting the flow of brass - in fact work hardening the brass a tad with the false shoulder which does assist if the brass is too soft. This method is actually doing a service of culling brass which being dissimilar will bite you later anyway.

I anneal, size and work the brass with a Sinclair expander to minimise variable expansion profiles of parent factory brass before I fire them. This saves a few cases and I have time on my hands. I re-dress cases .i.e. anneal, trim, work harden the neck a tad with the Sinclair tool after annealing; and sort with volume after the 4th firing when cases are cherry ripe. At this time I re-visit load development with some cases and I am good to go with others.

In Brad’s case, and it is something I do myself, is put a fair amount of neck pressure on the projectile and jam it into the rifling to make sure the case is centred in the chamber. It seems to be sufficient to resist the firing pin fall which would otherwise push the shell forward. I usually go with a stiff load for the first firing to sort a few wrinkles and don’t worry about the headspace variance.

My view, is that I want the walls of the case expanding evenly, in order to prevent them thinning on one side through brass flow if the case is not centred in the chamber. I also think the neck is more critical than headspace in terms of case memory and future concentricity. The headspace will take a couple of firings to form properly anyway.

Whether your cases are within a couple of thou or more, (maybe in Brad’s case), neither have reached final dimension and need subsequent firings. I do these subsequent firings with a milder load to allow the brass to settle. Then I bump the shoulder back .0005” to .001” so that the headspace does not influence the barrel vibrations by imposing tension on the threads for an accuracy load after the 4th firing. The natural spring back about these dimensions settles.

To further refine procedures, I sort cases by volume at the 4th firing and batch cases accordingly. This seems to sort brass that differs in flow characteristics in the original batch.

Either method will sort itself out with future re-loadings, and case culling.

Hey Tony,
This is a new Dasher from Matt Paroz, after yesterday I now have 54 through it.
Both groups were shot off a clean barrel too.
I had to take a break during the fire forming as the cattle thought that the target was placed on the best grass in 500 ac????
It's nice to be able to shoot groups at 6am when flags aren't needed.

Matt

Yes David is right the key was upping tension and jam to get them consistent. I trim them all to same length after a couple of fire forms. They pretty much don't grow after then. I went from losing cases to not losing cases so a bit more case prep was ok to do in my mind.

just wondering if anyone has tried hydraulically forming dasher cases?




sample cases left to right

std 30-06 case, hydraulically formed 7mm06 40 degree improved case, neck turned 7mm 06 40 degree hydraulically formed case ready to finalise fire forming procedure, complete fire formed 7mm 06 40 degree improved case

note -when hydraulically forming- dies are set so a slight crush or interference is felt when chambering, prior to final forming with slightly reduced powder loads.

cheers
dave

Brad
I have never been able to get enough neck tension to stop the case moving forward when the pin strikes the primer.
Matt P