6 Dasher - Neck "belling" out...*update* 6 Hydro Form Die Results

[bsumoba]

So, I took one of my pieces of brass and put it through a 6 Dasher hydro forming die. Case blew out as expected. I then ran it into my bushing die. The end result was below. The "belling" went away and the turned part of my neck is just below the neck/shoulder junction.

Looks like I might get lucky where I turned it down to. I am hoping that this will be similar to my actual formed barrel in my chamber so I don't have to do anymore turning and I turned all the way down to the neck/shoulder to get a consistent neck.

OAL of the brass was 1.5315". That seems a little on the short side...
Web Area: .4695
Just below the body/shoulder junction: 0.4575
Neck Diameter: 0.4675
Approximate length to neck/shoulder junction: 1.304"
Approximate length to body/shoulder junction: 1.190"

Based on these numbers relative to my reamer print, I am pretty close. Short a few thousandths on most dimensions. I am actually quite surprised how well it blew out.

 

[dkhunt14]

Re: False Shoulder 6 Dasher - Neck "belling" out?

Lapua didn't help when they went from gold box to blue box and reducing the necks and case wall thickness down.

As you can see, the inside fold creases on this brass, it just another weak point. The new and old brass will always burst in the crease fold when forming out.

See the creases in this picture. All new brass has an inside crease folds when it is folded in to make the shoulder.

Wow, I wonder how much brass was removed on those turns. Good cautionary though.

I supplied the brass in the pics to DJ. It is blue box lapua and HAS NOT been turned. I have a fire-form barrel chambered with the same reamer as my match barrel and this brass was formed using the false shoulder method. My chamber is a .271 no turn that was designed around the blue box's thinner neck. I necked up with a 6.5 expander mandrel, then ran the brass thru my Redding Comp neck die with a proper bushing to form the false shoulder at the point where my bolt closed with slight efffort. They were loaded with a moderate charge and 70 grain Noslers for fireforming. The formed brass was then annealed and fired once in a match using 32.7 grains of Varget, 105 Hybrid and CCI450. They were annealed again and loaded for another match. It was at the third loading the splits showed up. It was not in every case from the box of brass but obviously they split where the old neck-shoulder junction of the original 6BR brass.
I shot that brass again this past Saturday without any further cases showing the signs of splitting.
Over the years I have formed a lot of Lapua 6BR into 6 Dasher. Until now, I have never had an issue.

I turn my brass like Donovan but I stop a hair short of the shoulder. I have done thousands and never had a problem. In the pictures it looks like they still are not formed all the way. That is the way my brass looks after fireforming. By the time they have 3 firings they are a lot sharper at the shoulder then those in the picture look like. Maybe not annealed enough. Matt

 

[dkhunt14]

Re: False Shoulder 6 Dasher - Neck "belling" out?

I am using a .25 caliber expander but have tried .264 also and still had the problem. I could not figure out the reason for the belling but it bothered me (even though the cases looked fine after they were fired).

I messed around until I solved the problem by switching to a full length Forster die to size the neck back down instead of a bushing die. For what ever reason the bushing die was causing my problem. Your results may vary.

This sounds right. I remember another shooter I compete against telling me to use a FL regular die, not a bushing die.

If you use a bushing die you can't get a false shoulder. The picture you show looks good to me. I have never seen the belling in mine. I think Ridgeway is right and maybe needs annealing before forming. Matt

 

[Rustystud]

I don't want to piss on anybody's parade. I tried hydro forming Lapua 6mmBR to 6mmBRX. I ruined 300 pieces of virgin brass. Yes, that was expensive and hurt.

Brass and aluminum are ductile metals with what is called in the metal world as "memory".

Example: bend a piece of aluminum or brass. Bend it back, and it becomes stretched at the bend and breaks when bent back.

There is a difference between cold forming and hot forming. Fire forming is a process called explode forming, transfers a lot of heat in the process.

Hyro forming does not transfer any heat in the process.

Metals work harden when being formed. Annealing removes that work hardening.

Good luck with your hydro forming. I hope your experience is better than mine.

I suggest you keep a stiff cleaning brush handy or a modified tap on hand to remove rounds with case head separations.

Nat Lambeth

 

[DJSBRS]

Well if you formed 4,00 rounds and lost 300 that is about right. I have Hydro-formed thousands of Dasher, BRX and BRDX and usually lose 7% on Dashers, 4% on BRX and 1% on BRDX with blue box brass.

What is really an eye opener, using gold box brass, I only lose 3% on Dashers and 2% on BRX and usually less than 1% on BRDX.

Cut the split ones with a tubing cutter and I find they all split on the inside in the shoulder fold.

It is quite evident that we are not getting what we pay for in quality from Lapua. Extractor grooves are not consistent and neck/shoulder thickness is not consistent.

Attached is a picture of the folds that showed up on the outside. Seems pathetic for what we now pay for them. Again, they are making it thinner for a reason and quality has gone down accordingly. They were designed to be 6BR standards not stretched to Dasher or BRX without having some shoulder failures.

DJ

DJ's Brass Service

 

[P1ZombieKiller]

some flaws with the Lapua brass are not as obvious. Some you need to take a closer examination. I cull out 2% - 3% of my Lapua 6br brass before even sizing up for 30br brass. When hydro forming dasher brass, it goes up to 6%-7%.

 

[LRPV]

I see the same thing as Wes. I have had up to 8 pieces out of a box blow out on me or have the fold in them and then the next box, same lot number, all 100 will form perfectly. Some of the cases with the line that just looks like someone cut it, go ahead and form just fine and some blow out with the first hit.

The ones that I have had blow out on me have always been on the first hit which is a pretty light hit. I have never had on make it to a second hit.

 

[ridgeway]

I get one or two of these per box...

 

[22DASHER]

I sure haven't experienced that many failures while forming dasher brass... Must be lucky. I have formed over 800 Dasher casings (all recent blue box) using the false shoulder method and a stout load of Varget. Lost 2 cases in the process.

 

[dkhunt14]

When I see the fold mark I pitch them. I usually get one or two per box. They always blow through and it is not good for your chamber when that happens. Matt

 

[JHardy]

Just a thought: If you do not carefully set your expander mandrel depth , you can easily run the top of the case mouth into the base from which the mandrel originates. That will bell case mouth every time as it tops out. I have not reviewed your sequence of case prep in detail, but given my brief review, it is a thought to consider.

Jim Hardy

 

[LRPV]

I'm not real experienced in this stuff. That being said, I get belled case mouths every time I have tried to size any case down a caliber size all at once. For some reason, standard FL dies seem to limit the bell even though they generally oversize what is actually needed. I have a Forster 6BR FL die that is honed to .265 and it doesn't bell the mouths when sizing back down after using a .257 expander.

 

[dbramley]

I have gotten belled mouths on 7mm cases when I ran an expander mandrel in neck with no lube. I was just opening mouth up another thou prior to seating bullet, put some imperial sizing die and did not get the bell.

Just my experience.