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Question About Length After Fire Forming for 6 Dasher...

walker2713

My Boy Hap....
Gold $$ Contributor
Have you found that it makes any difference in the resulting length of the brass after fire forming whether you use the "false shoulder" method or "jam it into the lands" method?

With Lapua 6br brass, it seems that I've got more formed cases that fall below 1.54" when I used the false shoulder technique, expanding up to .264 and using my Wilson die to neck back down to 6mm.

I'd be interested in your experience and comments.

George
 
Myself, I'm more adamant to achieve consistent "blow lengths" then I am to the actual length. I desire 0.004" maximum spread in blow length. Ones that blow shorter or longer, besides being extremes to the average blow length of the array, I find they can directly be effected to capacity variance as well.

My 2-Cents
Donovan
 
I'm assuming by "blow length" you're talking about the length after fire forming? If not, would you please elaborate. Thanks.
 
Thanks.....I'll re-phrase my original question: do Dasher shooters notice significant differences in blow lengths depending on whether the "false shoulder" or "jam it in the lands" fire forming method is used?

George
 
You will notice differences. And yes, I also get slightly longer blow lengths by jam and shoot method…But no, not too significant to fret over.
 
I strongly believe that the reason longer lengths are attained by jamming is because a 6mm case can not produce enough neck tension to keep the case tight against the bolt face when the firing pin hits the primer. Therefore leading to the case stretching from the head(sometimes leading to case head separation) instead of just blowing forward from the shoulder(which will decrease length slightly,like when using the false shoulder method).

To compare you can look at the distance from the old shoulder line to the new shoulder. If some of these measurements are shorter that means your case stretched. If they are all exactly the same,like you get using a false shoulder, you are not getting any case stretch which is what you want to see.

Best Regards
Scott Parks
 
Have you found that it makes any difference in the resulting length of the brass after fire forming whether you use the "false shoulder" method or "jam it into the lands" method?

With Lapua 6br brass, it seems that I've got more formed cases that fall below 1.54" when I used the false shoulder technique, expanding up to .264 and using my Wilson die to neck back down to 6mm.

I'd be interested in your experience and comments.

George


I just Hydro formed 100 lapua cases with Whidden hydro die which leaves the case with around 4 to 5 thou neck tension (I have a 271 no turn neck),
Then jam 107s .025" to .030" with 31gns of Varget.. My average blow length fell between 1.53" to 1.54", some a little shorter and some a little longer. Base to shoulder measurements were on average within .002" of each other and shoulders come out nice and sharp.

Cheers Rushty

Edit: I haven't tried any other method of forming Dasher brass..
 
Hydro formed, and false shoulder formed cases are shorter YES. And are also the most stable of all the methods that are out there to make dasher cases.

Tom
I would really like to know what give you that conclusion that is very interesting thanks.
 
My jam a shoot with 30gr varget
My last 100 all blew out to 1.540 -/+ .002

Also my last set of 100 hydroformed ended up at 1.540
 
Hi George,

For me it's all about results. I've had good seasons, really good seasons, and some poor seasons. I'm very demanding and honest with myself. I know if the conditions should have allowed a better result. With all that said, I've tried jam and shoot, false shoulder and pistol powder(with and without filler), tighter neck chambers using the "step", false shoulder and bullets, and lastly hydro form. The length measurements are what they are, as I said earlier. The results on target have been the best with the later and worse with the former, in the order I listed. These are my conclusions from my results in my benchrest rifles, and nothing more. I might just happen to get great barrels every time I make short brass;)

Tom
that very well might be the conclusion you had really good barrels I cant feel false shoulder or hydroform makes the brass any better your success speaks for itself
 
It could be that with Hydroforming and false shoulder methods that headspace is holding better and the cases are formed closer to 100%. If they are more formed, one would think they would be slightly shorter in length. Matt
 
It could be that with Hydroforming and false shoulder methods that headspace is holding better and the cases are formed closer to 100%. If they are more formed, one would think they would be slightly shorter in length. Matt
I don't buy that for one minute sorry.
 
I don't buy that for one minute sorry.
If a case gets formed harder in body and shoulder without stretching it has to get shorter. When they are formed and not hit hard enough and have slightly rounded shoulders they are longer. I formed and measured thousands of them. When formed with a bullet the bullets slip some and get pushed into the rifling with the firing pin driven forward. Now the body stretches. Matt
 
If a case gets formed harder in body and shoulder without stretching it has to get shorter. When they are formed and not hit hard enough and have slightly rounded shoulders they are longer. I formed and measured thousands of them. When formed with a bullet the bullets slip some and get pushed into the rifling with the firing pin driven forward. Now the body stretches. Matt

Let me rephrase the question I asked are you an Tom saying the brass is better with false shoulder or hydroformed than the traditional seat long with a soft primer method.
 
Last edited:
Tom I think the hydro formed brass just forms better without stretching the body. So it makes more consistent cases. My buddy won both light gun aggregates and set records using hydro brass. If the body stretches or stretches harder on one then another, it let's more or less brass up front to form the case. Now the capacities would change. Matt
 
Yes, I think that's what we're seeing. If we look at what it is we're trying to do, the case head (structure) is the one thing we don't want changed. Virgin br brass has very good extreme spreads of its length. I demand the spread of length to be at least equal to that which it started. Regardless of what the length is in the end.

Tom
Well I guess what you an duckhunt are saying that100 cases I fire formed the traditionally seat long an shoot wont be competitive an live very long
 
Well I guess what you an duckhunt are saying that100 cases I fire formed the traditionally seat long an shoot wont be competitive an live very long
No we are not saying that. I like Tom, have done it all 3 ways. I have won with brass done all ways. They also lasted long. I just think Hydro is maybe a bit more uniform. Matt
 
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No we are not saying that. I like Tom, have done it all 3 ways. I have won with brass done all ways. They also lasted long. I just think Hydro is maybe a bit more uniform. Matt
In order to hydroform you either have to buy the equipment to do that or pay someone to do it.
 

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