Headspace/sizing problem

[PWC]

40 cal case, used as a comparator, comes real close to the SAMMI 30-06 datum line

 

[Reloadron]

The OP was asking if his Lee die FL resized cases could safely be used. To me this is a question about whether you can trust the out of the box resizing die. He compared a fired case w/ his resized case and found the headspace measurement (case head to 0.375" collar on comparitor for 30-06) difference was 0.018".
One person replied that the resized cases SHOULD NOT be used as the headspace was too short and could result in "Possible case head separations on firing. I had 223 brass separate with .014" shoulder set back." This suggests regardless of your chamber dimensions, resizing a case with a shoulder 0.014~0.018" shorter than your chamber is dangerous, and the cases should not be used for full charge reloads.
Is there a recommended "max undersized" headspace dimension that is considered unsafe? Is the min dimension the listed SAAMI cartridge (min) dimension or can the case be resized even smaller than SAAMI, but how much?

I get that and agree. Going back to the very first post:

My sister bought me a bag of "once fired" 30.06 brass at a yard sale. It looked really good, so I decided to process it. So using my Lee full length sizing die, set as instructed, I resized the brass. (I set the die a little less than 1/4 turn down after the shell holder touched the die.) I figured I would full length size them, shoot them in my gun, then just neck size them afterwards.

Using my comparator, new rounds measure 2.44", and brass fired in my rifle measure 2.48". This used brass measured around 2.49 to 2.50 before I sized it. So imagine my surprise and consternation when I measured the brass after full length resizing to find it 2.30"!! (Yeah, I foolishly sized the whole batch before thinking to measure it while sizing.....)

Now I know what the future cure is; DON'T FOLLOW THE DIRECTIONS! Seriously, in the future I will set the die short, and then measure and set, measure and set, and measure and set until I get the die set somewhere reasonable.

But! What about this brass? Is it ruined? If fired, it will have a headspace of about .018". Too much to be safe? (If I do shoot it, I will anneal it before finishing loading them.) Also, I had read that the Lee full length sizer die was made to do a minimal sizing, so what happened here?

Thanks for any input,
Vettepilot555

Those numbers were way off base as was pointed out so a subsequent post fixed that:

Also remains the question of whether you all think that this brass would be safe to shoot once annealed. Once again, using my case comparator, which measures from shell base to the shoulder datum, new unfired brass measures 2.044". Brass fired in my gun measures 2.048". This brass I just sized with the Lee full length sizing die measures 2.030".

So a NEW round, fired in my gun, grows by .004" in length to fill the headspace. (From 2.044" out to 2.048".) If I fired the brass in question, at 2.030", it would have to grow by .018" to fill the headspace of my gun. Would this be safe? Would it weaken the brass such that further loading might be dangerous?

Maximum Cartridge based on a SAAMI 30-06 Springfield should be 2.0526" -0.0070" so the acceptable minimum for a 30-06 Springfield cartridge base to shoulder datum would be 2.0456". The problem here is I have no idea what the actual numbers would be. But I see where a new round stretches by about 0.004" which is about an acceptable limit. Looking at some Forrester head sapce gauges for the 30-06 Springfield Go = 2.049", NoGo = 2.055 and a Field = 2.058". Anyway back to the Lee sizing die and safety. While I will never say never I have never seen a 30-06 Springfield sizing die of any manufacturer size a case that small. Even if the die is run down as far as it can go I have never seen a die that far off. Will the brass be safe? Well I have seen a 308 fired in a 30-06 chamber. Comes out ugly but fortunately nobody got hurt. Personally I would send the die back to Lee and as to a few hundred pieces of brass if they are in fact that short and that old I would trash them. I just find the numbers a little hard to believe but as I mentioned I will not say never could a die be out by that much. I trash the brass for exactly the reasons you stated and have been mentioned. When the brass is fired I figure something is going to give. I wouldn't tempt fate. So I am in the don't load the stuff corner.

Ron

 

[Slamfire]

One person replied that the resized cases SHOULD NOT be used as the headspace was too short and could result in "Possible case head separations on firing. I had 223 brass separate with .014" shoulder set back." This suggests regardless of your chamber dimensions, resizing a case with a shoulder 0.014~0.018" shorter than your chamber is dangerous, and the cases should not be used for full charge reloads.
Is there a recommended "max undersized" headspace dimension that is considered unsafe? Is the min dimension the listed SAAMI cartridge (min) dimension or can the case be resized even smaller than SAAMI, but how much?

Certainly the case can be sized smaller than SAAMI but you are going to run into ignition issues depending on the action type. Let us say the clearance between case shoulder and chamber shoulder is large and you are using rimless cases. If you have a push feed type of mechanism it is very possible to push the case so far forward in the chamber that the firing pin does not strike the primer. Or, it does strike the primer but does not provide a good energy input, so the primer does not ignite fully, and you get a squib. These are undesirable outcomes. Weapons with claw extractors, depending on how tightly the claw hold the case to the bolt face, will probably fire those same rounds without any issues, but, it depends on the cartridge. I have several 35 Whelen's, one a Mauser action and another a M1903, both claw extractor mechanisms. I have found the slight shoulder of the 35 Whelen does not provide sufficient rigidity for reliable ignition if I have any clearance between case shoulder and chamber. I size these cases to a zero chamber headspace. When I cam the bolt down I can feel at lockup, no forward movement of the bolt (I remove the firing pin mechanism) when the bolt is fully in battery. I also went dumpster diving in my parts bins and found firing pins with greater than normal bolt face protrusion. I also use the most sensitive primers on the market, which are Federal. That fixed my misfires and hangfires in this cartridge.

Incidentally, you can read in Chin's Machine Gun book series how a mismatch between British practice and US Navy practice created a condition where headspace in the Oerlkion weapon system was more or less undefined, and it was huge. But as long as the cases were lubricated, and went bang, this advanced primer ignition, rebated rim cartridge mechanism, was safe to use. Now imagine, it is not locked, there are no locking lugs. Think of how it operates. Breech face to chamber shoulder distance varied as the cartridge ignited. I have not seen a fired case in an Oerlikon but I wonder if the shoulders were blown out to a cylinder.




Not unsafe as long as the case did not separate during extraction. Case lubrication was deliberately applied to keep the case fully on the bolt face during the pressure rise of ignition, and during extraction.