Resizing issue

[Bart B.]

Guffey's coment:

If the 47 time fired case was being driven to the front of the chamber by the firing pin strike your cases would have stretched between the case head and case body, you measured case length, had you measured the length of the case from the case head to the case shoulder you could have could have determined the effect the chamber had on the case when it was fired.

I did that during the above 47 shot test. Starting out with a 1.628" case headspace in a SAAMI GO gauge chamber, firing it caused the case to have about 1.629" case headspace afterwords as well as the case length shortening a few thousandths. Full length sizing the case and setting the sized case headspace to somewhere between 1.627" and 1.628" ended up with the case length growing about 3 thousandths. At the end of each fire, size, reload and fire again the case grew about 1 thousandths in length.

Note also that the case shoulder set back a thousandth or two from firing pin impact; verified by chambering an empty primed case then firing it.

[F. Guffey]

Bart. B. your claim started with a Sammie sized chamber and full length sizing, 47 times, straight away I wonder why you failed to weight the case first, the proud owner of the new rifle handed me a case, I did not have to wonder how many times the case had been fired, a wild guestimate of the number of firings would have been 35 +/- a few. Again, the case was thin, where did the brass go?

and I ask him if he had but one case, I ask him if he was loading and firing the one case over and and over ect..

Back to the Sammy chamber and full length sizing 47 times, when added to the primer protrusion in the second response (to my comments) as in no bullet, no powder, just a case and primer, if the chamber was Sammie specification and the case was full length sized, why was there no primer protrusion? Are you claiming an exemption”?

F. Guffey

[Bart B.]

Guffey's comments:

your claim started with a Sammie sized chamber and full length sizing, 47 times, straight away I wonder why you failed to weight the case first, the proud owner of the new rifle handed me a case, I did not have to wonder how many times the case had been fired, a wild guestimate of the number of firings would have been 35 +/- a few. Again, the case was thin, where did the brass go?

I had no interest in knowing how much the case weighed. The brass from my case went in the trash can. Where it came from's mentioned in the last paragraph of post 23 in this thread.

Back to the Sammy chamber and full length sizing 47 times, when added to the primer protrusion in the second response (to my comments) as in no bullet, no powder, just a case and primer, if the chamber was Sammie specification and the case was full length sized, why was there no primer protrusion? Are you claiming an exemption”?

No exemption claimed nor expected. It was obvious to me that the force of the primer's explosion inside the primer pocket didn't push back on the primer cup with as much force on the firing pin as the firing pin spring put force on the pin. And the friction needed to move the primer out of its pocket had to be overcome, too, but wasn't. When the pin's force on the primer's less than the primer's force on the firing pin plus overcoming friction between the primer cup and primer pocket will the primer protrude above the case head. There's one other situation when primers end up protruded from the case head with live ammo; I'll not go into that at this time.

I've fired several 7.62 NATO rounds with no powder in them, just primer and bullet, and the 190 grain bullet stayed in place and no primers backed out whatsoever. 'Twould take over 1000 pounds psi in the primer cup and case to push that primer back out against a 26-pound firing pin spring. No, I didn't load that ammo; 'twas issued to me for a match.

[F. Guffey]

“'Twould take over 1000 pounds psi in the primer cup and case to push that primer back out against a 26-pound firing pin spring......”

In your rifles, I do not know, but in my rifles the first thing to appear is the dent, on your rifles, I do not know but on my rifles when my primers are hit with a go-rillo firing pin the size of the dent is reduced when the primer conforms to the firing pin, when the primer fails to fire the dent remains the same after being hit with the go-rillo firing pin. Either way, the firing pin does not move unless the spring is weak, a weak spring can lead to a punched primer caused by the primer turning inside out when it pushed the firing pin back.

When the .7854% rule is applied to your 1,000 PSI in your rifle primer (not my rifle) there seems to be something very strange about your rifle, because? Although I could have a go-rillo firing pin the area of the firing pin does not equal 1 square inch, back to the .7854% rule.

Then there are your primers, unique and different from my primers, my primers, when struck, are not directional, my primers are equal in all directions meaning the primer pushes itself out of the primer pocket or the primer pushes the case forward, then there are crimps and chambers that are equal in length with to the case from the head of the case to its shoulder, you started with a Sammie chamber that is longer than a minimum length/full length sized case, you fired and full length sized the case 47 times.

It is another of those events that make reloading unfair, most would have annealed the case, others would have had case head separation, others would have had to grind the base of the die and or lowered the deck height of the shell holder because the case would have acquired a resistance to sizing, meaning when a case gets that tough it is very difficult to stuff the case back into the full length sizer die.



Quote:
1. As brass is fired multiple times, it flows forward, thickening the neck and shoulder area of the case, lengthening it in the process.

2. As brass flows forward, it also thickens the neck walls, reducing the internal dia. When the round is fired, normally the neck expands to the limits of the chamber, allowing the bullet to pass forward into the throat.

“This ain't what I observed when I loaded and fired the same case 47 times” You did not experience brass flow? You did not experience donuts at the shoulder/neck juncture? Well? you do not have brass flow, I do, I have brass flow, I have nothing to gain by firing a case 47 times, I had rather load 47 cases once, or twice, three times etc., the first failure will be the necks, then if I have a Sammie size chamber and full length sizing to minimum length I am going to experience case head separation long before I reach 47 firings.



I ask about stretch and flow, or is it stretch and or flow, when a case lock onto the chamber brass flow is made difficult on the outside, I have never found a case with skid marks on the outside. I have cases that I fired once, after having been fired once the case had all the use knocked out of it. I was not testing the case, I was testing the rifle.

F. Guffey

[Bart B.]

Guffey, force equals pressure per square inch multiplied by the area it presses against. The inside of a large rifle primer cup at it's bottom is about .0191 square inches (.156" diameter for a Federal 210, squared times .7854). 1360 pounds per square inch multiplied by .0191 square inch equals 26 pounds of force.

I forgot to subtract the .027" cup thickness Federal large rifle primers have so pressure needed's 360 more than 1000 pounds per square inch I first stated. And that pressure presses the sides of the cup against the pocket wall, too.

Note also that the .308 case was driven hard against the chamber shoulder from firing pin impact and there's a thousandth or more case head clearance to the bolt face. The force of the primer's explosion on the pocket's bottom ain't enough to drive the case any more forward. And the .045" diameter flash hole lets some of that energy go into the case body which will reduce the presure in the primer cup by some amount I don't know how to calculate. Verified this by firing several primed cases without powder or bullet measuring their case headspace before and after each time. Average shortening of this measurement was about .0015". And not one single primer backed out of the case; they were all about .002" below flush with the case head.

With a live round, its body stretched back until the case head stopped against the bolt face drawing brass back out of the neck and up the shoulder therefore shortening the case as it expanded against the chamber wall. This is why the case was shorter from head to mouth after it was fired. When the diameters of a fired case are larger than before it was fired, the brass mass remains the same so the case ends up shorter. The reverse happens when the case is full length sized; brass gets moved forward as the case diameters are reduced. Most folks believing firing stretches a case do thinking the case head's held hard agains the bolt face by the extractor and stays there when it's fired. This only happens when bottleneck cases headspacing on their shoulders fit the chamber very tight with zero head and shoulder clearance; the bolt typically binds hard when closed on such a case.

A friend got 56 reloads on his Federal case full length sized in a die a lapped its neck out. His rifle was clamped in his free-recoil machine rest and the 57-shot group on the 100 yard target was about 3/8ths inch center to center between widest shot holes.

[F. Guffey]

“And the .045" diameter flash hole lets some of that energy go into the case body which will reduce the pressure in the primer cup by some amount” And your cases have a one way valve that will not allow 50,000 PSI hot high metal cutting gas from the case to escape back through orifice? flow control hole called the flash hole, not fair, when a primer gets punched hot high pressure metal cutting gas escapes through the punched hole, and you are telling me the high pressure in the case ignores the flash hole when PSI is equal in all direction

Again, it is not fair, they sell you the cases with the tiny, little bity small flash holes, I get the culls, my flash holes are .065”+, one member on this forum purchased 100,000+ cases, he ask me if I had any interest in all or part of them, all the cases were used in load development, outside of reloading the cases I had no interest in them. The flash hole in the cases used to develop load must have been culls, the member is a very disciplined reloaders, he measured the cases for excessive pressure. he measured the flash hole diameters on many of the cases, for the cases he did not sell he drilled the flash hole all to the same diameter, JIC as in ‘just in case’ it mattered, being one of the few I know that measures the diameter of a flash hole and he measures before and again after..., I have offered to allow him to measure the flash holes in some cases I have used to to test rifles.

I do not have an exemption and time is a factor. My primers hit the bolt face, the pressure inside the cup flattens as in removing the dent and or forcing the primer to conform to the protruding firing pin, yours are countersunk .002” FANTASTIC!. Then there are reduced loads.

F. Guffey

[hooligan1]

I don't mean to get in between you fellas, because you guy's forget more info than I can ever use,,,,,, but if my primers are somewhat flat and the firing pin strike is cratered as to actually have a rim around it what does this mean?

[PA-Joe]

You should get a little flattening and a crater around the firing pin. You do not want the flattening going out all the way the the rim of the primer. Some rifles have over cut firing pin holes and that is the main cause of teh crater ring.

[F. Guffey]

Hooligan1, if what Bart B. is saying is true there is not enough pressure in the primer to flatten your primer and or force the primer back and around the firing to create the crater.

“What does this mean?”



Thanks for asking,

F. Guffey

[Bart B.]

Mr. Guffey, my comments on pressure in a primer pocket were made discussing what happens when an empty primed case is fired. Not with a live round. Go back to post 30 and read the third paragraph. But they can back out with live ammo; please read on.....

Some years ago, I loaded 10 rounds of .308 Win. ammo with new cases primed with Fed. 210's, 165-gr. bullets with IMR4064 having decreasing charge weights in each case starting with 44, then 43, 42, 41,40, 39, 38, 37, 36 and 35 grains. I measured case headspace with each one and marked the case with charge weight and case headspace. With the 44 down through 41 grain loads, fired case had .001" or .002" increase in case headspace and its primers were all flush with the case head. When the 40 grain charge one was fired; its primer stuck out .001" And that fired case headspace was .001" shorter than when new. Charges 39 through 35 had successively more primer protrusion. Fired case headspace also got increasingly shorter than when new by about .001" per load. The case with 35 grains ended up with its primer sticking out about .006" All this, to me, indicates the case shoulder gets set back from firing pin impact and pushed out of the case as pressure gets higher. If there's not enough powder in the case to make peak pressure high enough to push the case body back so the case head stops against the bolt face, the primer will end up sticking out of its pocket and the fired case will usually have less headspace than when it was new.

Hooligan1, that ridge sticking up around the primer's dimple is typically caused by one of three problems. . . . .

One is the hole in the bolt face is too big for the firing pin's tip diameter. Had one that way but a 'smith hard chrome plate the firing pin tip making it .010" larger in diameter; no more cratered primers.

Another situation is a insufficient pin protrusion from the bolt face when it's at its stop inside the bolt or cocking piece. Primer cup metal gets pushed up around the shallow dimple cratering it. Firing pins should protrude a bit more than their tip diameter so its rounded tip fully indents the primer crushing the priming compound fully against the anvil inside the primer cup. .055" to .065" is typical with most centerfire rifle firing pins. If this is the cause, a new firing pin is needed that's going to let its tip stick out of the bolt face enough. Some firing pins can have their stop shoulder ground back a bit to solve this problem.

And finally, a weak firing pin spring may well fire the primer but it will get pushed back by normal peak pressure inside the case which also presses against the primer cup pushing the pin back and cratering the cup metal around a shallow dimple. This doesn't happen very often.

Of course if the peak pressure's way too high, that can cause primer cratering when all else is perfect.

[David Bachelder]

May sound stupid, but make sure your primers are fully seated. Clean the pockets or do whatever you have to do to make sure the reloads don't rock when set on a flat surface.

I had a similar situation with 30-06 reloads and found the "proud primer" problem. After breaking the loads down, lowering the resizing die to where the press handle breaks over then re-seating the primers solved everything.

[hooligan1]

It's a Savage 111, and maybe the firingpin spring assembly isn't adjusted correctly. Thank you very much fellas.