Re: Unsafe pressure w/ Yugo 48A?

05 February 2004, 03:27

Major Caliber

Quote:

wildcat junkie,

Quote:

8x57 ..24" barrel..200gr Nosler Partition.. * 50.1gr IMR 4895 2713fps @ 60000psi

I just posted somewhre else:
"8x57 .. 29" barrel ... 200 gr Match King... 47 gr IMR4895 2630 fps"

and I got comments like:

" Clark, that's real nice, but remind me to never shoot any of you're reloads! Nevermind, I think I can remember!"

"Your reloading practices are just plain unsafe. Post all you want as this is a free country but do us all a favor and don't post your recipes."

I AM glad this is a free country and we can develop loads, post them, and call each other "unsafe".

Here is the rest of Clark's post about his reloads.

Quote:

Win 8x57 brass, WLR primers, seated with RCBS, 47 gr. IMR4895 bulk all loads were seated so long that unfired extraction resulted in spilled powder:
n) 200 gr. Sierra Match King, new brass, 3.625" with Sinclair 30 cal nut, 1" 5 shot group at 100m [first 4 shots were 1/2" and I made the whole range stay hot to wait for my 5 th. shot], flattened primers
2618, 2633, 2649, 2623, 2650, 2626, 2638 fps

Spilled powder, and flattened primers! That and Clarks past reloading post's, are the reason for my comment's.

05 February 2004, 07:45

Ricochet

8mmFan, I love your disclaimer!

05 February 2004, 07:42

z1r

Quote:

Here is the rest of Clark's post about his reloads.

Quote:
--------------------------------------------------------------------------------

Win 8x57 brass, WLR primers, seated with RCBS, 47 gr. IMR4895 bulk all loads were seated so long that unfired extraction resulted in spilled powder:
n) 200 gr. Sierra Match King, new brass, 3.625" with Sinclair 30 cal nut, 1" 5 shot group at 100m [first 4 shots were 1/2" and I made the whole range stay hot to wait for my 5 th. shot], flattened primers
2618, 2633, 2649, 2623, 2650, 2626, 2638 fps

--------------------------------------------------------------------------------

Spilled powder, and flattened primers! That and Clarks past reloading post's, are the reason for my comment's.

And here are some more reasons to avoid clark's reloading advice.

Clark shooting primers loose:

http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=224451&Forum=,

Clark shooting more primers loose:

http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=219607&Forum=

Clark shooting bragging about shooting primers loose:

http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=216666&Forum=

Clark confessing to blowing up lots of guns:

http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=214914&Forum=

Clark designing his own proof loads:

http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB5&Number=198196&Forum=

This is some one whose reloading advice I would not heed.

05 February 2004, 04:18

denton

Quote:

Where does the 60,000 psi threshold come from?

That's a real good question.

For commercial firearms, SAAMI is the official repository of pressure specs in the US (CIP in Europe). They do have pressure specs on the 8x57, but data.....???

In general, if we know pressure, we can figure out how much steel it takes to constrain that pressure. With peak pressure, and a few other numbers, it's not hard to figure the thrust applied to the bolt, or the "hoop strain" applied to the barrel.

If the hoop strain, or the bolt thrust are greater than the yield strength of the steel in those places, the firearm will fail. If the steel is repeatedly stressed close to this limit, it will eventually fail. There is a point, below which, repeated stressing of the steel leaves no obvious change. You have to operate somewhere well below that point. As you exceed that point, damage escalates rapidly.

Now, most people figure the SAAMI spec on the 8x57 is ridiculous, IF you have an action that is of the right make and vintage. There have been many, many of them rebarelled to 30-06, and operated at full 30-06 pressures. So we have good emperical evidence that 58-60 KPSI is safe, even if it exceeds the SAAMI spec. At that, though, there are models that have a reputation for kbooms. Not all of them were made to the same standards.

I have a Turkish Mauser with an '06 barrel, that is instrumented with a strain gage (fairly cheap these days). The hottest load I run is Hodgdon's max load for a 180 grain bullet, and it runs 56.4 KPSI. That leaves some room for variation, and gets me dang near 2800 fps.

With a Yugo action, I don't think you can rechamber for 8mm-06, but you could probably get a worthwhile boost in power if you could do some sort of "Ackley Improved" 8x57. I'll bet Wildcat Junkie knows something about that.

05 February 2004, 11:42

8mmFan

Glad you guys like the disclaimer! I'm pretty sure no one will be able to point their finger at ME as the cause of their shrapneled rifle with a disclaimer like that. I laugh harder when I read it now than I did while I was typing it. Oh, well, funny that one would even consider it necessary to put it in. Still, I figured it not only would protect me but also protect the AR site as well, from some bozo with a hot-to-sue attorney, who actually does have an exploded rifle and decides to sue AR just to line his pockets. Would love to see the look on the jury's face as that disclaimer was read out in the courtroom!

In an earlier day, when personal responsibility was a given, you wouldn't even think of typing something like that. Guess we can thank the lawyers...

I hereby freely and knowingly release all rights to and use of the disclaimer to anyone who wishes to use it

8mmFan

07 February 2004, 06:39

Wstrnhuntr

Quote:

Westernhunter, asdf came up with the idea of using a chronograph for calibrating the pressure device already.

I strongly advise not do go this lane as it is a dangerous one.

With milsurp and factory ammunition, muzzle velocity mostly is the product of an unknown powder's combustion.
Using a chronograph, the shooter might get the impression to have detected the secrets of the powder just by applying a sophisticated technical procedure.

He has not, as the burn characteristics of powders are too different from each other: while a slow powder has a flat pressure curve, a fast powder has a (dangerous) steep one.

Right you are! I must add emphasis to the fact that I view the chronographed millsurp ammo as "MAXIMUM" loads and that was very likley done with powder developed especially for said cartridge. As with reloading for any gun, ALL load development precautions and methods are still applicable.

There are some exceptions that allow one to safley load "beyond the norm" and gain exceptional velocities. One is the use of newly developed powders, and then there is the rare "fast barrel" that seems like it had a magic wand waved over it and excells with almost any load. But in my humble opinion, the most frequent occurence of "exceptional velocity" outside of the norm is usually going to be accompanied with exccesive pressure which can be either immediatley apparent or hidden.

All rifles are individuals and some variation is to be expeted. This fact forces all manufacturers of ammunition to err on the side of caution a wee bit which also can give handloaders an edge. But I agree that the 3000 fs + 180 grain load is most likley being done with concealed excessive pressure and eventually something is going to give. You dont want your head next to it when it does..