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Joined: Jan 2014
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Sidelock
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Sidelock
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I received some Nice Shot last week and used 4 12ga shells. Of those, 3 did not open properly. The crimps were basically blown off. How does this effect pressure and the pattern?

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Sidelock
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May not be directly related, but Tom Roster checked the velocities of plastic hulls which were reloaded until they failed. There was no change in velocity between the first reload and the last

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Sidelock
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I suspect it is OK, I have had LOTS of Federal Steel hulls separate
at the crimp when shooting in cold conditions.

They still kill ducks smile

Mike


USAF RET 1971-95 [Linked Image from jpgbox.com]
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"IF" the crimp did not open at all you would of course have a closed cell pressure which would be astronomical. Any increase in resistance to the crimp opening over normal will increase the pressure. The question here however is was the hull itself just weak & broke easier than opening the crimp. If this be the case there was likely no increase of pressure.
I find that No Change in velocity from an as new shell with firm crimp to one ready to fail a Bit Hard to Swallow.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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I too find it difficult to believe that a a new factory shell with a tight firm crimp had the same veloicty as a old used shell. The factory new shell will develope more pressure hence more veloicty, every thing else being equal.

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Sidelock
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I agree w/Miller's skepticism.

Its been a long while ago, but I want to recall that an article in Wolfe publications Handloader early on that dealt w/pressure & velocity testing repeated reloading's using an original AA CF 12ga. hull and it found that as the number of reloads increased there was a significant drop in recorded pressures as well as velocity. I know, there is no direct corollary between pressure and velocity and that was NOT being implied, rather it was simply observed as I recall. Hey, like Russ always said, I could be wrong. It may have been an article dealing w/crusher methods as well, i.e., LUP, not psi.

I cannot tell from the OP if it was factory loaded ammunition or something that had lead originally and the Nice Shot was used as a replacement. If it was the latter, that is NOT a proper application w/o tested data suggesting such use and it is an open question as to the pressures involved.

I've shot a lot of Bismuth, tungsten iron, Heavi-shot & steel and while the factory crimps on some of it has been 'butt ugly', I've never seen a crimp blow off, even in below freezing weather. Just my experience, not refuting Mike's at all. I don't shoot many Federal non-toxic loads though their newer Black Cloud loads are clearly VERY effective. I'm just not into that level of punishment;-)

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I doubt that the hull has sufficient strength in the walls to gen up enough force to hold the shot long enough to cause much, if any, increase in pressure. The hull should fracture at something like 650-700 psi chamber pressure. This would be quite early in the burn. I'll post calculations if anyone is interested.

The pattern might be a different story. If the hull ruptured below the shot column, you might have a "sortaslug." If the hull ruptured at the crimp base, I'd expect it to act like an overshot wad and spin off shortly after muzzle exit with minimal effect on the pattern.

Back in the bad olé days, I loaded AA's until they fell apart. I never noticed any deterioration in clay breaking between new and rag. But, I've never run pressure tests, either.

DDA

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Sidelock
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If continued reloading results in decreasing pressures/velocities due to a weakening crimp, would a shot card help offset that decrease? My recollection is that shot cards do not have any material impact on pressure.


Such a long, long time to be gone, and a short time to be there.
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I think most of us loaded AA hulls beyond their useful life back when. I'd load them w/AA452 until there was almost no mouth left and what was, was both split & burned & they still broke correctly pointed skeet targets. No argument here about that.

Empirically, I observed that reloaded hulls using the Ljutic Mono Wads cut from some form of fiber board [I think] would grab the inside of previously fired AA hulls like they were super glued upon firing and stretch the hulls over 1/8" w/boring frequency. Those same loads almost always ironed any fold memory from the hull's mouth & when viewed from the side the hull's mouths were clearly stretched in a non-uniform manner. Some of them were off sounding on occasion as well, not always, but the hull stretching was. Same loads in a paper hull [Winchester, Federal or Remington] never exhibited that issue or sounded 'off'.

There was an article several years ago where someone had tested for pressure differences with differing crimp depths and found significant increases with increased crimp depth. I don't recall who wrote it or where it was published, but I remember it caused quite a stir at the time & I still see refs to that effect. Testing was done by an independent lab for the author. I do not believe there was much velocity dif. noted. and that it was done using once fired CF hulls.
Just saying.

Conventional 'card' wads? I'd not think they contribute anything significant to pressures generated.

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If they are like the 20 gauge loads I just received, they appear to be made up with new Cheddite hulls with a star-type crimp. I have not fired any of mine. The boxes are marked, stating that the cartridges are loaded by Classic Shotshell/RST.


GMC(SW) - USN, Retired (1978-2001)


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