Too much preasure

KDX

KDX

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I tried some 24gr, 25gr and 25.5gr (Benchmark with 53gr Hornady Match HP) loads today and it looks like the primers are starting to flatten out a bit on the 25.5gr ones. This I have read is a sign of too much preasure. The neck of the shell is still getting a little bit 'blackened' which I was told was a sign of a weak load because it wasn't sealing. Is it the Winchester 5.56 brass that I'm using that is causing this? I did shoot one group that had an outside measurement of 0.618" which is probably pretty good I guess.

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IMO there is NO reliable pressure indicator envolving case measurements, or primers. There are hard primers, and soft, thick cases and thin, hard brass and soft. Loose chambers and tight. Too many variables for anything to be absolute.

That said, a primer that has it's corners squared out is a fair (not absolute) indicator that you have a VERY stout load, and blackened necks is USUALLY caused by low pressure.
For example, the 303 british factory load put out by CIL in the late 60's under the Dominion name, would frequently have very flat squared out primers, and in a loose Lee Enfield, have close to a head separation, making the brass unusable to reloaders.
 
Just as a note of caution: By the time you see overt signs(primer flattening) of pressure you are already most likely 20 to 25% over the SAAMI pressure standard for that cartridge. Of course there are exceptions like JYC explained.
The best indicator is actual pressure testing equiptment, the next is a chronigraph. If you are out of the theroretical velocity range your loaded too hot.
A few hot ones probably wont do too much harm, but a steady diet of grossly over maximum pressure loads(5%+) could very well cause cumulative metal fatigue.
Since your using milspec brass and the case capacity is less than commercial brass, and heeding the warning to reduce all loads in Milspec brass by 5% that means your theroretical top load should be about 24 to 24.25grs.
Chances are your operating at or about 57000CUP of pressure, indusrty spec is 52000CUP.
 
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Flattened primers are only one indication. Where are your loads in respect to published ones? What do they chrony at?

Necks should normally see some soot, the shoulders shouldn't. If there's no soot whatsoever on the necks, then you probably have a tight chamber, and might want to consider neck turning.
 
I used 25.6 grs Benchmark with the Nosler 55 grain BT, worked well and no signs of overpressure ever. This is the max load from Hodgdon. 3250 fps in a 22" tube (1:12)
 
The biggest consideration is whether or not it is too high in your rifle, not someone else's. So saying, if you chrono your loads, what is the SD. A load that is a bit milder, but more consistant is the one to go for over the hottest possible listed in a manual.
 
When your primers burst! and the hammer on your revolver recocks itself !

Presure could be a tad high so ive been told :D
 
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John Y Cannuck said:
IMO there is NO reliable pressure indicator envolving case measurements, or primers. There are hard primers, and soft, thick cases and thin, hard brass and soft. Loose chambers and tight. Too many variables for anything to be absolute.

That said, a primer that has it's corners squared out is a fair (not absolute) indicator that you have a VERY stout load, and blackened necks is USUALLY caused by low pressure.
For example, the 303 british factory load put out by CIL in the late 60's under the Dominion name, would frequently have very flat squared out primers, and in a loose Lee Enfield, have close to a head separation, making the brass unusable to reloaders.
Click to expand...


Not absolute I'll grant, but if I gotta quit my range session,take the gun home, the primer has already fallen out of the fired case,and pound on a wooden dowel to get the case rear out,then an extractor for the rest of the shell..Would that be a case telling me pressure is up....EEEYYYYAA MAYBE. So I think a few steps back from that insane pressure we can start using some of those as indicators,,NO?..

To answer the question a slight flattening is no prob at all. The blackening around the case mouth just means that your case neck is headspacing well and allowing a small portion of gas to the neck...Not to worry. If it were a straight wall I'd say go to a faster powder if your blackening. Sounds to me like your doing things pretty much dog on. Buy yourself a chronograph,it removes 98% of the guess work. Back to the primer,just see if the new one is snug. If it is,your good. The horizontal shift of that one shot could be breeze if there was any. And more than guys think the grip you take on the wrist must be light and consistant and the position of your trigger finger the same every time
 
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