View Full Version : Reading pressure in flattened primers?
Hi all,
I've posted this in a more specialized online forum, but I thought I'd ask you guys for your opinions, because there's more know-how and less bluster on M4C.net than anywhere else...
Please see the spent cases, in moonclips, below... going from left to right, they're hot, hotter, and hottest.
How badly are these primers flattened? Am I nuts to keep shooting the "hot" load?
(The "hottest" split a case, so I'm not going there anymore.)
Primer condition isn't very helpful on gauging pressure. And mild .38 spl loads will split cases. A chrono is your best bet.
Yeah, I was going to spare you guys are all the messy details...
These are 10mm Magnum (the extra-long wildcat, not the plain vanilla 10mm AUTO), running through a modified S&W 610 revolver.
Based on others' data, I'm basically I'm at/near a max load (16, 17, and 18gr of 2400 under a 200gr JHP, using CCI Magnum LPPs), but I'm seeing 300fps less MV (barely 1,100-1,200fps instead of 1,400-1,500+).
So, based on velocity, the pressures ought to be fine, but I'm not used to seeing primers all smushed up like this, and the split case spooked me badly...
This is a range toy and a "what-the-hell" project, so I'm content with 1,100-1,200fps... I just wanted some reassurance that these don't look like impending-kaboom excessive pressure.
I just happened to be skimming the Ramshot loading data for the 90 gr Atips we're going to mess with, and in the beginning of their pdf, they show a 45 ACP case that was lab fired at like 32k psi.... WAY over max, and the primer looked fine.
Rifle primers tend to read better than pistol.
The split cases can be from the diameter of the chambers in the cylinder and the diameter of the loaded case.
If the cases become work hardened they can split when fired and expand. How thick of a feeler gauge can be slid between the rear of the case and the recoil shield. The greater the gap the further the primer can back out of the primer pocket and the more the primer can look flattened.
Are the cases hard to extract and what is the difference in the loaded diameter and the fired diameter of the case. You could just have "fat" chambers that allow the case to expand excessively.
What does fired factory loaded ammo look like to give you a base line.
At the link below the moon clip thickness can effect the head clearance/headspace. And making cases from rimmed cases is discussed, the 30-30 cases made thicker 10mm cases but the headspace increased. Thicker moon clips and thicker cases might fix the problem. Are you using standard Starline 10mm brass or the longer heavy duty brass?
10mm Auto Rim?
http://castboolits.gunloads.com/showthread.php?235186-10mm-Auto-Rim
The correct headspacing of the 10mm cartridges. The headspace here was measured at .010″.
https://revolverguy.com/psa-40-sw-in-the-10mm-gp100/
https://secureservercdn.net/198.71.233.109/q58.534.myftpupload.com/wp-content/uploads/2018/06/40-SW-in-the-10mm-GP1004-1021x1024.png
Primer condition isn't very helpful on gauging pressure. And mild .38 spl loads will split cases. A chrono is your best bet.
“Reading” Pistol Primers for pressure sign is usually an exercise in futility.
There are better powders available than 2400 for your project Bimmer.
I’d look to HS6 or AA7, AA9. I’m sure there are other, newer powders as well.
Yeah, I was going to spare you guys are all the messy details...
These are 10mm Magnum (the extra-long wildcat, not the plain vanilla 10mm AUTO), running through a modified S&W 610 revolver.
Based on others' data, I'm basically I'm at/near a max load (16, 17, and 18gr of 2400 under a 200gr JHP, using CCI Magnum LPPs), but I'm seeing 300fps less MV (barely 1,100-1,200fps instead of 1,400-1,500+).
So, based on velocity, the pressures ought to be fine, but I'm not used to seeing primers all smushed up like this, and the split case spooked me badly...
This is a range toy and a "what-the-hell" project, so I'm content with 1,100-1,200fps... I just wanted some reassurance that these don't look like impending-kaboom excessive pressure.
Not sure if you are familiar with 460 Rowland so will keep this brief while trying to explain -
Instead of 20k psi like in a 45acp they can be loaded to darn near twice that. To keep guys from accidentally loading and firing those in a regular 45acp handgun the brass is a tiny bit longer than regular 45acp brass. It will not go into battery completely and you will not be able to light that 460 Rowland round off in a regular cut 45acp chamber.
https://www.underwoodammo.com/collections/handgun-ammo/products/460-rowland-230-grain-jacketed-hollow-point?variant=18785710997561 1400fps with a 230 grain chunk of 45acp bullet...
The chambers on 460 Rowland barrels are cut slightly deeper than a regular 45acp to accommodate that brass. You can safely fire the slightly shorter regular 45acp rounds in a 460 Rowland cut barrel / chamber but...
The headspace is not really 'correct' when you do that. The regular 45acp round (and the mouth of its brass) are not headspacing from the cut in the 460 chamber like normal but more or less being held in place by the extractor during firing instead.
When I fire standard 45acp loads in regular 45acp brass (think 5.0 grains of Bullseye powder under a 230 grain FMJ projectile loads) in my 460 Rowland chambered pistol the primers come out pretty flat. From just looking at the primers in that spent brass from that particular chamber you would think by looking at them that something is not right.
The same exact load with the proper length brass shows none of that primer flattening. Loads from the very top of the 45acp +p load data fired with the proper brass for the chamber show no sort of flattening as compared to the short brass for chamber loads...
The split cases can be from the diameter of the chambers in the cylinder and the diameter of the loaded case.
You could just have "fat" chambers that allow the case to expand excessively.
Again, I didn't want to go into extraneous detail, but yes, I have at least one chamber that's too fat.
Long story short: I'm a dumbass, and I wasn't careful enough reaming from 10 Auto to 10 Mag, and one of the chambers is now 0.437" or so, rather than 0.429" (±0.005).
Moonclips make it easy to keep track of which case was in which chamber, and no surprise: I'm getting bulging at 16gr and 17gr and ultimately a split case at 18gr in that one oversized chamber.
Again, this is a range toy and a fun "Why-not?" project, so I'm not beating myself up over it.
(No pictures of the 0.003" mistake, so I won't wind up in the Gun-Smithing Hall of Shame!)
What does fired factory loaded ammo look like to give you a base line.
No such thing... 10mm Magnum is a wildcat.
I did notice, though, that 10mm Auto from Underwood (Verrry hot!) had seriously flattened primers.
DoubleTap does sell some 10mm Magnum, but that's hardly "factory."
At the link below the moon clip thickness can effect the head clearance/headspace.
Right, the cases are head-spacing off the moonclip, not off the case mouth (like a rimmed revolver cartridge).
10mm Auto did that already, and of course .40S&W does, too.
There are better powders available than 2400 for your project Bimmer.
I’d look to HS6 or AA7, AA9. I’m sure there are other, newer powders as well.
I dunno... As far as I know, 2400 is still the standard for magnum revolver rounds.
I've heard of HS6 having weird pressure spikes (and very narrow ranges between starting and max loads), and I don't want to go there.
Besides, I already have 2400, because I load .30 Carbine...
The headspace is not really 'correct' when you do that...
The same exact load with the proper length brass shows none of that primer flattening. Loads... fired with the proper brass for the chamber show no sort of flattening as compared to the short brass for chamber loads...
Hmmm... This is interesting.
I'm wondering if there's something analogous going on in revolvers, and why/how...
It's hard to think of why pressures would spike due to a little extra space in front of the mouth of the case, if that's what's flattening the primers.
(If this were common, then you'd think the guys shooting .38Spl or .44Spl in .357Mag or .44Mag revolvers would've commented on all the flattened primers.)
And one would think that recoil would smash the case back against the breech face (in a pistol) or against the recoil shield (in a revolver) and smush the primer into the firing pin with the same force, no matter how long the case was (regardless of any extra space between the mouth of the case and the chamber's throat).
I guess I could fire some without moonclips, and let them headspace off the case mouth, and see how those turn out...
It's hard to think of why pressures would spike due to a little extra space in front of the mouth of the case, if that's what's flattening the primers.
(If this were common, then you'd think the guys shooting .38Spl or .44Spl in .357Mag or .44Mag revolvers would've commented on all the flattened primers.)
And one would think that recoil would smash the case back against the breech face (in a pistol) or against the recoil shield (in a revolver) and smush the primer into the firing pin with the same force, no matter how long the case was (regardless of any extra space between the mouth of the case and the chamber's throat).
I guess I could fire some without moonclips, and let them headspace off the case mouth, and see how those turn out...
Pretty sure it is not the pressure that is flattening the primers. Have not tried it but I am pretty confident that if I was to take a regular 45acp case, trim it about 1/16th short, and then fire it in a regular 45acp chamber with a standard load that the primers on the spent brass would be flat and appear to show pressure signs that were not really there.
Hope you share your results / findings as you move forward here. Wish you luck with your efforts sir. :)
Pretty sure it is not the pressure that is flattening the primers. Have not tried it but I am pretty confident that if I was to take a regular 45acp case, trim it about 1/16th short, and then fire it in a regular 45acp chamber with a standard load that the primers on the spent brass would be flat and appear to show pressure signs that were not really there...
I'm still unsure/skeptical of this...
If you were right, then every revolver cartridge that headspaces off the rim (or in my case, off the moonclip), would be flattening primers, right?
FWIW, I shoot .40S&W in this revolver, and there's a LOT of space between the case mouth and chamber throat, and there are no flattened primers.
If 2400 is showing pressure go to h110 or lilgun
Yeah, but I already had 2400, and I'm hesitant to bother with different powders.
Also, I hardly crimped those first rounds at all, so much so that they were a bit hard to chamber. Maybe I'll get a bit more mv out of them with a bit of crimp (to 0.421" or so).
I'm going to chrono some more this week...
Coal Dragger
07-23-20, 23:10
I just happened to be skimming the Ramshot loading data for the 90 gr Atips we're going to mess with, and in the beginning of their pdf, they show a 45 ACP case that was lab fired at like 32k psi.... WAY over max, and the primer looked fine.
Rifle primers tend to read better than pistol.
I can confirm that this is the case.
One of my reloading projects a few years ago was using .45 ACP brass in my Freedom Arms M83 spare cylinder. I can positively confirm that primers are not a good indicator of pressure in a pistol. I will not even admit what the loads were, suffice to say they were well into .460 Rowland data but in a .45 ACP case. Primers looked fine, brass wasn’t sticking in the chambers, and no split cases. Remarkably accurate too.
However owning 2 auto pistols in .45 ACP that would be disassembled in short order by those loads I shot them all and haven’t dabbled in that since.
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