reading 9 mm primers for pressure

[c east]

Load is 6 gr herco behind 124 gr XTP 1.060"

Primers are flatten with a little cratering...The primer are Labeled for rifle and high pressure pistol...I know 9mm run high pressure but this looks steep...Most 357's and 44 mag primers look like this but with no cratering....Comments please...I'm suspecting the fireing pin hole a little large...Charlie

 

[c east]

Put some factory 115's thru it....Flattened the primer but no cratering....Will reduce the load to 5.5grs....Charlie

 

[cjw3]

Pics would help. I don't know what "high pressure pistol" primers are, but if you are getting cratering using rifle primers I would bet those loads are a bit warm. Do you see the cratering with standard pressure factory loads?

I found your load, or close to it (6.1 grains-MAX) in my old Lyman manual but it was listed for a 121 grain cast bullet. Also, 1.060" is pretty short. It seems like you might have a couple of things going on that could be running your pressure up.

Not too long ago I ran across a batch of that old Norinco 9mm 124 grain stuff. I got cratering with it in my Ruger P95 and I'm positive it was due to higher pressure. They had more recoil than domestic ammo of the same bullet weight. The Ruger ate them like candy, although a few needed an extra hit or two from the firing pin. Hard primers.

 

[MichiganScott]

I will probably get flamed, but you can't read pressure from primers. The metal will not flow until you get well above safe levels.

There are too many variables like primer hardness, brass hardness, headspace, firing pin size, firing pin hole size, etc., to be able to read anything.

 

[H Richard]

Especially since Winchester makes primers for Standard OR Magnum loads. Primer thickness varies from one maker to another.

 

[OKFC05]

Guessing you're above 35,000psi with that short seated bullet, based on an old chart for Herco and 124gr jacketed. Suggest seating out at least 0.100" more.
You can get more speed without going over pressure limits with Power Pistol instead of Herco.
I've seen pistols blown up with loads where the primer looked normal, because straight-walled pistol cases don't show pressure signs like bottleneck rifle cartridges do.

 

[garbler]

This is a bit scary but correct me if I am wrong. Did you start this load with 6.0 grs of Herco and your now thinking about working your back down the pressure ladder ? If this is correct you are going at this the wrong way. Back off 10% from the published loads and work back UP in increments

I agree with Michigan Scott that technically you cannot accurately determine real incremental pressure information from the primer. You can however easily tell when you have passed over into the red zone by the primer and case head measurments or extraction. I can say this, though it sounds like I am contradicting myself, but after a while you can learn to read the signs with the primer. When primers first start to flatten it will happen in steps but only if you load in steps. They fill in the perimeter edge of the primer pocket by flattening more, additional pressure makes them push off past the pocket a bit and finally when things are much to hot the firing pin indent is pushed back out from pressure to look like a crater or you just dropped a ball bearing into mercury.

Reading primers is an acquired skill and not all primers read the same but pretty close. The more you load and shoot the better you will get at looking and seeing when things are starting to come to a boil.

With my rifle cases I measure the case head with a mic. It is the method that Ken Waters used as do many famous wildcatters who don't have a pressure barrel and it is pretty reliable. Of course if the cases are hard to remove you are over the line. Stiff extraction is always a trustworthy indicator that the load is too hot for your particular gun. May not be in another—but it is in yours.

Good luck

 

[mtgianni]

IIRC, 6 gr Herco is not an over book load for a 124 gr bullet. I have used that with the LY 358242. I do not have access to my manual right now but suggest that you check OAL again.

 

[125JHP]

I use that same load with no problem. IIRC the max load is closer to 6.8 or 7, which must be compressed as 6 almost fills the case as it is. My notes show I have gone as high as 6.7 with a Rem 124 JHP.

A picture would help tell how much cratering is going on, I find a little is common in many guns at higher pressures even with factory ammo.

 

[gaijin]

Good luck "reading" primers for signs of high pressure.
Short of having access to pressure testing equipment, your best bet is chronographing the loads, comparing your results to published data with the same components. If you're running 100 FPS faster than Hogden/Hornady/Speer than their top end loads, with the same components; you're over max pressure.

 

[zeke]

What brand and name primer? What case is being used? They all matter. Are the load's velocitys being measured, or guessed at?

While primers may give an indication of pressure increases, they should not be relied on to indicate safe pressure pressure limits, especially with pistol loads. Sure , if ya blow out the primer it is indicative of way over pressure.

 

[glider1]

OAL, seating depth, can make a huge difference in pressure with 9mm. It's probably as important to 9mm as useing the powder charge as listed. Handloader magazine did an article about pressure signs, there conclusion was that they aren't reliable. A chrono is the best way for us to see what a load does, I gotta get one however I seldom load close to max.

 

[Warren Sear]

Ditto what the others said above about the unreliability of "reading" primers.

I will add that if you get sticky extraction from a bolt action rifle, you are way over pressure (over 65,000 psi?). If you are getting it in a revolver, those loads are flat out hazardous. In this case, the OP is shooting the loads in a semi-auto pistol, so he has no way to determine what the extraction is like.

Case head expansion only applies to new cases, and only comes into play, again, at rifle pressures. If you are getting those indications in a pistol or revolver, you are WAY over pressure.

When I first started re-loading I wrecked a brand new Model 19. I followed the data on the old (and foolishly high) Speer manual, all while looking for "signs o' pressure". By the time I noticed them, the forcing cone on my gun was split and the cylinder bulged.

Get your data from a reliable source and adhere to it closely, including overall cartridge length. Get a chronograph, and if you are getting higher speeds than factory ammo, you are over pressure. There is no reliable, objective method to determine pressure for the typical handgun re-loader, and it chaps my --- to see the constant admonitions to "watch for pressure signs" in regard to pistols and revolvers. There are no indications until you are way over the line.