Test Loads for 9mm... Pressure Signs

[Sinjin]

Hello, everyone. First post. I just recently started casting boolits for my 9mm XDm, and this forum is a real find! I'm having some difficulties and am hoping that some of the experienced boolit casters here may be able to help.

I'm using a Lee TL356-124-TC mold, HP38 and mixed brass. I know mixed brass is not recommended, but I did measure and sort by case length. It was my hope that I could arrive at an OAL that would provide sufficient tolerance for some variation in case length.

I loaded and fired test rounds (hand fed) with charges ranging from 3.5 to 4.5, and started seeing flat primers, intermittently, at around 3.9 or 4.0, which was sooner that I expected. I presume I'm getting pressure spikes, and am trying to identify and eliminiate the cause. I read, in multiple places, that 9mm can be very sensitive to the depth that the bullet is seated, and am currently speculating that my boolits are seated too deeply. I don't think that I'm compressing the powder, but my measurements suggest that there is very little spare room in the case, especially for the larger test loads. The only thing I can think to do, at this point, is try a powder with a lower VMD, like HS-6 or WSF, to allow extra room in the case for case length tolerance and set back during feeding. Am I on the right track, here? Has anyone else shooting 124gr or bigger boolits in 9mm had trouble with HP38?

I had to seat the boolit so that the base of the cone was at, or even slightly below, the rim of the case in order to insure that the cartridge would chamber reliably in my XDm. Is this typical, or am I doing something wrong? I've read that pressure can spike if 9mm boolits are seated too deeply. I've also read that pressure can spike if boolits are seated too close to the rifling. Given the size of the charge I want to use, the density of my power, the restricted volume of the case, and my chambering issues, I feel like I'm falling short of having any spare room for adjustment. Is this a common dilemma when loading cast for 9mm, or, again, am I doing something wrong or missing something?

TIA,
Sinjin

[Ricochet]

OAL length measurements are only useful when comparing bullets of the same shape. The problem with pressure is the volume in the case, which is going to be determined by where the base of the bullet is inside the case. I use that boolit in 9mm, and I find it generally has to be seated right with the truncated cone ogive starting at the case mouth to let the cartridges chamber properly. Compare the outline of a rounded nose style 9mm bullet and this TC boolit and I think you'll see that the ogive of the round nose extends outside the outline of the truncated cone. That means more metal outside the case at a given OAL, thus more room inside the case. You may have to back off a bit on loads developed for the round nose to use them with the truncated cone.

[KYCaster]

"The only thing I can think to do, at this point, is try a powder with a lower VMD, like HS-6 or WSF, to allow extra room in the case for case length tolerance and set back during feeding. Am I on the right track, here?"



If you're getting ANY set back at all, it's too much. It doesn't make any difference what powder you use, set back during feeding will increase the preasure.

Crimping over the ogive will make the situation much harder to control since you're depending on bullet pull friction rather than the crimp to prevent the set back.

You may find that the problem is intermittent because of the difference in hardness and thickness among brands of brass. I'd load several dummy rounds in each brand of case you have and run them through the gun to see if that will shed any light on the problem.

Good luck and be careful.
Jerry

[mike in co]

first all pistols are different. second with no oal listed not too much help to offer. third even if you shoot mixed cases , do you intial testing with sorted cases. buy a cheap lee case trimmer.

this maybe a place where the lee factory crimp die would be of help.

mike in co

[Echo]

When you discuss seating deeply so the round will chamber, are you speaking of chambering from the magazine, or dismounting the barrel and chambering by hand? My experience is that semi-auto pistols will slam the round home even if the boolit makes contact with the leade, and that is not necessarily a bad thing - it reduces endplay, making ignition more reliable.

Anyway, flat primers tell you to back off...

[KCSO]

The only thing flat primers will tell you is that the primers are flattening. I would rather try and measure case head expansion and you can't do that with mixed brass and used brass. You need to develop maximuum loads with new or once fired brass of the same headstamp and preferably lot run. Primers can flatten from too loose a pocket as quick as anything else, hence unless you have cases with exactly the same primer pocket tension you have no basis for comparison. Case head expansion can be measured IF all your cases are the same, same make, same lot number and same number of firings, I also seat the primers with a hand tool to try and judge the tension in the primer pocked. I try to use a factory fired case of the same headstamp as a comparator and will shooot for no more expansion than that case. Say if I am working up a load in a federal case i will use a federal factory HP for comparison.

[Sinjin]

Thanks to everyone for the feedback.

Ricochet, that makes perfect sense. So, is it safe to say that it might be impossible to safely achieve the same velocities, with a TC, that can be achieved with an RN, due to the loss of case volume.

KYCaster, I hand fed the cartridges through the ejection port for this initial round of testing, just to temporarily eliminate setback as a variable. But I did load a magazine and run them through the action by racking the slide, and then re-measured the length. Almost every round measured one or two thousandths shorter. Perhaps I'm under or over crimping them? I have read other posts in which people opined that one should only crimp just enough to remove the flare. If that is, in fact, correct, then isn't friciton between the sides of the bullet and the inside of the case the only thing preventing setback? Your recommendation to sort my cases and attempt to correlate the problem to the brand sounds like a good one. I'll do that as my next experiment.

Mike, I have both of those tools, but I haven't used the case trimmer yet. Opinions seem to differ on how important it is to trim pistol brass.

Echo, I was referring to inserting the round into the chamber of the dismounted barrel. If I understand you correctly, having the bullet contact the rifling when it chambers is not a problem? Others have advised me to avoid this condition, indicating that it can cause the pressure to go up dangerously.

KCSO, thanks for the input. I did not know that loose primer pockets could result in flattened primers. Where do you measure case head expansion? Just above the extractor groove? If, by "factory fired", you mean a case that was fired by the manufacturer of the brass, where does one obtain such a thing? FWIW, I'm not interested, at this time, in developing a maximum load. I am perplexed by the fact that the primer flattening, which I, perhaps wrongly, assumed was due to overpressure, occured at much smaller powder charges than I expected. I don't have any new brass on hand. For that matter, I can't really know for sure that the brass I purchased, which was advertised as once-fired, is what it was advertised to be.

[mike in co]

you still did not list an oal ......

[Linstrum]

Case length is of paramount importance in the 9mm Parabellum and nearly all other straight-sided rimless cartridges because they headspace on the case mouth. If the case is too short it could prevent the firing pin from striking the primer hard enough to set it off, and if the case is too long it might crimp the projectile in harder or prevent the bolt from going into battery.

I use Blue Dot in 9mm, although it is temperature sensitive with low pressure in real cold weather. I have also used Unique with good results, too.


rl626

[Ricochet]

The 9mm isn't a straight case, though. It's quite tapered. I'm not sure if it really does headspace on the case mouth. I do the "trial fitting" in a barrel removed from the pistol, in any case.

[mike in co]

Case length is of paramount importance in the 9mm Parabellum and nearly all other straight-sided rimless cartridges because they headspace on the case mouth. If the case is too short it could prevent the firing pin from striking the primer hard enough to set it off, and if the case is too long it might crimp the projectile in harder or prevent the bolt from going into battery.

I use Blue Dot in 9mm, although it is temperature sensitive with low pressure in real cold weather. I have also used Unique with good results, too.


rl626

technically you are right, in reality most primers are ignited from the case being held back by the extractor.
the crimp variation caused by varing case length will have some affect, but as others have said, case neck tension is a bigger factor.

i will not argue the points.....i simply taper my cases back to about one thou below seated dia.

i do have an m59 s&w that was hand fir to space on the mouth, but no other gun and i got plenty.

mike in co

[HORNET]

Sinjin, One thing you might not know is that flat primers occasionally can happen with mild loads and rimless straight cases, especially if you're NOT headspacing on the boolit. The firing pin drives everything forward in the chamber, creating clearance between the case head and the breech. The primer then ignites and can be moved backwards from the bottom of the pocket. The powder then ignites and the pressure drives the case back to the breech, flattening the primer. This is especially evident if primer pockets are a little (or lot) loose as KCSO mentioned in post 6.
Seat them so the boolit contacts the rifling and establishes the headspace, give them light crimp, and retry. You ight want to check some of the .45 ACP threads: same principle, different caliber. Just make sure that they'll feed seated that long.

[Sinjin]

you still did not list an oal ......

mike,

The OAL was 1.050.

[Sinjin]

... Seat them so the boolit contacts the rifling and establishes the headspace, give them light crimp, and retry. You ight want to check some of the .45 ACP threads: same principle, different caliber. Just make sure that they'll feed seated that long.

HORNET,

I did not know that. I think that technique would also provide a degree of insensitivity to case length. Just to be entirely clear, having the bullet in contact with the rifling is not dangerous?

[jeff423]

I've found that 1.158 OAL has worked well for me in both 115 gr and 125 gr FMJ and LRN bullets.

Jeff

[KYCaster]

HORNET,

I did not know that. I think that technique would also provide a degree of insensitivity to case length. Just to be entirely clear, having the bullet in contact with the rifling is not dangerous?

As long as you're not working near max pressure. It takes very little pressure to engrave the rifleing.

Jerry

[NickSS]

I use a lot of those TC bullets in my 9mm's and do not have any trouble with any of them. I generally seat the bullet to just before the TC tapper begins and mostly use unique powder with them. I load them to around 1150 fps in my Ruger P89 which is what I chronographed my load in but they work in my Glock, Taurus PT99, Baby Eagle, and Browning HP just fine too.

[mike in co]

can someone tell me the length of this boolit ?

thanks
mike in co

[9.3X62AL]

I don't have that mould, Mike.

I think VERY highly of the Lee truncated cone autopistol boolit designs. I use the conventionally-grooved designs in 9mm, 40/10mm, and 45 ACP. In all these calibers, a sweet spot for overall length seems to be with about .020" of boolit sidewall extending outside the case mouth. This gives an OAL in the 9mm of about 1.125". In several 9mm pistols, this gives very reliable feeding and plenty of magazine column clearance. Your OAL of 1.05" strikes me as being quite short for a bullet of 122-125 grains in weight, and may account for an over-pressure situation in your pistol.

I have never used HP-38, but have used a LOT of WW-231 in the 9mm, and the latter is considered to be very close in performance per grain in a given caliber to HP-38. 1999 data I have on hand from Winchester ammunition gives a start load with 124 grain lead bullets using WW-231 at 3.3 grains for 910 FPS and 23,800 psi, and a max load of 4.0 grains giving 1035 FPS and 32,900 psi. No OAL or bullet nomenclature is given beyond "124 gr Lead RN". In my experience, these loads can be increased cautiously--once a given boolit's working overall length is established. The above loads will function most pistols, though.

Summed up--I think your powder weights are reasonable, but your overall length needs to be extended.

[mike in co]

I don't have that mould, Mike.

I think VERY highly of the Lee truncated cone autopistol boolit designs. I use the conventionally-grooved designs in 9mm, 40/10mm, and 45 ACP. In all these calibers, a sweet spot for overall length seems to be with about .020" of boolit sidewall extending outside the case mouth. This gives an OAL in the 9mm of about 1.125". In several 9mm pistols, this gives very reliable feeding and plenty of magazine column clearance. Your OAL of 1.05" strikes me as being quite short for a bullet of 122-125 grains in weight, and may account for an over-pressure situation in your pistol.

I have never used HP-38, but have used a LOT of WW-231 in the 9mm, and the latter is considered to be very close in performance per grain in a given caliber to HP-38. 1999 data I have on hand from Winchester ammunition gives a start load with 124 grain lead bullets using WW-231 at 3.3 grains for 910 FPS and 23,800 psi, and a max load of 4.0 grains giving 1035 FPS and 32,900 psi. No OAL or bullet nomenclature is given beyond "124 gr Lead RN". In my experience, these loads can be increased cautiously--once a given boolit's working overall length is established. The above loads will function most pistols, though.

Summed up--I think your powder weights are reasonable, but your overall length needs to be extended.

al,
this is why i asked...i get 54k psi......way over max....but with a generic 124....whixh is why i need the actual boolit length.

me thinks there is a reason why he is seeing flat peimers!
where did the oal of 1.050 for this boolit come from and where did the reccomendation for hp38 powder and loads come from ???

its only about 1200 fps...but WAY TOO MUCH PRESSURE.

MIKE IN CO