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Thread: 9mm Overpressure Due to Crimping Too Tight?

  1. #1
    Boolit Master DonMountain's Avatar
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    9mm Overpressure Due to Crimping Too Tight?

    I have been working on reloading some 9mm Luger ammo lately, and have been having trouble with high pressure signs in the primer even when using starting loads of W-231 or Bullseye powder. Now I am thinking that maybe I am crimping with a taper crimp die too tightly. Is this a problem with these small, high pressure pistol cartridges? I have tried jacketed and powder coated lead projectiles.

  2. #2
    Boolit Bub Pawpaw757's Avatar
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    I think we need a little more info. How much powder, OAL, things like that.

  3. #3
    Boolit Master


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    I wold think that is not your problem. What pressure signs are you seeing? Are you suse your powder measuring/weighing is correct?
    Taper crimp a jacketed bullet. Then pull the bullet and look for distortion in the jacket. If the bullet is distorted you are crimping too much.
    Also if cast are over crimped you may loose accuracy. How due they shoot?

  4. #4
    Boolit Master


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    I wold think that is not your problem. What pressure signs are you seeing? Are you suse your powder measuring/weighing is correct?
    Taper crimp a jacketed bullet. Then pull the bullet and look for distortion in the jacket. If the bullet is distorted you are crimping too much.
    Also if cast are over crimped you may loose accuracy. How due they shoot?

  5. #5
    Boolit Master
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    you really dont need a "crimp". set the die to straighten the bell back out of the case after seating a bullet. that will almost surely give enough neck tension to hold the bullet fine.

  6. #6
    Boolit Grand Master
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    Taper crimping does not secure the bullet in such a way that it “causes” high pressure.

    “High pressure signs in the primer” are notoriously unreliable. If the chronograph shows acceptable velocities you are not experiencing unacceptable pressures.

    The real problem is that you are placing faith in information that likely means nothing and contradicts what is known. Get better information that actually tells you something. Tell us something more relevant about loading particulars. Then get back to us.

  7. #7
    Boolit Buddy
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    Could be anything; perhaps an undersized firing pin or related issue causing extrusion (& even shearing) of the primer cup - have seen tons of once-fired brass exhibiting this. Really depends on what 'pressure signs' you're seeing ?

  8. #8
    Boolit Grand Master tazman's Avatar
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    Quote Originally Posted by DonMountain View Post
    I have been working on reloading some 9mm Luger ammo lately, and have been having trouble with high pressure signs in the primer even when using starting loads of W-231 or Bullseye powder. Now I am thinking that maybe I am crimping with a taper crimp die too tightly. Is this a problem with these small, high pressure pistol cartridges? I have tried jacketed and powder coated lead projectiles.
    A couple of years ago I got a batch of primers that showed high pressure signs and even had pierced primers part of the time with loads I had been shooting for years. It turned out to be a bad batch of primers. I switched primer brands and the problem disappeared immediately.

  9. #9
    Boolit Master

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    To the OP: Does factory ammo show the same symptoms? If it does, you have a gun problem, not an ammo problem.
    Remember: Ammo will get you through times of no money better than money will get you through times of no ammo.

  10. #10
    Boolit Master DonMountain's Avatar
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    Quote Originally Posted by 35remington View Post
    Taper crimping does not secure the bullet in such a way that it “causes” high pressure.

    “High pressure signs in the primer” are notoriously unreliable. If the chronograph shows acceptable velocities you are not experiencing unacceptable pressures.

    The real problem is that you are placing faith in information that likely means nothing and contradicts what is known. Get better information that actually tells you something. Tell us something more relevant about loading particulars. Then get back to us.
    I guess this pretty much covers everything then. And I appreciate all of the help from you-guys. I will just ignore the flattened, cratered primers and the occasional stove-pipe in the chamber from loadings of powder that are at the bottom of the list in the books. The Hornady and Lyman Cast Bullet Manuals are obviously in error, so I will just ignore them too as being probably wrong. I have tried three different pistol primers and one small rifle primer and they all produce the same results. But factory Winchester rounds I bought from WalMart shoot just fine and have none of these signs. No flattened primers or problems ejecting. So, its not a gun issue as it is a brand new gun. Not a problem until I reload these same cases. But I guess I am just looking at it from a bad perspective and just need to ignore what I thought was a problem. As I said before, thanks for all of your help in working out this issue.

  11. #11
    Boolit Master
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    The crimp is not the issue. Have you tried any other loads that are not at minimum?

  12. #12
    Boolit Buddy glockfan's Avatar
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    why don't you post the load you use: boolit weight,powder type and charge , COAL....this way an accurate opinion can be exposed.

  13. #13
    Boolit Bub
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    I use 3.5 gr of BE with pretty good results in my Glocks. That's with both cast and jacketed. I will admit that in my younger days I was more liberal with the powder, and I see that some say primer signs are not a big deal, but they were to me. I liked my guns and my digits so I backed off. no more major 9 for me.....

  14. #14
    Boolit Mold
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    Quote Originally Posted by DonMountain View Post
    I will just ignore the flattened, cratered primers and the occasional stove-pipe in the chamber from loadings of powder that are at the bottom of the list in the books. The Hornady and Lyman Cast Bullet Manuals are obviously in error, so I will just ignore them too as being probably wrong.
    I am not sure if it is meant that way, but your reply sounds pretty offensive to me.

    No one said you should ignore flattened/cratered primers but primer signs are hard to impossible to read, not only do they differ between brands but also between guns. So far you have given us very little information to go on, post some pictures or load data maybe?
    Stove pipes are a typical symptom of under-powered loads, up your charge a bit and the problem will go away. Whatever you are seeing on your primers are not overpressure signs if you also get stove pipes.

    A primer does not know it in what cartridge it is fired, and what the max. pressure is. How would this be a reliable indicator?

  15. #15
    Boolit Master
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    A thought that may be a bit far out but here goes. Is it possible that you are putting so much crimp on that you are actually reducing the mouth diameter enough so you are losing your headspace? This would cause the FP to drive the case forward into the barrel a bit till either the case finally stopped at the throat or, more likely, the extractor stops the forward movement of the case in the chamber. This would cause the primer to back out a bit upon firing and then as the pressure builds the case would move back against the breech face causing the flattened appearance of the primer.

    I have seen this many times with rifle reloads when the reloader did not adjust the sizer die properly. I don't know whether it can happen with a pistol or not but would be inclined to think it could.

    Regarding the post that said no crimp was required, I DISAGREE totally! Although it doesn't take much of a crimp, anything to keep the bullet from moving into the case while transitioning from the magazine to the chamber is important.

    Just a personal thing, but I hate 231. If it was the only powder available to me, I believe I would quit shooting pistol altogether.
    Liberals don't know they're stupid in the same way a fish does not know it is wet. It is just their natural state of being.

  16. #16
    Quote Originally Posted by DonMountain View Post
    I guess this pretty much covers everything then. And I appreciate all of the help from you-guys. I will just ignore the flattened, cratered primers and the occasional stove-pipe in the chamber from loadings of powder that are at the bottom of the list in the books. The Hornady and Lyman Cast Bullet Manuals are obviously in error, so I will just ignore them too as being probably wrong. I have tried three different pistol primers and one small rifle primer and they all produce the same results. But factory Winchester rounds I bought from WalMart shoot just fine and have none of these signs. No flattened primers or problems ejecting. So, its not a gun issue as it is a brand new gun. Not a problem until I reload these same cases. But I guess I am just looking at it from a bad perspective and just need to ignore what I thought was a problem. As I said before, thanks for all of your help in working out this issue.
    Without the load and specs, everyone is just guessing.

    I could almost guarantee everyone here has loaded for your bullet weight and with the powder you've listed. I know I have. But I'm not going to speculate until you give the specs of the load. You are getting attitude with folks trying to help and are not giving us the proper information to do so.

    Something seems strange here.

  17. #17
    Boolit Master
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    Please provide load data. Powder and load/grains, Bullet weight and type.

  18. #18
    Boolit Grand Master






    Lloyd Smale's Avatar
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    never seen crimp cause excessive pressures. Powder charge and seating depth cause 99 percent of high pressure problems.
    Soldier of God, sixgun junky, Retired electrical lineman. My office was a 100 feet in the air, closer to God the better

  19. #19
    Boolit Master
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    Data is a guide,lower you powder and see what you got. Like stated need more info on it all.Work with the powder otherwise.
    Life Member of NRA,NTA,DAV ,ITA. Also member of FTA,CBA

  20. #20
    Boolit Master
    contender1's Avatar
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    "never seen crimp cause excessive pressures. Powder charge and seating depth cause 99 percent of high pressure problems. "

    ^^^^^THIS^^^^

    9mm is a very depth sensitive caliber. You mentioned using a taper crimp,, as it should be. But OAL combined with the types of powder,,, can be the issue. Win 231 & Bullseye are both fast burning powders. My GUESS would point heavily to a bullet seated too deep.
    You have mentioned those 2 powders, and different primers, along with the crimp. The one thing I do not see you have tried is a different seating depth. Even .010 can make a big difference.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check