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9mm: is crimping always necessary

Discussion in 'Handloading and Reloading' started by Tony k, May 8, 2014.

  1. Tony k

    Tony k Well-Known Member

    I'm new to 9mm reloading, and an overall new reloader (been doing it for less than 2 years). I was using a dummy round to set up seating depth. I plunk tested an uncrimped round in a Kahr CM9 chamber. It dropped in there no problem. I checked the case mouth diameter of the loader dummy round, and it is .378" (my manuals list .380" as standard).

    I know I've got the expander die set for a very light bell, and I'm not shaving bullets when I seat them.

    My understanding is that the "crimp" for calibers that space off the case mouth is only to remove the bell created to facilitate bullet seating. If my case mouth is already about where you want it,is there any reason that I should crimp?
  2. RussellC

    RussellC Well-Known Member

    You are going to get answers going both directions. I do, with the Lee taper crimp, very mild, just enough to remove bell. 9mm is not designed for a full roll crimp, headspacing on the bullet case mouth and all. Taper crimp only removes the bell. You will hear this a bunch too. Your assessment appears to be in line with my thinking, for what ever that is worth!

  3. germ

    germ Well-Known Member

    Yeah, you just want to remove the bell. Not removing it could possibly lead to feeding issues even if they drop test ok. Just depends on your gun.
  4. Blue68f100

    Blue68f100 Well-Known Member

    No. Depending on the bullet base crimp may not be needed. It all depends on how much flare you put on the case. Measure before you seat the bullet. Then if the final measurement is larger you removed it all. With some bullets having a round base no flare may be needed. Since it passed the plunk test you should be good to go.
  5. UziLand

    UziLand Well-Known Member

    Have you done the tap test on finished rounds to see if the OAL remains consistant?

  6. Potatohead

    Potatohead Well-Known Member

    This is the golden nugget ^^^...

    You can possibly/probably get away with it for awhile, but eventually their will be a misfeed in your future???
  7. cfullgraf

    cfullgraf Well-Known Member

    This covers the need to taper crimp pretty well. It just depends.

    Having agreed with Blue68f, i still run my auto pistol cases through a taper crimp die. Most just to make sure any flare is removed. My crimps are pretty light unless the flare gets pretty large.

  8. bds

    bds Well-Known Member


    If you use mixed range brass (and I do), depending on the headstamp/how many times the case was reloaded/whether another reloader trimmed the case, the case length will vary and this will result in different amount of flare on the case mouth.

    Also, not all commercial bullets are perfectly round in diameter. An out-of-round bullet seated in a case without taper crimp will result in an out-of-round case neck which may cause feeding/chambering issue in tighter chamber barrel (That's why Lee made the Factory Crimp Die - to fix out-of-spec rounds).

    For these reasons, I always use the taper crimp die so the finished dimensions are consistent.
  9. KingM

    KingM Well-Known Member

    Pretty much how mine are done. My die is set low enough to fix any belled out to far but most are never touched.
  10. Tony k

    Tony k Well-Known Member

    So I set my seater die to just touch the case mouth on cases that are .750". Loaded up five each of the following:

    Longshot 4, 4.3, 4.5, 4.7 grains
    Powerpistol 4.5, 4.6, 4.7, 4.8, 4.9, 5.0 grains.

    All were mixed cases, cci primers, xtreme 147gr plated rn seated to 1.135.

    firearm: Kahr CM9

    Tested them at 15 yards on my standard 6-8" steel targets. No discerable difference in accuracy for this purpose. All loads cycled flawlessly. I kind a felt like I had 10 acceptable options to go with. I guess If I really want to maximize accuracy, I could group them at 25 yards, but honestly, I don't see the point with something I'm just using for practice.

    The felt recoil was lowest in the 4gr of longshot, but they were all pretty mild.

    The powerpistol burned a little cleaner. The longshot metered more consistenly.

    Today I loaded up 200 rounds of the 4.5 grain longshot load. unless I start seeing feed issues, I'm probaby not going to change my crimping method with this bullet.
  11. HOWARD J

    HOWARD J Well-Known Member

    What you are doing looks good---now push your cartridge against edge of bench or whatever----make sure the bullet does not move any into the case
  12. gonoles_1980

    gonoles_1980 Well-Known Member

    I use a gauge, which I've tested with the barrel of my wife's 9mm. If it drops in easy, it always fits, if it's barely above, it most likely fits, I do a barrel check with those. My 9mm won't fit in the gauge unless I give it a factory crimp, slight taper crimp.
  13. gamestalker

    gamestalker member

    This is an interesting question to which I encountered and discovered a rather long time ago.

    Back when the 10mm came into production, I bought a Lee 10mm die set. Then when the .40 cal came about, I figured I could load for it using my 10mm ONLY die set. The only problem was the powder thru die wouldn't reach the case mouth of the .40 to produce any bell at all. So after some thought, I chamfered the inside of my .40 brass mouths enough to allow a jacketed bullet to seat straight, and without shaving. I haven't belled or crimped a rimless pistol cartridge since.

    Not only dose it save me time and trouble by eliminating the bell and crimping steps, but I haven't had a single issue with bullet set back the result of lacking neck tension since. I don't load lead, so I couldn't say whether or not this process will work with such, but it's worked flawlessly for me with jacketed 9mm, .40 cal, 10mm and all other cartridges that head space on the mouth.

  14. mgmorden

    mgmorden Well-Known Member

    All you want to do is remove the bell. I set my seater to lightly "crimp" (it really is a misnomer in this scenario) the case and it works great.

    Easiest way to do this is to take a freshly resized case and screw the seater/crimper die down until it contacts the case and stops. I usually do another 1/8 turn after that (some cases vary slightly in length, so the extra bit makes sure that a shorter case still gets attention). At that point you're good to go.
  15. bds

    bds Well-Known Member

    It should depending on the amount of chamfering and if you use bevel based bullets. Now I gotta try it.
  16. Blue68f100

    Blue68f100 Well-Known Member

    If your not expanding the case after sizing you will have Maximum Neck tension. As for lead since they are normally 0.001" over size I would guess you will shave lead on seating. I use the PTX die in my LNL but I do a bare minimum flaring of the mouth. The expander is what I like for a more consistent neck tension. If I load lead it will shave every time even with a beveled base. I have to add another 1/4 turn adj to expand so it does not shave.

    I have found with most rounded bottom jacketed bullets you do not need to expand or flare.

    I do have my RP brass separated from the rest. I found that these are normally thinner and produce lighter neck tension. Not a problem if your not expanding. They work good for lead if you have a tight chamber since the wall thickness is normally thinner. Another reason I separate these is that I had primers pierce last summer with RP brass. None of the other brass mfg had this problem. I think it was to the way RP cuts there primer pockets. They have more bevel than all the others.
  17. fiftybmg

    fiftybmg member

    Yes, you should crimp.

    Any reload that receives impact on the bullet in the magazine from recoil should be crimped.

    You will not find any factory ammo that is not crimped.

    You will experience bullet setback if you do not.

    The question should only be how much crimp.
  18. Blue68f100

    Blue68f100 Well-Known Member

    Once Again...Crimp DOES NOT HOLD THE BULLET ... Neck Tension does. TC is just to remove the flaring done to seat the bullet.
  19. gamestalker

    gamestalker member

    Thank you Blue68f100! And yet Once Again, crimping produces absolutely no neck tension with these type cartridges, that being rimless types, 9mm, .40, 45 acp, ect.. Bullet set back is the result of lacking neck tension that is caused of over expanding the mouth, over crimping the mouth, or brass that has thinned out.

    As for jacketed bullets, as long as the mouth has a decent chamfer, I've had zero problems seating jacketed bullets, even those with no taper to the base at all.

    I sure hope you give it a try BDS. For me, it has been the cats meow.

  20. Potatohead

    Potatohead Well-Known Member

    Are you sure? The couple times Ive looked at crimps on factory rds, a few boxes appeared to have no crimp at all..and I wondered if they ever go without crimping. These had no trace of a crimp that my inexperienced eyes could see.. Maybe they're more perfectly executed and harder to see...?

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