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9 MM Crimp

Discussion in 'Handloading and Reloading' started by Aguablanco, Oct 25, 2011.

  1. Aguablanco

    Aguablanco Member

    So, here I am again, this time regarding crimps. While the loading manuals state that the cartridge is .380 at the neck I have been crimping to .378 and find this dimension a little snug. I have since measured several commercial cartridges and they average .376 and slide in and out of the cylinder much easier. I have no way to measure the shoulder where the case head spaces. My main concern is over crimping and having the case head space on the extractor. What do you guys use for the crimp dimension? Can I crimp to .376 and still be OK?
  2. rcmodel

    rcmodel Member in memoriam


    As you noted, .376" is a pretty fair average for factory ammo.

    And you can't go wrong trying to duplicate it.

  3. bds

    bds Well-Known Member

    Although there are variations in different heastamp case wall thickness, for semi-auto cases that head space on the case neck, I will use .020" more than the diameter of the bullet for determining the amount of taper crimp.

    So, for .355" jacketed bullet, I use .375" taper crimp and for .356" lead bullet, .376" taper crimp.

    * update - sorry had connection issues

    Some factory barrels will tolerate slightly greater taper crimp but ultimately I will use the taper crimp that will allow the finished round to fall freely into the chamber with a "plonk".

    Also, I am seeing more factory target ammo loaded with sometimes larger diameter plated bullets and larger .376" taper crimp.
    Last edited: Oct 25, 2011
  4. Aguablanco

    Aguablanco Member

    Excellent info guys, I really appreciate it. I did feel I could duplicate factory ammo crimp without a problem, I just wanted confirmation. As we all do, I have a significant investment in my guns, and my health, and want to avoid anything going boom in my hands or damaging my guns. I will be going to the .376 crimp on my next loads.
    Thanks for the excellent advice, I can't believe anyone would be reloading and not be a part of this great community at THR.
  5. Deavis

    Deavis Well-Known Member

    on taper crimp, max diameter - 0.003" will serve you very well. It will serve you well for jacketed, lead, and plated bullets. If you look at a chamber drawing for 9mm, you will see that the taper after the shoulder, midway down the leade, is at 0.354", which is less than groove diameter. You are well away from headspacing with only the extractor and you would probably buckle cases with most taper crimp dies far before getting there.
  6. PO2Hammer

    PO2Hammer Well-Known Member

    I don't crimp 9mm.
  7. 1SOW

    1SOW Well-Known Member

    Just be cautious with plated bullets to avoid damaging the plating.
    If I loaded lead, I'd also be careful not to deform the bullets. When making some test loads, "pull" the bullets to check for excessive crimp.

    I've had no problems with 9mm Berry's .356 diameter with the case-mouth at .3765-.377 tapercrimp. This feeds easily (drops in and out of the chamber) in two short-chambered CZ 75's.
  8. beatledog7

    beatledog7 Well-Known Member

    Search works!

    FI went looking and found this thread as I have just loaded my first batch of 9mm. Midway 124gr JHPs (must be somebody's seconds) over 3.9gr Bullseye seated to 1.094.

    Anyway, I like crimping separately, esp. when working a new caliber or a new load. So I seated a couple of these then measured the case mouths: .376, .377. Perfect, and without a taper crimp. I had flared these only a tiny bit, and with the bullets seated they chamber easily in my CZ barrel and measure dead on spec. So, I'm not gonna crimp.

    PO2Hammer, I'm with you on this one.

    BTW, I used a set of Hornady titanium nitride dies, first i've tried of this brand. This was their first use, and all I did to them was disassemble, clean, and reassemble. I normally polish flare buttons and neck mandrels with Flitz, but this flare die doesn't appear to come apart. That said, guess its button didn't need polishing. I like these dies a lot.
  9. edfardos

    edfardos Well-Known Member

    9mm luger cartrige is straight walled. There is no crimp. Set your crimping die to remove any bell/flare you put on the brass prior to seating. Plan on jams or misfires if you deviate from .005" from straight. Too much crimp and the brass will enter freebore (misfire). Too little crimp and you'll have failure to feed. Same goes for 40s&w, 380auto, or anything that head spaces on the mouth of the brass.

  10. PO2Hammer

    PO2Hammer Well-Known Member

    With my jacketed bullet practice ammo I don't even flare/expand the case mouths, I just resize/reprime, charge and seat the bullet. Occasionally a really dented case mouth will prevent a bullet from seating smoothly, but that's about 1 in 500.

    With plated bullets I touch the case mouths with the Lee Universal Expander die. It's a conical flaring tool and it irons out any case mouth dings and I set it to flare maybe .002"-.003" to help seat the thin skinned plated bullets.

    They don't need to be crimped after seating because the bullet has expanded the case enough to make the tiny flare disappear.

    This has worked for me in many 9mm's including Glock, Sig, CZ, Marlin Carbine...
    I use a Redding Competition seater die which help reduce 'skinning' the plated bullets.

    Tests also show this to be the best way to prevent bullet set back, and accuracy sure doesn't suffer. Case life should be extended as well.

    This method probably doesn't work well with progressive presses as you need to hold the bullet as it enters the seating die, but for turret and single stage loading I think it is the best way to make practice ammo.

    For serious ammo I would use a separate taper crimp die and bump the case mouths just to be sure any dings have been ironed out.
    Last edited: Nov 10, 2011
  11. beatledog7

    beatledog7 Well-Known Member

    edfardos, I'm fully aware of all this. That's why I test chambered and measured the case mouths. None deviate more than .002.

    Did you read my post?
  12. beatledog7

    beatledog7 Well-Known Member

    Thanks, PO2Hammer. I use a Hornady LNL single stage press and don't load high volumes. I actually like doing this slowly and carefully; I see no need to turn it into a factory job.

    That effect seems to be exactly what happened for this load. Had I not read your post, I'd be sitting at my bench now picking nits to get the taper crimp right, even though my calibers and my barrel were trying to tell me not to. There's a lesson!

    I could easily reset the die to smooth the mouths, but they don't appear to need it. I'll shoot these and see how they go; if unsat I'll try smoothing them out next time.
    Last edited: Nov 10, 2011
  13. 1SOW

    1SOW Well-Known Member

    Closing the bell is call a taper crimp.
    9mm is straight but "angled/tapered" walls out to the base, not straight vertical wall like a 40cal/45acp.
    With my 9mm Sig and two CZ's, the case and bullet would have to be literally "crushed" evenly to not seat on the case mouth. I won't say it's impossible to do, but it's SURE not an easy mistake to make.
  14. Walkalong

    Walkalong Moderator

    The 9MM is a tapered case. Something that sometimes causes trouble chambering if not sized down far enough on the case.

    The amount of "crimp" is negligible. I never used to measure what I crimped too until folks started asking. I just set up the taper crimp to remove the bell or perhaps a hair more. Shorter cases would have no crimp while the longer ones would get just a hair.

    It would take an excessive amount of crimp to let the case slip past the chamber into the leade. Excessive enough you could easily see it.
  15. cfullgraf

    cfullgraf Well-Known Member

    Yes, 9mm is a tapered case, but the walls are straight.

    Parallel walled and tapered walled would be better descriptions but I guess I could never change years improper nomenclature.
  16. Walkalong

    Walkalong Moderator

    Yes, and edfardos point was understood. :)

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