Cartridge Crimping

Discussion in 'Ammo & Reloading' started by greyhawk50, Jan 18, 2012.

  1. greyhawk50

    greyhawk50 Well-Known Member

    I found this on my FB account.
    I thought it was interesting and informative. May I add that I don't have the torque arm as displayed in the video.
    I currently load only 2 center fire cartridges and they are both for 336 Marlins.
    Because of that fact, I use the Lee Case Length Trimmer System that assures exact case length every time after performing a full length case size. Then I add the primer, powder and the bullet. The bullet is seated w/o the crimp. After seating the bullet to desired OACL, a separate process is used to crimp as explained in the video. Aside from being more exact, this process avoids crimping with the bullet in motion.
    I'm curious about everyone's thoughts on this subject. What attention, if any do you give to the crimp process?
  2. Hyphenated

    Hyphenated Well-Known Member

    Crimping is one of those gray areas in reloading that everyone has an opinion about, not all of them based in fact.

    When it comes to bottle neck cartridges and bolt actions I don’t put a crimp on any of my reloads. A roll crimp actually lifts the cartridge neck off the bullet and creates an uneven tension. Cartridges without a crimp that have been sized correctly maintain an even grip and tension on the bullet. I know guys who crimp for no other reason than the factory does it, so it must be right. The factory is doing it for a whole lot of other reasons, which you don’t have to deal with as an individual loading for one specific rifle. I know some of you are asking yourself, but what about bullet push back? Cartridges in the 243 through the 30-06 category don’t recoil hard enough to have this be a big problem. I have intentionally fired my ’06 at the range with a full magazine and adding one round at a time on the top. After six or seven firings the lead tips of unfired spitzer bullets may have flattened a little, but push back is so minimal you would have to measure it with a caliper. I would guess very few of us go on a hunting trip and have cartridges exposed to that much punishment.

    Loading lever action rifles with cast bullets is a little different than the situation above, but becoming over zealous with roll crimping does more harm than good. All of my cartridges get a slight belling during preparation for loading cast bullets, so I will put a small crimp on them. This crimp is just enough to get the bell out and than a smidge past flush. The only time I might apply more crimp is if using short for caliber bullets that have less neck tension and run the risk of magazine push back. Most guys who shoot cast bullets in Marlins will tell you a snug bullet fit is necessary for accuracy. To achieve this you should be shooting bullets that are .002ths over bore, sometimes more. If you apply excessive crimp to a cast bullet you run the risk of your bullet being deformed and squeezed down fractionally at firing. Remember you are not shooting a rifle that generates 55,000psi and will blow the crimp straight. Your bullets are being affected if there is a lot of crimp left in your brass after firing.

    In conclusion, is the perfect crimp a big deal? No, not for most of us, because we are recreational shooters and minute of angle at 300 yards is not our goal, however, if you are picky about accuracy you need to pay attention to the crimp.
    Last edited: Jan 23, 2012

  3. greyhawk50

    greyhawk50 Well-Known Member

    I totally agree. I felt that the articles had a lot of good information so I shared it.
    My practice has always been to practice with the same load that I hunt with. That being a jacketed bullet at or near max load depending on accuracy.
    I currently only load 2 center-fire rifle round (30-30 & 35 rem.) and they are both 336 Marlins. For that reason, I full length size and give them a mild roll crimp.
    As for all the bolt guns that I've loaded in the past, I normally neck sized and did not apply any crimp. I've never owned anything larger than a 30-06 so push-back wasn't an issue.
    However, I have ruined more than one bottle neck case because of over crimping (normally part of the set-up process). That is when I started seating the bullet to proper length and then crimp as a separate and final step in the process. It's just me, but I see a problem with crimping while the bullet is still being seated.
    I've loaded for over 40 years and had not seen the "torque arm" before viewing this video. I thought that it was a good idea but at this season in my life, it's not worth the extra money. JMHO.