Crimping of Copper Bullets

[Vitaly]

Recently I have started to use copper-plated bullets for my .45 loads. In one of the threads I have read that it’s not desirable to put a crimp on copper bullets (as was pointed in B. Enos reloading video). I haven’t watched the video myself, hence the question: “Why not”?

Help is very appreciated!

[Nik Habicht]

Physics majors feel free to correct me here..... As I understand it, bullets are balanced to fly in a more or less straight line when spun through the barrel.  When you put a crimp into the bullet, you may damage this balance and the bullet may tumble on the way to the target.  When I was shooting plated bullets last year, I used the same crimp I had used for copper jacketed bullets.  My plated loads tumbled.  I was advised to pull a bullet and look for an indentation in the circumference.  Sure enough, it was there.  When I loosened the crimp so that the line disappeared, my tumbling problems went away also.  Good Luck!

[EricW]

Nik,

U R correct.  

[Physics 102 Lab Mode ON]

Where you really get into tumbling issues is with objects that are more "square" (length is close to the diameter).  A small deviation can whack out the moments of intertia and cause the object to tumble off axis.  For a very cool demonstration of how an object kind of "seeks" to tumble around it's major axis, get a medium-sized hardback book, rubber band it shut, then try to spin it around its short axis.  It won't.  It does a flip every time.  If you let it do a full turn, the spine will swap sides.  This isn't an exact analogy for the bullet, but I think it's fairly close.  

I don't have any experience with tumbling bullets.  I've lived a charmed life so far.  

E

[BrianH]

The thing I noticed with this years ago was the lead underneath the plating crushing.  The plating is thin and the lead is soft, so you don't need the same crimp that you put on a FMJ.

I just back the taper crimp out and load a round, measure it, press the nose against the bench and give it hell....then measure it again.  If it doesn't slip, you have enough crimp.  I don't think amount of crimp has anything to do with anything else, functioning or otherwise (but too much screws up everthing.....)

[gm iprod]

Too much crimp on a soft projectile will usually damage the base of the bullet as it pulls itself fro m the case. This is what causes the tumbling. Not the actuall damage to the side of the projectile. If the damage was the problem then cannelured projectiles would not shoot.

Anything, even a hairline mark, on the last part of a projectile to touch the rifling, will cause problems of major significance.

Try filing the nose of usually accurate ammo and it will degrade slightly. File the base of a bunch of those projectiles and load them. See what happens.

Have fun.

[Vitaly]

Thanks much!

I will try to load plated bullets with suggested minimum crimp.

On the same subject, will "not enough" crimp affect reliable feeding of lead SWC bullets? Will the same rules of crimping apply to lead? Meaning will too much crimp affect trajectory/accuracy of lead bullets? That's 3 questions...

[BSeevers]

I load creating a distinct line around the bullet that I check after pulling rounds. I started this years ago after discovering a light crimp usually means a malfunction later.

Yesterday in practice I fired a 6 shot, 25 yard group fast, maybe .75-1.0 sec a shot using the first bullet hole as a reference. I do this to make sure the sight and gun are ok. The group was appx 2.5 inches using a paster as a guide.  My other accuracy test is one shot on a paster at 15 yards, offhand.

Could I get better accuracy with a light crimp. I am positive. But in IPSC reliability is a bigger concern to me.

If the bullet "caves" into the case on feeding it will jam. Most people check for this by measuring the round, pushing the loaded round into the bench, and measuring it again. If it doesn't change you are there. Works for me also.

I have found lead needs a different crimp adjustment but I still leave a mark as I said before, although I quit shooting lead in 96, I think.

[boomer]

PRESSURES REACH HIGH ON A CRIMPED  COPPERJACKET

COULD CAUSE YOU SOME PROBLEMS

[Patrick Sweeney]

I you find you have accuracy problems related to crimp, you should do a test series.  Use a dial caliper to measure the height of your crimp die above the press.  Also mark it with a felt tip marker.  Back the crimp die out an eighth of a turn and load ten rounds.  Back out and repeat.  (Of course keep the loads separated.

Record the settings and loads.  Shoot for accuracy.  Use the tightest crimp that gives good accuracy.

[swagerman]

Dear Reloader, nothing wrong will hapen to your bullets if you crimp them (tapper crimp them) just a bit. All of the exceses are bad. Try with a little practice which crimp not only feeds well on your gun. If you give to your reloads a very heavy and powerfull crimp, youll notice that (maybe) the copper skin that is arrownd the lead core, my crack. This you will see it either when you disassemble the reload to look the track left by the brass over the bullet, but also in your barrel, when youll find insted of fouling, little pieces of copper skin.

So, the best way to see it is by experimentation, but be carefull. Do not exceed the manufacturers presures.

Notice that you are reloading a calliber with quite poor pressures that can shoot even lead bullets with out any problem.

Good reload, Swagerman

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