Crimping with Cannelure

[Stats Shooter]

PLEASE: THIS THREAD IS NOT INTENDED TO BE A DEBATE ON THE MERITS, OR NECESSITY OF CRIMPING. Only a discussion for those who crimp certain bullets


I have been experimenting with my Lee factory crimp die on cannelured .223 bullets. I have a couple of questions for some of you with more experience then me.

1: How are yall creating a standardization for the amount of crimp on .223, or anything that you actually crimp like .45-70 or .308 for an AR-10?

2: What do you consider a Heavy, medium, or light crimp? seems pretty subjective but that's what folks report

One thing I am doing is measuring the depth of my cannelure, then crimping no more than the depth of the cannelure. Basically i measure the uncrimped neck of a case with a seated bullet, crimp it, and crimp no more than the measured depth of the cannelure.

Im calling it heavy crimp if I crimp beyond the cannelure depth, which would likely slightly deform the bullet. Medium crimp is to the approximate cannelure depth...maybe 0.006" in some cases.
And a light crimp would be just a couple thousandths deep, or up to about half the depth of the cannelure.

 

[hdwhit]

Mississippi wrote:
1: How are yall creating a standardization for the amount of crimp on .223, or anything that you actually crimp like .45-70 or .308 for an AR-10?

While I wouldn't normally crimp bullets in 223 or similar cartridges, my practice has always been that if the bullet had a cannelure, I would crimp it.

When I needed some plinking grade bullets, I bought 2,500 55 grain FMJ bullets that have a "cannelure". I put that in quotes because when I got them, I noticed that the "cannelure" looks like someone barely touched the surface of the jacket with a dressing wheel and left some vertical scratches on the bullet jacket. I would say that it is more of a "crimp here" marking than a genuine indentation in the bullet's jacket.

Since it isn't much of a cannelure, I use what I call a "light crimp" in that I have adjusted the seater to seat the bullet to where the case mouth is at the center of the cannelure and then turn the case mouth into the scratches so that there was visible deformation of the case mouth into the scratched area of the jacket but nothing more.

As far as standardization goes, once I set up my dies for a particular load, I will load a large number of cartridges using those settings and store the cartridges. I also take an exemplar cartridge and store it so that I can use it to assist me in setting the dies back up to load it in the future.

2: What do you consider a Heavy, medium, or light crimp? seems pretty subjective but that's what folks report

It is subjective. I have never taken a micrometer to my crimps to see if there is a consistently measurable difference.

The way I describe a "light" crimp is where the case mouth has just barely been visibly displaced into the cannelure.

I've never really defined a "medium" crimp, but I suppose it would be where there is noticable displacement of the case mouth into the cannelure.

And that would make a "heavy" crimp where there is substantial displacement of the case mouth into the cannelure, but not enough so as to penetrate the bullet jacket or distort the bullet or case.

 

[Unclenick]

Actually, if you examine cases after firing crimped commercial loads, you can often make out the cannelure marks at the mouth with a magnifier, so they can be pressed fairly firmly. A hard crimp produces some noticeable difference in press effort, and I think most handloaders looking for a hard crimp with a conventional die crimping shoulder just go as far as they can without starting to damage or buckle the case. In the case of the Lee Factory Crimp Die, since its collet type crimping mechanism won't buckle a case like a conventional seating die crimp shoulder can, you can keep crimping harder until accuracy deteriorates, I expect. Indeed, I would experiment with it while watching for the amount of crimp that minimizes velocity SD and simultaneously monitor group size. If the latter stays good at the minimum level of crimp that produces the lowest MV SD, then I stop there. If going further improves accuracy, go there.

The official approach is to control bullet pull. IIRC, the NATO specs for 5.56 and 7.62 are minimum pull of 45 and 60 lbs, respectively. You just load dummies for this testing (case and bullet only). You can rig the tester several ways. Since it is a useful tool, I would look at taking one of the Lee Challenger presses and mounting a strain gauge rosette made of aluminum tempco strain gauges on the thinnest vertical of that press and attaching an exciting readout to it. Omega sells all that stuff. Then you can calibrate it by balancing known weights on a die in the top. Then install a Hornady Cam-Lock bullet puller in the press, clamp it to a bullet in your test dummy and measure the pulling force on the strain gauge. You can also use the device to test seating force (it'll just give you a result with the opposite sign) to evaluate the amount of interference fit in your cases when you seat a bullet in a case sized in your die.

You can also go old school. Mount the Lee press (or any other) to a 2×4 frame that lets you set it on a bathroom scale. Don't use the press ram. Instead, clamp the bullet with the puller. Have a board with a casehead ID hole drilled in the center and slip it over the bottom of the case hanging below the Cam-Lock tool, and then slip a shell holder over the case head under the board. Zero the bathroom scale or note the current reading and then push down on the board while you watch the scale to see how high it reads when the case is pulled off the bullet.

 

[T. O'Heir]

"...for some of you with more experience thAn me..." Forget the cannelure altogether. Quit worrying about crimping too. Everything about crimping is dependant on the load used. Not the cartridge or rifle.
Hot loads may and usually do need it. Light loads do not. Nor is a crimp necessary in a semi-auto. Loads for a tube mag lever action may need a crimp, again, depending on the load.
Your manual should have all the info you need about it.

 

[Unclenick]

He's seems to be looking at setting up to do commercial reloading of tactical ammo. Some customers may want it.

 

[Stats Shooter]

The official approach is to control bullet pull. IIRC, the NATO specs for 5.56 and 7.62 are minimum pull of 45 and 60 lbs, respectively. You just load dummies for this testing (case and bullet only). You can rig the tester several ways. Since it is a useful tool, I would look at taking one of the Lee Challenger presses and mounting a strain gauge rosette made of aluminum tempco strain gauges on the thinnest vertical of that press and attaching an exciting readout to it. Omega sells all that stuff. Then you can calibrate it by balancing known weights on a die in the top. Then install a Hornady Cam-Lock bullet puller in the press, clamp it to a bullet in your test dummy and measure the pulling force on the strain gauge. You can also use the device to test seating force (it'll just give you a result with the opposite sign) to evaluate the amount of interference fit in your cases when you seat a bullet in a case sized in your die.

Yea, I think I am going to setup a rig for something like this Nick. For what I am doing, the eyeball test just isn't going to be standardized enough for me. And while I will test for accuracy, MV variation, etc...I want to be able to break everything down for cleaning and maintenance, and set it back up with as little lot to lot variation as I can get.

plus, as I test my crimp, I need a better way to gauge how much crimp I have applied than just looking at it. The bullet hold force method, assuming brass and bullet remain as constant as I can manage, should get me back to where I was. Or at least close enough. I will always recheck for accuracy, velocity, ES etc before beginning a new lot. But consistency is key

Thanks nick

 

[44 AMP]

1: How are yall creating a standardization for the amount of crimp on .223, or anything that you actually crimp like .45-70 or .308 for an AR-10?

The way I make uniform crimps is to use brass of uniform length.

The "trim to length" is a suggestion, not a rule, but it is a good suggestion. Usually 0.01" less than maximum, its rare to find a fired case shorter than that (except for .45acp )

SORT your brass, by length. IF you find any too short, separate them from the batch and use them for loads that are not crimped.

Trim ALL the brass to either the shortest length you have or the trim-to length.

Adjust your die to give the desired amount of crimp, and since they are all the same length, cimp will be the same for all of the batch.

What do you consider a Heavy, medium, or light crimp? seems pretty subjective but that's what folks report

It is somewhat subjective. Roll crimp, I consider the case mouth just barely turned into the cannelure to be a light crimp. Medium is "noticeably" turned into the cannelure, and Heavy is brass turned all the way into the cannelure, to the bottom of the groove.

Crimping past the depth of the cannelure is NOT a good idea, generally. You are deforming the bullet, and the bullet and the case "spring back" different amounts, so it is possible to actually reduce the case grip on the bullet by crimping "too hard".