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Bullet Crimp

 Crimping Jacketed Rifle Bullets



Crimping of Jacketed Rifle Bullets

A frequent question on the reloading boards is "What is the proper way to crimp a jacketed rifle bullet"?

 Without getting into whether to crimp or not to crimp or when to crimp and when to not crimp, let's just assume that decision has been made and we are going to crimp. The only question remaining is "How"?

"Let's see how the big boys do it."

Our first example will be the Remington .223 55gr soft point.

Chapter 1 ( Commercial .223 Remington)

Case weight 92.2gr
Bullet Wt 55.0gr
Bullet style soft point
Powder 26.5 gr ball
Bullet:
Diameter shank .2241 - .2243
Cannelure .2215 - .2216
Nose .2225 - .2227

 

Photo instructions:  Expand images with the control key plus the mouse wheel or maximize them by click on them. They will open in a new window at the maximum resolution. Control + Wheel Forward zooms in. Control + Wheel back zooms out.

 

 

This close-up shows the mouth of the cartridge case crimped into the crimping groove, cannelure, of the bullet. The question is how much is enough and how much is too much. Notice the crimp on the outside of the cartridge mouth. It looks like the mouth of the case was squeezed in or compressed into the bullet.

 Jacketed Bullet Crimp
Left: Dog Town 55gr .224 Spitzer. ( Midway USA house brand )
Right: Remington factory loaded .223 55 gr soft point removed from the featured cartridge.
.223 bullet cannelure groove 
Here is a closer look. A groove was cut so you could see exactly what is going on in that bullet cannelure groove.    
 Here is a close-up of the inside of the mouth of the cartridge case. That crimp ring is really small.  
An extreme close-up of the inside of the case mouth showing the crimp ring after the cutting tool marks have been polished away. This view shows a decisive thickening of the case neck into the area where the bullet cannelure would be when the bullet is in the case.   
   
   
   
 

Chapter 2 ( Military 5.56x45mm NATO TW 73)

 
Case weight 94.2gr
Bullet Wt 55.1gr
Bullet style fmjbt
Powder 26.5 gr ball
Bullet:
Diameter shank .2221 - .2227
Cannelure .2216 - .2222
Nose .2223 - .2227
 5.56x45mm bullet

Here is a close-up of the crimp. The most noticeable thing about this crimp is that it is virtually invisible. In fact, it appears to be, and actually is, raised instead of crimped inwards.

The crimp is very effective. It took over 50 blows with an Inertia type bullet puller to get it out. 60 hard blows to move the bullet far enough that the crimp ring was outside the mouth. Then about ten more lighter blows to completely expel it.

 
 Bullet Crimp

Here is a close-up view of the cannelure. It looks identical to the commercial version. It is compressed into the jacket material. It is rounded, not square. I am sure that is intentional because metal tends to break at square corners.

 

The bullet appears to have a bulge at the base. I am convinced this is an optical illusion.
I cannot feel it, I cannot measure it, and I cannot photograph it.

 

 Jacketed Bullet Cannelure
 

Here is the case mouth crimp with the bullet removed. The surprising thing is that it is very small. I don't know how it held on to that bullet as tightly as it did. The crimp appears to consist of a series of very small beads extending both into and out of the case mouth.

It appears they were created by compressing the mouth metal between the beads with some sort of crimping tool that works along the axis of the cartridge case instead of squeezing the mouth of the case inward.

 Rifle Cartridge Case Mouth
Here is the cutaway view. You have to look close and expand the image to see it but the case mouth does project into the cannelure.   5.56x445mm crimp
Here is a close-up of the case wall thickness at the mouth of the case.  I can see no hint of a real crimp here but there is a tiny protrusion into the cannelure groove - See arrow.  Compare this to the Commercial version directly below.  Cartridge Case Wall   
An extreme close-up of the inside of the case mouth showing the crimp ring after the cutting tool marks have been polished away. This view shows a decisive thickening of the case neck into the area where the bullet cannelure would be when the bullet is in the case.  This is the close up of the commercial .223 in chapter one above. It is reproduced here so you can compare the two crimps more easily.  
   
   
Can you rely on the cannelure ring to set your overall cartridge length?

You be the judge. 
.223 cannelure groves  
 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

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