Understanding the Hornady Factory Crimp

[Hoot]

Taken from another thread...snip...

Regarding the Hornady -- this was noticed by HOOT long ago -- is there appears to be a secondary ring on the mouth of the case. It is barely perceptible and you need a magnifying glass to see it. Looks like the case mouth contacted a sharp edge (all 450B Hornady ammo I have has this) during the crimping which turns a portion of the case mouth into the bullet while leaving plenty of surface to head space on. Who knows -- maybe this is a way to compensate for varying case lengths. I can not see it after the case has been fired. HUMMM! Part of Hornady's secret loading procedures to turn out top notch ammo?

What Siringo is saying may be hard to visualize, so I made these two drawings to represent what I suppose is how it's done. They are more a concept than actual drawing as I have not been to the Hornady factory. It appears to be some variation on a roll crimp, that cleaves the edge of the mouth, driving half the wall into the bullet and leaving the other half straight to headspace on. These drawings exaggerate that effect for the sake of comprehension:

Here is the die poised to crimp


Here it the die acting upon the case mouth


I Repeat: this is strictly supposition on my behalf. The shape of the wedge may be more equilateral.

Not having heard much about factory loads experiencing drastic bullet pull from repeated seating, I must assume it is quite effective. Once the bullet pushes it's way out of the case, it closes the gap back up and what you see if you inspect a spent factory round is just a line between the inside and outside edges of the mouth.

EDIT: We need someone to contribute to the greater understanding of the group. You need to take a factory round. Starting at the case mouth, cut a slit down one side, with a Dremel wheel, long enough to shake out the powder through. Then, continue cutting down the length of both sides, stopping just before the web. Cut around one half and remove it to see what kind of lip there is and how it is driven (supposedly) into the bullet. Pictures would be a big plus. I don't have any factory rounds or you would already be looking at those pictures.

Hoot

[Siringo]

Great drawings. Instead of using the "sparky" dremel tool -- what about using a tubing cutter and cut the case in half and dump the powder out that way.

[Hoot]

Great drawings. Instead of using the "sparky" dremel tool -- what about using a tubing cutter and cut the case in half and dump the powder out that way.

You can do that, but the carborundum disks don't spark on brass, copper, or lead. You just have to control the cut speed to not generate enough heat for combustion. IE let the blade do the work, not horse it. Actually, you'd have to try on purpose to generate that kind of heat with a single cut on brass and that cut only has to be something like 1/3" to make a gap to shake the powder out of. Otherwise, try to keep the tubing cutter about midway down so as not to disturb the mouth area.

In case no one ever looked, the guide sleeve in the seating die is not already set up to do that cleave crimp. I checked so we'd not all look on slack jawed as we realized we had the solution all along. It it wasn't hardened, you could probably mod it with a lathe and some really fine cutting work to make it into a cleaver crimp, assuming that's what Hornady is doing.

Hoot

[Siringo]

OK -- understand on the cutting! You first!!!!!

[Siringo]

Hoot -- do you suppose that the "cleaver" die would be set up to sense the same amount of pressure to apply the crimp on each case? Not all the brass is the same length -- so it would have to be floating. But there would have to be a way to make the same crimp on all cases regardless of length. That is a huge factor in accuracy.

[Hoot]

Hoot -- do you suppose that the "cleaver" die would be set up to sense the same amount of pressure to apply the crimp on each case? Not all the brass is the same length -- so it would have to be floating. But there would have to be a way to make the same crimp on all cases regardless of length. That is a huge factor in accuracy.

That's a good point about length. All I could think of would be spring loading the sleeve with a spring that's powerful enough to exert the right pressure to make it happen before it reached the end of its travel. Then you just sit the die high enough to accommodate your shortest brass and the spring would compress if they were longer.

Believe me, if I had a factory round, I'd cut it in the wink of an eye. I've never put a factory load through mine. Can't justify buying a box of what I have several hundred components on hand to do myself now. That would buy me another can of powder.

Hoot

[Texas Sheepdawg]

I'll try some pictures of a factory load with a Macro lense on my DSLR. If they turn out
Good, I'll post.

[Siringo]

Hoot -- do you suppose that the "cleaver" die would be set up to sense the same amount of pressure to apply the crimp on each case? Not all the brass is the same length -- so it would have to be floating. But there would have to be a way to make the same crimp on all cases regardless of length. That is a huge factor in accuracy.

That's a good point about length. All I could think of would be spring loading the sleeve with a spring that's powerful enough to exert the right pressure to make it happen before it reached the end of its travel. Then you just sit the die high enough to accommodate your shortest brass and the spring would compress if they were longer.

Believe me, if I had a factory round, I'd cut it in the wink of an eye. I've never put a factory load through mine. Can't justify buying a box of what I have several hundred components on hand to do myself now. That would buy me another can of powder.

Hoot

I'll give you one! want to meet at the Gun Stop Tommorrow after work? I need to talk to you about something else anyway.

[wildcatter]

Hoot, might want to check-fire on cutting into a loaded round.

I once thought I could do exactly as you have described and drill a small hole into the side of a loaded 223 case. I was using copious amounts of cool water, but to no avail. I had a detonation and my fingers were used to study the case, at that exact moment. My thumb and fore finger, took the brunt of the blast.

Fair warning, but cutting into a loaded case is a bad idea, from my stand point..

..t

[Hoot]

Hoot, might want to check-fire on cutting into a loaded round.

I once thought I could do exactly as you have described and drill a small hole into the side of a loaded 223 case. I was using copious amounts of cool water, but to no avail. I had a detonation and my fingers were used to study the case, at that exact moment. My thumb and fore finger, took the brunt of the blast.

Fair warning, but cutting into a loaded case is a bad idea, from my stand point..

..t

Ouch!

Perhaps a tubing cutter would be the safer approach. Siringo, I get off at 3PM and can be at Gunstop at 3:20 if that works for you.

Not that I'm trying to shake everyone's regard for my judgment or vie for moron of the year award, but late one evening I was having trouble pulling a 7.62 Nato bullet that was sealed in with tar, using my inertial puller. I have since gotten a collet pullet, but I tried warming the bullet and neck with a heat gun. By the grace of God, I had the round also between my index finger and thumb pointing straight up and down when it went off. Stung like a SOB and I still attribute some the white hairs on my temples to that one. So, I know how it feels, both to pull such a boner and to realize that as you tunnel in too deeply on an idea, common sense sometimes gets upstaged. Double if it's after 11 PM.

Hoot