A really tight crimp?
I'm asking because I'm wondering. And I don't know. Not because I'm planning on doing it. I'm really interested in the forces at work.
I'm setting up my press for a run of 200 9mm
I know what the Lyman charts say. And I know I've got factory rounds with a great deal of variation. Some that mic way different than what Lyman says on the over and under side of optimal.
And as I was setting things up using plated bullets and unprimed brass to get things into spec, I started wondering.
If I really cranked down on a taper crimp, meaning the taper was smaller than the original diameter of the bullet, what would happen?
Catastrophic failure?
Nothing?
Is that different than a roll crimp into a cannallure?
Seems they would feed with greater reliability in an auto loader. So since a lot of factory has a large OD, there must be a reason for not doing it.
I'm setting up my press for a run of 200 9mm
I know what the Lyman charts say. And I know I've got factory rounds with a great deal of variation. Some that mic way different than what Lyman says on the over and under side of optimal.
And as I was setting things up using plated bullets and unprimed brass to get things into spec, I started wondering.
If I really cranked down on a taper crimp, meaning the taper was smaller than the original diameter of the bullet, what would happen?
Catastrophic failure?
Nothing?
Is that different than a roll crimp into a cannallure?
Seems they would feed with greater reliability in an auto loader. So since a lot of factory has a large OD, there must be a reason for not doing it.
0
-
Accuracy will suffer. Pressures might go really high. Roll crimp in a channelure is for rimmed cases or bottlenecked ones.
added You will be wedging the case in the front edge chamber.0 -
Talk to me about pressures.
Split barrel?
Broken ejectors?
Failure to feed?0 -
Not sure about pressure issues, but if you over crimp plated bullets I've heard that it can cause the plating to seperate from the lead. 0 -
1st off, the 9mm headspaces on the case mouth. so you would have exessive headspace = possible broken extracor (depending on the model), failure to fire, excessive pressure. 0 -
When to much taper crimp is applied, the diameter of the plated bullet may become smaller. The neck tension will become less as brass springs back more then lead.With less neck tension, bullet set back on chambering will raise pressures to a dangerous level at times. The plating is very thin and may be damaged by to much crimp. 
More photos of plated vs jacketed bullets here> http://s338.photobucket.com/user/joe1944usa/library/Plated%20VS%20Jacketed%20Bullets0 -
Lead is a dead metal, it will deform under the taper crimp reducing its diameter to what ever it is forced into being. Pressures would not change simply because the lead deforms from the force of the brass being squeezed into it.
You can only get as tight as the modulus of deformation of the softest metal will allow.
http://en.wikipedia.org/wiki/Young's_modulus0 -
You have received good advice and knowledge on pistol loading. I have tested 45 ACP with Lead /plated /jacketed reloads for many years and thousands of rounds. in both Ransom rest and Chronograph . Roll crimp is OK if all the cases are the same length. IMHO taper Crimp is the Best way if cases are different length. I also feel you must seat in one operation and crimp in a second stage for best results in accurate
ammo . The same goes as to Chronograph results as to SD etc I feel wide variances in FPS come from wide Variances in pressure. I don't have any way to measure pressure . However I don't feel you can increase pressure to a Dangerous level due to a heavy Crimp. I think it is more likely to get High pressure from too light of a crimp combined with small bullet diameter or thin walled case BRAND or combination of more that one of these conditions allowing the bullet to be pushed deeper into the case during the chambering.I had this happen to me Twice on the same lot of ammo many years ago be for I found the root case when I Pulled the bullets and found there was very little if ANY force needed to move this brand of Bullet in this brand of once fired case. [V][xx(][:(] good bullet PULL results in good groups. [^]0 -
If the case od is bullet diameter or less, either the round is held only by extractor or the case mouth will slide into the chamber throat. The first is inaccurate, not even counting the damaged.bullet. The later can easily blow up the barrel and gun.
Three have been "roll crimps" used on .45, but not enough to bring the case OD to be less then bullet diameter. This was done decades ago when taper crimps weren't common and only a slight crimp was used.0 -
Good point. The 9mm headspaces on the case mouth. quote:Originally posted by noylj
If the case od is bullet diameter or less, either the round is held only by extractor or the case mouth will slide into the chamber throat. The first is inaccurate, not even counting the damaged.bullet. The later can easily blow up the barrel and gun.
Three have been "roll crimps" used on .45, but not enough to bring the case OD to be less then bullet diameter. This was done decades ago when taper crimps weren't common and only a slight crimp was used.0 -
Thank you all for helping me to better understand.
I don't have the time and space right now to seat and then crimp, but I see the advantages.
I'm getting some deformation in the tip of my plated bullets with my current settings.
Haven't been able to keep that from happening. Not much, but a slight "smoosh" to the tip that changes the profile ever so slightly.
I'm guessing it's due to the interior profile of my seater and the crimp as we seat motion.
But they're consistently hitting my coal target.0
Please sign in to leave a comment.
Comments
10 comments