I am getting ready to crimp 9mm for the first time. I started researching this step and saw somebody suggesting that you flair to 0.383, seat the bullet, and then crimp to 0.381. 0.381 lets the round drop into the chamber but barely sticks when pulling it out. I am thinking that I should go down a little more just until the round pulls out without sticking at all. Is that a good way to judge where I should crimp down to? I don’t want to crimp down too far.
9mm Taper Crimp Question
- Thread starter Cokeman
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I have had a few that don’t feel like they crimp at all. They go into the die and I barely feel any resistance. Then when I drop them into the chamber, they drop in with a clank and drop right back out. Does that mean that I probably did not flare them enough to begin with? Do I need to apply some crimp to them, or is that good enough?
JohnMc
Member
I flare until the bullet just goes in, I don't recall the measurement, but I flare a bit more for cast bullets. I taper crimp to .380.
Do you have a case gauge? They're good to have.
Do you have a case gauge? They're good to have.
JohnMc
Member
Also are you using jacketed bullets? I ask because you said you felt that some didn't seem flared at all.
I got away with under flaring at first because of copper jackets. My first loads with plated bullets taught me the error of my ways, shavings aren't cool. I read the Lyman manual again and learned that lesson.
I got away with under flaring at first because of copper jackets. My first loads with plated bullets taught me the error of my ways, shavings aren't cool. I read the Lyman manual again and learned that lesson.
JohnMc
Member
Separate seating and crimp dies or just one? It sounds like your seating die is crimping(most will, if set that way).
.378 is OK.
I seated them earlier this week with an RCBS seating/crimping die and I am now crimping them with the seating stem taken out. I’m betting that you are correct. It probably was also crimping. I did more than one brand of brass. The ones that are already at .378 are different then the ones that I had to cramp to get them to drop in to the chamber easily.
LiveLife
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Do you use mixed range brass?
Amount of flare and crimp will be determined by the length of resized brass. And brass tend to get shorter as they are repeatedly reloaded and work hardened.
I measure sample of my resized brass for length and use shorter ones to adjust my dies as longer cases will flare more and taper crimp more.
As to taper crimp amount, since most 9mm brass average .011" thickness at case mouth, I add .022" to the diameter of bullet to return flare back flat on the bullet (And skosh more with thicker case wall brass) - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10712225
So for .355" sized bullet, I use .377" taper crimp and for .3555"-.356" sized bullets, I use .378" taper crimp.
No. I would keep taper crimp no more than .378" for 9mm rounds as fouling build up from firing could prevent full chambering of rounds, especially in tighter chamber barrels.
JohnMc
Member
I mix headstamps for plinking ammo and run into the odd few that are shorter, those don't flare as much as their taller siblings. If the bullet doesn't go in nicely, set them aside and adjust the expander die for them. Or chuck 'em.
JohnMc
Member
Good tip!measure sample of my resized brass for length and use shorter ones to adjust my dies as longer cases will flare more and taper crimp more.
I set mine like that so long ago, I forgot.
for brass of eneven lenght, I just use a sigle stage press, run each cartridge up into the crimp die - turn the crip die until it touches, then lower the ram, turn the crimp die down 1/8 turn, then raise the ram up again to just touch it into the crimp. it is very light, but you can feel it. if you run uneven lenght cases into a fixed crip die, the crimps will not be consistent at all. spin the die up a turn, put in the next cartridge to be crimped, and do it again.
LiveLife
Member
How dirty do you run your barrels before cleaning?
Do your reloads tend to run cleaner or dirtier?
If you are using cleaner burning loads with low round count per range session in more generous factory barrels, probably not.
If you are using dirtier burning loads with high round count per range session in tighter barrels and extended period between barrel cleaning, yes.
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JohnMc
Member
That's a plunk test, yes it's an OK test. Case gauges are better, or Lyman makes an ammo checker.
LiveLife
Member
Then likely no issue with fouling build up.
BTW, here's recent 9mm 115/124 gr load development done with W231/HP-38 - https://www.thehighroad.org/index.p...124-gn-bullet-load-data.875597/#post-11652985
When I seat a 9x19 bullet in a case it measures about .377-.378" below the case mouth, my crimp at the mouth measures .373-.375" this works for me.
When "crimping" 9MM adjust the taper "crimp" to just remove the bell on the shortest cases, which will remove the bell on the longer ones (All we need to do), and give a hair of inward movement of the case as well. Too much can cause issues, bulging, etc.If you do it right, the dimensions take care of them selves, I do use a set measurement, I just remove the bell or maybe a hair more.
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