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Crimp or Not to Crimp? Advise

688 views 14 replies 5 participants last post by  mm32357 
#1 ·
Cartridge 9mm Win Mag
RCBS 3 die 9mm Win Mag dies ( seater die only!)
Bullet: Precision Delta 115 FMJ RN
Case: Winchester Virgin
Taper Crimp Die: Dillon standard 9mm
Taper Crimp Target: .001 - .002

Problem: for the first time ever I was able to push the bullet down about 10-15/1,000! I pulled the bullets and they had a slight ring around the base - obviously too much crimp but it was no more than .002. So I resized and loaded another round to see if I could push the bullet down. I was not able! I've crimped every round I've ever loaded.

If these non-crimped rounds pass the kerplunk test should I start over with the crimp die or hit the range?
 
#2 ·
It seems like you have marginal neck tension. My thought process would be.

A) back off the crimp slightly. If that resolves the issue, great. If not proceed to B and C.

B) measure bullet diameter
C) measure the diameter of the shank of the exander.

Hopefully B minus C >= 0.002"

If not then the exander is opening a neck interior diameter that is too large to give adequate neck tension for that bullet diameter. As you know, taper crimping does not create neck tension.

Two ways to fix this. Depending on the dimensions of B or C.
 
#3 ·
Are you belling the case mouth? If so, you have to at least remove that. If you are not belling, just chamfering, then you can probably get by not taper crimping.
 
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#4 ·
May be a few ways to get there, but I like/need a bullet to stay in position with a semi-auto.

We’ve heard the pros & detractors, but I have a fair number of Lee FCD’s around. I like that one can easily vary the crimp from hardly any to firm, easily. Though we want consistent case length, it’s not as critical for crimping with the Lee.

Since your round appears the same as the common 9mm, just longer, a regular 9mm FCD should work, if you decide to go that route.

Just saying, don’t want that bullet moving around in the case.
 
#8 ·
The issue is that no matter what type of taper crimp die, be it a regular TC die or a Carbide Factory Crimp Die, a taper crimp die cannot rectify insufficient neck tension. But it might be counterproductive if overdone.

Unless you are describing the collet Factory Crimp die, there is zero difference in the crimping function of a CFCD. It is the post sizing ring and finger adjustment knob that distinguishes that die functionally.
 
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#5 ·
We all agree on zero bullet movement. After posting I decided to re-adjust the crimp die. Then I remembered that it was set up previously for a 147 grain. After adjusting it for a 115 grain bullet I was not able to move the bullet! Thanks to all.
 
#11 ·
From my experience if you can't see or feel any "flair" after seating a 9mm then skip crimping. I've played around with very minimal flair and no crimp and more flair and a tiny crimp, but I think the end result you want is that the expansion of the bullet in the case about equals the flair. Just my experience with cartridges that cycle perfectly. YMMV....
 
#12 ·
Not sure what you are saying in your last sentence?? It really doesnt matter how mucg flate you have the taper crimp removes it all. What does matter is the dia of the expander.
 
#13 ·
I was just saying if you have minimal flair; just enough to allow seating, then because the bullet expands the case a little it may be that there isn't much of any flair left so crimping might not be needed. I've done no crimp given this with no issues. Also, I wonder, if you do minimal flair and don't have to crimp much, your brass might last longer. Any comment on that?
 
#14 ·
This is true. With RCBS M expanders, my ammo will gauge without any crimp since the flair is so minimal. I do give a touch of crimp anyway to ensure slick feeding.
 
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