9mm crimp size at case neck

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Catpop

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I notice in the manual that neck crimp size is maximum .380 . Mine are measuring .377. Plunk test is fine.
Question: Should I be shooting for .380 ? Or does it matter?
Question: Will decreasing the case depth into the seating die solve this? Or is this more a function of resizing die and boolit diameter?
Thanks again, Cat
 
Measure the case below the flare where the bullet is seated. Adjust the crimp so it just removes the bell, or a hair more.

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The maximum is just that (a maximum allowed amount for SAAMI specs) You can even go larger if the gun and bullet combo allows it to be done safely. Measure a sized piece of brass and crimp to that diameter.
 
That would be an excessive amount of crimp that would damage the bullet.

A sized case comes out of the die a lot smaller then it will be after expanding and seating the bullet.

rc
 
Just checked my own reloads, they're at .374-.375
Then checked a box of Speer Lawman 124 gr, they're also at .374-.375
 
FWIW, simple math; a .355 diameter bullet, case wall .011. Multiply the case wall x2 (you measure and two ends) .355 + (.011 x 2)= .377 any greater and you will be able to push in your bullet by hand. The shell case diameter varies based on case type so adjust there if needed. :) Not to loose and not to tight, but just right.:D
 
LeftyTSGC said:
simple math; a .355 diameter bullet, case wall .011. Multiply the case wall x2 (you measure and two ends) .355 + (.011 x 2)= .377 any greater and you will be able to push in your bullet by hand.
No.

Neck tension primarily comes from friction between resized case and the bullet, not from taper crimp. You won't be able to push the bullet in a properly resized case with .380" taper crimp. If you can push the bullet in, you have neck tension issue that requires further investigation.

I just resized a "FC" case that's been reloaded 10+ times with .011" case wall thickness with 115 gr Winchester FMJ bullet (.355") using .380" taper crimp and 1.135" OAL. I could not push the bullet in against the bench and after feeding/chambering from the magazine, OAL did not decrease to indicate good neck tension. I am using Lee carbide resizing die which resizes cases to .372" at case mouth.


Also, case walls have gotten thicker over the years where .011" was more common, these days many case walls are .012"+.

So, .355" + .012" + .012" = .379"

With jacketed/plated bullets sized .355", I use taper crimp of .376"+ but .377"-.379" will work too.

With lead bullets sized .356", I use taper crimp at .377"+ and even .380" taper crimp will fall freely in tighter KKM/Lone Wolf barrels with a "plonk". In my newer Lone Wolf barrel with quicker start of rifling/almost no leade, chamber is even tighter and .378"-.379" taper crimp is the max I can use.
 
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I set up the "crimper" to remove the bell on the shortest cases and a hair more on the longest cases. I don't care what it measures.

And as bds posted, neck tension holds the bullet in auto cases. The "crimp" isn't really intended to do anything except straighten the case mouth back out.

The .45 ACP round pictured above was a random round I picked out of an ammo bag full of loaded rounds. I measured it for a previous thread, not because I cared what the measurement was. I am not sure I have measured a 9MM round yet.
 
From what I'm reading, I'm doing it right. My finished cartridges stay within .376"-.378". Bullets are .356".
 
You know I have to jump in to any crimp thread.

So if I measure the crimp, and it measures ok, then the crimp is fine right? I'm very much paranoid that Im not crimping right, but they are measuring fine. (measuring the highest point on the case that I can)


I cant even see this mysterious "bell", naked or magnified.
 
No.

Neck tension primarily comes from friction between resized case and the bullet, not from taper crimp. You won't be able to push the bullet in a properly resized case with .380" taper crimp. If you can push the bullet in, you have neck tension issue that requires further investigation.

I just resized a "FC" case that's been reloaded 10+ times with .011" case wall thickness with 115 gr Winchester FMJ bullet (.355") using .380" taper crimp and 1.135" OAL. I could not push the bullet in against the bench and after feeding/chambering from the magazine, OAL did not decrease to indicate good neck tension. I am using Lee carbide resizing die which resizes cases to .372" at case mouth.


Also, case walls have gotten thicker over the years where .011" was more common, these days many case walls are .012"+.

So, .355" + .012" + .012" = .379"

With jacketed/plated bullets sized .355", I use taper crimp of .376"+ but .377"-.379" will work too.

With lead bullets sized .356", I use taper crimp at .377"+ and even .380" taper crimp will fall freely in tighter KKM/Lone Wolf barrels with a "plonk". In my newer Lone Wolf barrel with quicker start of rifling/almost no leade, chamber is even tighter and .378"-.379" taper crimp is the max I can use.
We are both correct, i was providing the OP an answer to show that his original measurement of .377 was fine.

And yes i understand that neck tension holds in the bullet. But physics are physics and sure if you resize your cases to .372 and subtract the wall thickness (.348) your .355 or .356 bullet will automatically have tension. But if your cases are wider than a .355 bullet plus wall thickness then there will not be any tension to secure the bullet. I was referencing to the OP when he meantioned if he should shoot for .380, if your resizing smaller than .355 then you would have to physically open your case mouth to achieve this larger size. The formula was a reference to show that his .377 was fine. FWIW.
 
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