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Bullet Setback?


TangoShooter

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I am loading 9 mm with a 124 gr round nose bullet with a taper crimp.

To check the finished rounds for quality, I did the plunk test, measured OAL and bumped one round, bullet first a few times on the table.

No changes in OAL.

If I press the round really hard with my hand on the table, the bullet sets back about 0.07 with each try.

Can't do this with factory ammunition.

Is this normal?

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I would put the round in a magazine and actually feed it into the gun a couple times. Measure before and after

And see if the OAL changes. I don't like to see them get any shorter. Also try the different head stamps you normally use.

Not all 9mm cases are the same.

You may need an undersize sizing die for more bullet to case mouth tension.

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Cheap plated bullets are pretty soft and will deform but usually only so far. If it continues to shrink the bullet is moving and I personally don't tolerate any movement. This is why I use a UDIE.

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I guess it depends just how hard you mean by "really hard" :). But if you're pressing just as hard with factory ammo and not getting setback then that doesn't sound good that you're getting setback with your reloads. .007" isn't a lot, but I personally wouldn't want any. My reloads are much harder to setback than factory ammo, but I'm using a U die.

What sizing die are you using? And what is the measurement of your crimp? I hear too much crimp can cause you to lose neck tension and allow for setback. A taper crimp doesn't prevent setback, neck tension does, so more crimp won't help prevent setback.

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Chamber and eject a half dozen times as suggested. If it holds OAL that way, don't worry about it.

Also, the measuring methods typically used (calipers, not a micrometer) held in your hands? That isn't sufficient to repeatably measure 7 thousandths accurately. A machinist would laugh at us if we tried to tell them we're doing such things.

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Thanks to all for the good suggestions!

@ Southpaw: I'm using a Hornady sizing die.

Think I found the problem on the weekend, way too much case flare.

Reduced it significantly, no more setback when chambering a few times.

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Yep! Flare as little as needed to get bullets into the case easily. Crimp just enough to remove that belling, and you'll have much more consistent ammo.

To check crimp, pull a bullet and ensure there is no more than a faint line where the case mouth closed around the bullet. I was crimping FMJs pretty aggressively with a Lee factory crimp, which resulted in issues when shooting coated bullets because I was undersizing the bullet and cutting through the coating with the case mouth. A lighter crimp turns out to work better everywhere.

I don't even use the FCD anymore - I switched back to Dillon. Over-flaring and over-crimping are mistakes almost all new reloaders make on handgun rounds.

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To check crimp, pull a bullet and ensure there is no more than a faint line where the case mouth closed around the bullet. I was crimping FMJs pretty aggressively with a Lee factory crimp, which resulted in issues when shooting coated bullets because I was undersizing the bullet and cutting through the coating with the case mouth. A lighter crimp turns out to work better everywhere.

I don't even use the FCD anymore - I switched back to Dillon. Over-flaring and over-crimping are mistakes almost all new reloaders make on handgun rounds.

Checked the crimp, looks good (the faint line you describe). Measured 0.378". Dumped the FCD a few months ago in favor of a normal Hornady taper crimp die. Gives me more consistency with v0 and the Double Alpha case gauge.

Edited by TangoShooter
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By FCD do you mean Factory Crimp Die?

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Yes commonly referred to as LEE FCD
Is this the same thing as the Lee Post Size and Crimp die?

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Never heard that terminology before but yes the FCD can be adjusted to size the loaded round and crimp.
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