Taper crimp for the new 9mm handloader

[TKCastle]

Setup 9mm dies last night for the first time, read instructions and everything went smoothed. Consulted the Lyman manual for 9mm, got the COAL to the recommended length.

When it came time to get the taper crimp the RCBS instruction says to crimp to -.002 less then the dimension measured right below the mouth where the bullet is seated, easy, and I did.

When i load the round into the gun from the mag, eject it and measure COAL I notice the bullet is getting pushed back between .001 - .002.

1. Do I not worry about this since the the round is going to have a mid range powder charge and having the bullet be pushed back .001/.002 is minimal?

2. Do I add more crimp and continue to test load and measure COAL until the bullet shows no push back?

3. When is too much crimp too much?

Please note these test rounds are un-primed with no powder charge.

Thank You.

[jericho89]

9mm used neck tension, and you need enough to keep the bullet from setting back into the case when it is loaded. I would recommend adding a little more tension to the case to prevent movement. I have seen 9mm in a revolver with not enough neck tension that the bullets move when fired and either jam the wheel or cause a hazardous situation.

[LeadFarmer74]

1. That is very minimal movement. Just make sure it doesn't get set back more or get worse.
2. That wouldn't be a bad idea but it's up to you.
3. Too much crimp would result in higher pressure/poor accuracy. Accuracy will degrade in plated bullets if the crimp smashes the plating to much.

Sounds like you are headed in the right direction.

[Malthusian]

I agree with jerico89

You did not mention your overall length

I load to 1.144 with 124gr bullets

Besides neck tension you might be a little long

I would get a case gauge. I used to check every single round in a case gauge, now I do a random sampling. Not an expert, but I have loaded over 30K of 9mm

[TKCastle]

Loading X-treme 115 RN plated bullets to 1.169 COAL according to the layman manual.

['ol shooter]

Buy a case gauge, crimp until you just get the bell out and it drops into the gauge. Don't squeeze the bullet, it will only loosen it, learned that one.

[rg1]

The 1.169" is a maximum length for 9MM. It's much too long for a 115 grain round nose. OAL from 1.100 to 1.130" is most often used for 115 Round nosed bullets. Some seat out to 1.140" but that's long. You will have much better bullet tension seated deeper into the case.

[pacrat]

As stated above, don't overcrimp.

Check the dimensional diameter of your expander. It should measure one to two thousandths less than the bullets you use.

If your expander is .355" and so are your bullets. You don't have the required neck tension.

When i load the round into the gun from the mag, eject it and measure COAL I notice the bullet is getting pushed back between .001 - .002.

For perspective. That is 1/4 to 1/2 the thickness of an average human hair.

JM2c

[Bill Steele]

As stated many times above, the taper crimp is meant to take the belling in the case out, nothing more. Just taper crimp until the case mouth is straight, any more and you are removing neck tension, not adding it.

Brass has more spring than lead, when you press the case into the bullet with the taper crimp die, when you release that pressure the case mouth springs back more than the bullet springs back.

Your caliper likely is a +/- .001 instrument, so to say your OAL changed by .001-.002", it might have, or it might not. Just where your blade crosses the meplat of the bullet can result in a few thousandths difference in your measurement.

In any case, a few thousandths OAL isn't going to change pressures in a measurable way.

[Gringo Bandito]

if you are on facebook, hop on over to dillons page for the post info below.

One of the things I often hear people talk about at the range is crimp. How much? How little? How do you know? Well for those using a taper crimp, and pretty much all semi auto cartridges are going to fall into this camp, the math isn't that hard. Get your dial calipers out, you die hard/perfectionists can grab your micrometers instead, and measure your bullet diameter and the case wall thickness of your empty brass. With those two numbers use this formula:

bullet diameter + case wall thickness times two - .004.

So for my 9mm reloads I'm looking at:

.355 + .010(2) - .004 = .371

(eta) I do want to add that the .004 is the amount of crimp we are applying and you can adjust that to .000 if you want no crimp, just a straightened out cartridge, or .001 if you just want a very light crimp. Some of our technicians report that plated bullets are prone to fail if they go beyond a very light crimp.

Then it's just a matter of following the setup directions for the crimp die. Manuals for our presses are here: http://www.dillonprecision.com/manuals.html