Gap Between Bullet and Brass?

[MichaelStrick9]

I've reloaded 9mm a few times, but this time I'm noticing something that I didn't notice before. There seems to me a gap at the mouth between the brass and projectile, and it goes all the way around. I look at my loads side by side with factory stuff, and it appears as though the factory stuff is tighter. If I move my seating/crimping die any lower, then the crimp becomes too much. Not sure if this is common, something I'm doing wrong, or something that was there on my last batches but I didn't notice. If there's not enough of a seal around the bullet, could it be dangerous? I also don't bother to debur my pistol loads, so I could just be seeing the effects of that as well.

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[jonn5335]

It sounds like you might be flaring the case mouth too much. As long as the gun runs and you arent experiencing signs of overpressure or change in oal of your loaded ammo in mag after the gun has been fired you should be good.

 

[PX4WA]

Or bullet is out of spec

9mm has no crimp, are you using a lee factory crimp die?

 

[Throckmorton]

unless you trimmed ur cases,deburring is not necessary.
check the overall length,it sounds like the bullet may be set to deep.
with ur calipers,measue the outside of the round right at the case mouth,and then move down say 1/16" and measure there,They should at least measure the same,meaning that the flare has been ironed out by the crimp ring.

a picture or 2 would be reallly helpful...a good clear picture that is.

 

[Greenbug]

A couple of possibilities....

1. Too much "flare" or "bell" on case mouth.
2. Seated bullet too deep into case (past the shoulder of the bullet).
3. Not enough taper crimp applied.

Or a combination of the 3 or all of them.

 

[RVTECH]

I am on the excessive case mouth flare bandwagon. You didn't mention what brand dies you are using but any standard seating die should be tight enough to at least close the flare around the bullet but if you have too much flare and the die is backed off to keep from roll crimping, some of your cases may be a little shorter than others and they are not quite getting their flare 'ironed out' resulting is the remaining gap.

 

[Box13]

another possibility is the seating stem is set too deep and the body of the crimp die is not tapering the brass enough.You end up with a good OAL but not enough crimp on the brass...

 

[MichaelStrick9]

Thanks for the responses! I'm using Lyman dies on a Hornady 5 stage. I don't trim 9mm, as all the brass I've ever measure and used comes in just under the recommended max spec. I'm going OAL of 1.12. Seems like there are huge variances of OAL for an FMJ in 9mm, that seems to fall in the middle of most of what I see. Projectiles are X-Treme plated, brass is R-P once fired. I do not have a good enough camera to take a picture of what I'm talking about, as it a very small gap.

I will try going with a lesser bell.

 

[Box13]

Try this...screw the seating stem out a 1/4 inch so it completely clears the bullet.Then take some of the problem rounds and recrimp them,lowering the die body a little at a time,until you have a good taper crimp with no gap around the case mouth and bullet, but not so tight you deform the bullet or case mouth.Once you have the crimp correct you can lower the seating stem back to where you like it and you.I doubt it is too much bell as a good die should correctly crimp anything as long as it fits into the die body.Too much bell will just wear out your brass faster...Robin

 

[Mikej]

I was loading up some 9mm yesterday and just for the heck of it I tried to over-bell the case mouth on a shell. With my Lee expander die I can only go so far down before it bottoms out. At that point I would not consider it WAY over expanded though. I set my expander die by setting a bullet on top of a resized shell, it WILL fall off. I turn the expander in just untill a bullet will barely set in to a shell, and not fall off, and lock it there. I also tested the difference between seating the bullet .040 OVER COL and there was no gap. There was only a slight difference in the feel of the case top compared to one that was seated AND taper crimped properly.

It seems most reasonable that the OP is using 115 or 95gr round nose, or wad cutter bullets and just seating them too deep?

Mike

 

[deadshot2]

I will try going with a lesser bell.

When adjusting the "bell", just add enough to allow a bullet to sit on the case mouth by itlself. No more brass extending around the base than necessary to just clear the bullet when being pressed into the case.

As for 9mm's having "No Crimp", not totally true. Yes, they don't have a crimp like a rimmed cartridge for a revolver but the "crimp" applied to a 9mm (or any other auto-loader) is a taper crimp designed to merely press the brass back against the side of the bullet this removing the gap you described.

One other possibility is that a round nose bullet is being seated too deep. If that's the case, back off the seater adjustment so the bearing surface (flat side) ends right at the case mouth. Remember, those OAL's shown in loading manuals are just MINIMUM OAL's and you can extend them as long as the OAL isn''t so great that the round doesn't fully chamber or the bullet falls out while handling

My suggestion to anyone loading 9mm or other autoloader calibers is to invest in a Lee Factory Crimp Die. It's an inexpensive die, easy to use, and makes sure that each and every round doesn't have one of several flaws that cause stoppages while shooting.