Weird Look on case after reloading 9mm

[gsewell]

I am reloading 9mm rounds on a Dillon XL650 press with 115Gr. FMJ bullets from Montana Gold. I have measured the bullets and they are .355 inches at the base. After resizing in stage 1 of the press and loading and seating the bullet, if you look at the finished round the case is smaller in diameter near the center and the bullet makes a clear mark from the top of the case to the bottom of the bullet inside the case. Now it is not much, but you can see it. The measurements are:

Top of case .376
Center of case .374
Head .386

I get the same look with once fired and new brass. I have shot over 200 rounds with no issues, so should I worry?

Thanks, Gary

[312shooter]

If I'm reading your description correctly you can see the "imprint" of the bullet in the finished round, bulging out - this is normal. You can reduce this effect quite a bit by tweaking the case mouth expantion, also using a Lee factory crimp die. I believe the cause has something to do with crimping with the seating die simultaneously, mine nearly disappeared the day I started seperating seating and crimping. Stay tuned for one of our seniors to chime in on this one.

[Hammerslagger]

Better reloading manuals like Speer and Lee have a dimensioned drawing of each cartridge that shows industry max and min dimensions at various important points on a cartridge case.

I do not have a loading manual at hand. If your ammo falls within the dimensional drawing envelope (especially at the case mouth (or neck in a bottleneck cartridge and OAL) then you have no deviation.

You might want to revisit one of the threads here that you started here about powder, and read my recent post about powder, seating depth, and pressures based on a 1981 letter by a Hercules (now Alliant) executive engineer..

Best wishes.

The 0.002" that you seem to be describing shows that the case is gripping the bullet tightly, and that it is unlikely to get seated deeper as it is chambered by an auto-loading pistol, with potentially destructive results when fired.

[LDBennett]

gsewell:

When I started reloading with friends nearly 50 years ago sizing dies (non-carbide at that point) for pistol rounds were set up to size the case so that only the crimp held the bullets into the case. It was not uncommon to pick up a 38 Special case and be able to rotate the bullet in the case. Over time and experience the reloading industry learned the value of case tension on the bullet and redesigned sizing dies to grip the bullet much tighter.

The result in 9 mm reloads (and other calibers too) is that you can see the bullet through the case by the necked-in portion of the case just below the bottom of the bullet. The case is sized down several thousandths smaller than the bullet so that the case neck tension will securely hold the bullet in the case. The taper crimp, if done right, is not the culprit. I think what you are describing is absolutely normal.

This points out the necessity of belling the mouth of the case correctly with the powder funnel of the Dillon press, through the correct adjustment of the powder measure height, so that the bullet is guided into the small case body. That assures the bullet doesn't collapse the case body while trying to squeeze into the case.

LDBennett

[Snakedriver]

I agree with L D Bennett, all my 9mm and 380 acp's have the condition you describe and they shoot just fine. Since the 9mm headspaces on the case mouth, roll crimps and such are not a good thing. The sizing die pulls the casing down to a couple of thousands less than the bullet dia. so it will fit nice and tight without excessive crimping being necessary. Thus the slight outline of the bullet on the outside of the case when finished.

[JLA]

the bulge you see near the case head is where the brass is thickest from the case head to the web, the bulge at the mouth end is the bullet in the case, and where it looks squished in is where the resizing die brought it back to spec. Your rounds are ok...

[medalguy]

I'll bet you are also using a carbide sizer die. That's what I do, and the case looks exactly as you described. I've probably shot somewhere around 10,000 rounds of this ammo and there's no problem at all with it. It does look a little strange, admittedly, but it chambers and shoots just fine.

[LDBennett]

Medalguy:

Carbide sizer dies were introduced many years ago and virtually all sizing dies sold today are carbide or have a titanium nitride coating (does the same thing as Carbide insert). It is not the carbide ring in the die but the dimensions the sizing dies make the cases. They get sized a significant amount smaller than the bullet and when the bullet is inserted the brass case stretches around the bullet base but not in other areas. This gives a "coke bottle" kind of shape to the case. It is all a product of increase neck tension found to be more effective at getting better accuracies.

LDBennett

[Terry_P]

I took up fly tying several years ago and started with instruction. The instructor said the fish don't care what the fly looks like. As long as your reloads chamber and go bang I wouldn't worry about it as I expect you weren't planning on publishing a picture in American Handloader.