9mm Case Bulge

32-20

32-20

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Well, I've been reloading 9mm Luger for a while now. I have constantly had bulging in the case at the base of the bullet (3/4 of the way up the cartridge - from the primer side). I've been unable to prevent this from happening and while it doesn't seem to effect the loading of the round nor the extraction, it irritates me. It makes for a less than perfect looking round. I'm loading 124gr RN Aim Projectiles (.356"). I know that others have had this issue. What I am wondering is what can a fellow do to prevent it? It more than likely has something to do with the casing of the 9x19 being slightly tapered while the bullet itself is not but I don't know for sure... I do go back and run them through a Lee Factory Crimp die in the end. Thoughts?

This is the only caliber for which I experience this problem... It irks me!




Cheers!
- Daniel
 
32-20 said:
Well, I've been reloading 9mm Luger for a while now. I have constantly had bulging in the case at the base of the bullet (3/4 of the way up the cartridge - from the primer side). I've been unable to prevent this from happening and while it doesn't seem to effect the loading of the round nor the extraction, it irritates me. It makes for a less than perfect looking round. I'm loading 124gr RN Aim Projectiles (.356"). I know that others have had this issue. What I am wondering is what can a fellow do to prevent it? It more than likely has something to do with the casing of the 9x19 being slightly tapered while the bullet itself is not but I don't know for sure... I do go back and run them through a Lee Factory Crimp die in the end. Thoughts?

This is the only caliber for which I experience this problem... It irks me!




Cheers!
- Daniel
Click to expand...

Switch to another projectile... It's your bullets that give you the buldge.
 
32-20 said:
Have you encountered this issue with these particular bullets in the past?
Click to expand...

I don't load AIM projectiles but I have the same results with .358" dia bullets in 9mm, FMJ and XTP's even a lot of the bulk plated bullets I don't have an issue with mic to .355... The buldge starts around .356/.357... It's quite common and nothing to worry about even tho they look "less then perfect".
 
what you have is totally normal , the sizing die might be a little tight &/or set for a .355 bullet , the hour glass shape means nothing if they feed & function .
 
The buldge looks to be higher up than the base of the bullet. It looks like the case mouth is running into the crimping shoulder in your seating die. Try backing off the die body (turn the seating stem in deeper to keep the same COAL).
 
kombayotch said:
The buldge looks to be higher up than the base of the bullet. It looks like the case mouth is running into the crimping shoulder in your seating die. Try backing off the die body (turn the seating stem in deeper to keep the same COAL).
Click to expand...

Bingo.
Reset the crimping function.
 
Looks like you have two issues.

The first is the muffin-hips thing caused by a bullet expanding the case half-way down. Suputin's comment is bang-on. If it chambers and fires well, ignore it.

Not 100% sure from the photo, but it looks like the second would be an overcrimp, as noted by kombayotch. The 9mm, like the .45 ACP, headspaces on the front edge of the case. Overcrimping allows the round to go too far into the chamber and can result in overpressure and inconsistent firing. The term 'taper crimp' is one I hate as people seem to think that there should be a perceptible crimp at the mouth of the case. In reality, if you have properly sized your cases, it is the slightly-too-small inside diameter of the case that holds the bullets in place. The so-called taper crimp is nothing more than removing the bell you have to put in the case mouth to allow the bullet to seat properly.

If I am misinterpreting your photo, I will fess up, but I think you need to dig out some calipers or a micrometer and measure your neck diameter. It should be, by SAAMI specs, 0.3800" or 9.652mm.
 
Sadly, the only way to remove the bulge is to rollsize your brass.

On the left a reloaded round and on the right, a PMC Bronze 9mm 124 gr.
6861325536_75470d7a6e_b.jpg
 
kombayotch said:
The buldge looks to be higher up than the base of the bullet. It looks like the case mouth is running into the crimping shoulder in your seating die. Try backing off the die body (turn the seating stem in deeper to keep the same COAL).
Click to expand...

I never investigated this. The bulge is the same before and after the Factory Crimp. I do agree the round is over crimped, however, the bulge occurs during bullet seating. I'm going to back off the seating die and see if that alters the bulge at all.

Stay tuned...
 
32-20 said:
I do agree the round is over crimped, however, the bulge occurs during bullet seating. I'm going to back off the seating die and see if that alters the bulge at all.
Click to expand...

Theres a crimp shoulder in the seating die... that is what I was saying to adjust.

bullet_seat_crimp.gif


How much did you back it off? And are you backing the die out of the press or just backing out the seating punch? You need to be back the die out of the press. Keep backing it out till it stops creating the buldge.
 
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:rolleyes:

6e95da0f.jpg


No crimp on these reloads just enough travel into the die to iron out the flare, measure your bullet diameter if it's over .356" it explains the buldge, back off your factory crimp die and insert a round then turn the stem till it stops on the case then lower the round and turn the stem in another 1/8 of a turn just so it will remoe any excess belling on the case mouth...

Happy reloading :D
 
Hotwheels81 said:

No crimp on these reloads just enough travel into the die to iron out the flare, measure your bullet diameter if it's over .356" it explains the bulge, back off your factory crimp die and insert a round then turn the stem till it stops on the case then lower the round and turn the stem in another 1/8 of a turn just so it will remove any excess belling on the case mouth...
Click to expand...

Precisely.
 
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