Problems with 9mm CBC brass...

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baz

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As I continue my education in reloading, I've encountered something new. I've been reloading 9mm, generally with success. But I'm having problems with CBC brass (Magtech, right?). When I seat the bullets, the case is visibly expanding where the bullet is seated, and at the base of the bullet there is a visible bulge around the case where it is obviously been pushed out by the bullet. It is not a lot, using a caliper, but I cannot imagine this is normal. It certainly doesn't happen with other 9mm brass I've reloaded.

I can run them through a Lee factory crimp die, and that gets rid of the bulge.

Should they be okay to shoot?
 
They Are Fine To Shoot !!!

As a matter of fact that ring at the base of the bullet is a good thing. It shows you that for damnsure that bullet will never recede into the case under feeding pressures.
 
Is this just a sign that CBC brass is thinner than other brands? Is it likely that it will "wear out" sooner under repeated reloading?
 
No, not necessarily...I see the same "bulge" with Winchester, Remington, PMC, and all the other brands of brass I reload. I have even seen it with some Machine gun brass. (Not recommended for reloading as I found out later as the machine gun chamber tends to be a bit bigger to insure proper function).
 
I'd be upset if I did not see this in my pistol brass, particularly that which is going to be fed through a semi-auto. It is not a sign that the brass is thin, nor does it mean your brass will wear out sooner. It is a sign that your neck tension is high, and that it would take a lot more force to push the bullet back into the case.

CDD
 
I see this often as well... I've also seen this with some commercial ammo as well. Not just 9mm either.
 
Thicker.
[...stop and think about it...]
Click to expand...
I did think about that as a possibility. But it seemed to me that if one make is thicker than another, the thickness should be reflected in the outside diameter of the cartridge, not the inside diameter. Given that -- that the inside diameter should be the same, regardless of thickness -- then it seems to me that it would be the thinner brass that would be inclined to show through the seating of the bullet, not the thicker brass.

So where did I go wrong in my reasoning?
Can somebody post some pics of this.
Click to expand...
I'm working on it. I've got to recharge the battery of my camera before I can take a picture.
 
Wrong.
The outside diameter is fixed, it has to be so as to chamber. Therefore brass thickness shows up on the I.D.

Seating a bullet in a thick case will bulge it. No problem, it is commonly known as the Coke-bottle effect and as said is a good sign your bullet will not set back against the feed ramp. I worry a lot more about the occasional thin Winchester that turns up not snug or even loose on the bullet.
 
Wrong.
The outside diameter is fixed, it has to be so as to chamber. Therefore brass thickness shows up on the I.D.
Click to expand...
Well, life is all about learning. Thanks for the information. Now it makes sense.

As for a picture, while this isn't the best quality, the glare on the cases shows pretty clearly the visible "bulge" from seating the bullets: 4tf5t84.jpg
 
Thanks for all the replies. I don't know what I would do, trying to learn this stuff on my own. The Internet, and especially class acts like THR, make all the difference in the world.
 
I noticed the ridge on cbc brass only with zero bullets. I never noticed it with Winchester bullets. They shoot fine, but they feel funky as hell going through the Lee FCD:D
 
I've seen this with the R-P, WIN, and FC I've reloaded in 9x19, both brass and nickel cases. Still got all eleven fingers! :)

The brass is fine, fire way.
 
I agree with all...:)

The brass is fine.

I use a Lee Carbide Sizing Die and a Lee Factory crimp die.

Lately, Ive been using the Winchester 115JHPFB bullet, but have used others (including the Sierra 115JHC)...

Every round that I load looks bottlenecked. As others have mentioned, that tells me that the bullet won't be pushed back into the case when the slide chambers the round. That makes me happy...:)

I even like the way that it looks...:)

If you don't want the CBC brass, please send it to me...

The only 9x19mmP brass that I've found to be way too soft (to the point that I just discard it) is the A-MERC brass. Sometimes you'll also run across a lot of Chinese brass that's too soft, too...

I've had good luck with the CBC brass...

Forrest
 
The bulge can be caused by excessive crimping. When the case mouth can not be moved inwardly due to resistance as in harder than lead alloy's tendenct to move/flow more than a jacketed projectile, the force on the case mouth is diverted down. At the base of the projectile is the first point where the case can be deflected. And the path of least resistance is out, away from the projectile. The case bulges. If using a lead alloy projcetile, an otherwise too heavy crimp will continue moving in on the alloy projectile & not be as likely to be diverted down & therefore not as likely to bulge. I think.
 
Interesting. So if I am overdoing my taper crimp die I might be causing some brass bulging in the head area, which would be a cause of the rounds not fully passing a case gauge? That is what was happening to a few of my rounds, maybe 5-10%. My question is, wouldn't this happen to most or all of the rounds if your taper crimp die setting was too aggressive?

I will try backing off on the taper crimp. I think the mouth is .380 and mine were measuring .378, so it's not like I was mashing them down horribly, just enough to get them to all drop nicely into the case gauge.

I'll have to experiment further.
 
I don't know about CBC 9x19 cases, but the CBC 9x21 ones are considerably thicker than any other brand.
9x19 and 9x21 mm case walls are often of uneven thickness, and the bulge goes always on the thinner side of the case.
 
I looked at my reloads, and it looked like my offset bulges were in remington brass. I noticed on another thread that the remington brass is one of the thinest. Would this contribute to my "problem" loading this brass?

richard
 
Life is too short to load crappy brass!

yep just a bit too much squeeze there.
Click to expand...

Well, I tried some Winchester 9mm brass tonight, and what a difference! Everything was smooth, no problems. I did back off the taper crimp a drop, so the mouths are now like .378 instead of .377 or so. Every single case gauged (I did the first 100, then random samples afterward). Also, the round to round variability in OAL appeared lower as well. They were mostly on the dot at 1.125, maybe plus or minus 0.002 or so. These rounds came out quite nicely.

So, what to do with the CBC brass? I will try lubing them first to see if that helps. I will also try them now that I have backed off the taper crimp a drop. But if I have similar problems again, I will offer up my CBC brass (probably 500 or more) in trade for something else.

Good brass is not an acquired taste.
 
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