Solved My 9mm Bullet Base Bulge...

K

kilotanker22

New member
So, for a long time, I have seen the slight bulge left near the base of a bullet when I load 9mm Luger ammunition. They have never failed to fire or chamber so I never gave it a great deal of thought. Well, I sat down to load some defensive ammo the other night with new cases and Hornady XTP bullets, when I saw that the bulge was more pronounced than they are normally. I am using a Lee pro 4000 press, and the powder through expanding die that comes with the kit. I experimented with expansion to see if that works, but that die does not expand into the case, it only creates a belled case mouth.

I figured that the new cases might be a little undersized so I tried to run a few through the press after removing the sizer die. To my surprise, I found no bulge, or evidence of a bulge at all. The only variable that changed at this point was the removal of the sizer die. The rest of the ammunition loaded up and looks perfect. They seem to cycle better as well in both guns I fired them in this weekend. They have always cycled fine, but they feel like they chamber more smoothly.

So, it would appear that my sizer die is responsible for the diameter of the case being a bit tight and causing the bullet to have to expand the case as it is seated. For new cases, this is no problem, however I have not decided how to remedy this when I am recycling cases. Reloaded brass does not have as much bulge as the new brass, but it is still present. I am pretty sure that the reloaded brass is a little harder and not as easily sized as new cases are, that's why they display less bulge than new cases.

My question is, will I damage the carbide insert in the sizer die if I were to maybe polish the inside of it to remove some material? Damaging the surface of the carbide is a real concern of mine. Does anyone have a suggestion for a die that won't size cases so darn small? My next step is to play with the die to see if I can back it off, sizing the case a little less and remedy this issue. Like I said earlier, they still run in my pistols, but this has been bothering me for a while now. If they can do it at the factory in mass production, we, as reloaders, should be able to replicate that.
 
I would look at new dies before I decided on altering the ones I have. I have the Lee die set as well as a Hornady set. The lee seems to size a touch smaller and further down on the brass. The lee die is harder to size with than the Hornady, the Hornady is smoother.

One option would be the NOE expander system. Uses the lee universal expander paired with the NOE expander plugs. It goes into the case mouth to open the case up and set the neck tension of the seated bullet. I have used this with 9mm and 38/357 with good results.

LEE universal expander, midway $14.99 https://www.midwayusa.com/product/1011184394?pid=140461

NOE Plugs, $7.50 https://noebulletmolds.com/site/product-category/expanders/expander-plug-pistol/ I would give him a call and see what size you will need. I think its the .356 for 9mm, but I can't remember, I have several sizes.

Personally I would get the Hornady dies, it should solve the problem of the excessively sized brass and fix the problem. The NOE should get you the results you want, but wont fix the problem. Or you can try and polish your sizer die... but carbide it hard and keeping it round could be difficult. Or could could just roll with it as, so far, it has not caused any issues....
 
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I do not think I would use those. The press I am using is only a four-station press, and since I am crimping in a separate step using the Lee factory crimp die, I do not have a free space to use. I am also not really interested in adding many steps to the process for high volume cartridges. I will try a set of Hornady dies, or maybe Forster. I absolutely love the Forster dies I use for rifle cartridges.
 
I guess I could try the method you suggested and then seat and crimp in one step. I really prefer the factory crimp die though.
 
Crazy idea (but if not for crazy ideas I wouldn't have any ideas at all):

The Lee factory crimp die does a full-length resize. Are your fired cases so expended that a new bullet just falls in? If not, maybe try priming, charging, and seating without resizing, and just rely on the factory crimp die for the sizing.

Or ... maybe back way off on the resizing die so you're basically only sizing the case mouth?
 
Kilotanker22,

What you found is normal. If you look at a drawing of it, you will see the 9mm case is tapered a bit. Owing to this taper, the base of a bullet inserted deeply enough below the case mouth loses contact with the sides of the case at the heel, and without contact cannot expand the case diameter to produce the bulge you are referring to. Your new cases are formed with that taper.

A common carbide sizing die consists of a ring that is one diameter. It sizes the case straight as it passes through that single diameter, so it cannot produce the taper the factory put on that case, instead making it straight where it passed through the narrowest part of the ring. Yet it can't be much bigger, because if you make the ring bigger (done by lapping with diamond compound) it won't size the case mouth down enough to hold onto the bullet well.

The bulge is meaningless to function if it does not occur at or below where the brass starts to thicken inside the case. If it did that far enough down, the case wouldn't chamber. The head of the case is not resized, so the position of the round in the chamber is unchanged as compared to the tapered round.

If the lack of taper just bothers you, you can get a good old fashioned steel resizing die which will include the taper, but you will have to lube your cases to use one.
 
Thanks Uncle Nick, it just so happens that I have a Lee sizer die that is steel. The reason I was using the RCBS carbide die was to avoid lubing cases. I will try the Lee die and see if that changes anything.
 
I LIKE to see that constriction under the bullet, it means the round is more resistant to setback against the feed ramp. I use an undersize sizing die to get it for lightweight bullets, 115 gr 9mm or 200 gr .45s. Heavier bullets seat deeper into the case wall taper and a standard die is OK.

A common carbide sizing die consists of a ring that is one diameter. It sizes the case straight as it passes through that single diameter, so it cannot produce the taper the factory put on that case, instead making it straight where it passed through the narrowest part of the ring.
Click to expand...

Commonly said, but I remember when a carbide 9mm sizing die cost extra because of the longer tungsten carbide insert needed to size in a taper. Lee and RCBS prices are the same as for straight cases now, but Redding and Lyman are more. I will do some measuring this afternoon.
 
kilotanker22 said:
I figured that the new cases might be a little undersized so I tried to run a few through the press after removing the sizer die. To my surprise, I found no bulge, or evidence of a bulge at all. The only variable that changed at this point was the removal of the sizer die. The rest of the ammunition loaded up and looks perfect.
Click to expand...
Be careful when not sizing new brass. I had some brand new 9mm brass recently that I tried loading a couple of rounds without sizing and they looked fine to the naked eye, no bulge, gauged and plunked fine, everything looked great except... when I tried what I call the thumb pressure test (pushing the round against the work bench with my thumb as hard as I can), the bullet set back into the case without a lot of pressure. Neck tension was way low. Resizing the new brass solved that issue. Just saying.
 
The "bulge" doesn't cause any problem, if the loaded rounds run through FCD, so no reason to spend any energy to correct that.

The bulge is there for a valid reason. Perhaps it would be visually acceptable if it is symmetrical around? The Hornady seating die come with a centering insert to help the bullet go in centered.

-TL

Sent from my SM-N960U using Tapatalk
 
tangolima said:
The "bulge" doesn't cause any problem, if the loaded rounds run through FCD, so no reason to spend any energy to correct that.

The bulge is there for a valid reason. Perhaps it would be visually acceptable if it is symmetrical around? The Hornady seating die come with a centering insert to help the bullet go in centered.

-TL

Sent from my SM-N960U using Tapatalk
Click to expand...
The ring is pretty even all the way around. Some bullets leave a ring that cannot be felt with a finger, but still seen.
 
I have 9mm dies in Lee, Hornady and RCBS.
The bulge at the base is a little more apparent in the Lee dies but they call fit in my 9mm case gauge and none fail to chamber.
Sometimes we over think things a little too much.

If they pass the plunk test and chamber you’re good to go.
 
I understand that it is not really an issue. I have fired thousands of them with no trouble. This was just me trying to solve a riddle of sorts in my free time. Unclenick graciously gave me the answers I was still searching for.
 
Jim Watson said:
I LIKE to see that constriction under the bullet, it means the round is more resistant to setback against the feed ramp. I use an undersize sizing die to get it for lightweight bullets, 115 gr 9mm or 200 gr .45s. Heavier bullets seat deeper into the case wall taper and a standard die is OK.



Commonly said, but I remember when a carbide 9mm sizing die cost extra because of the longer tungsten carbide insert needed to size in a taper. Lee and RCBS prices are the same as for straight cases now, but Redding and Lyman are more. I will do some measuring this afternoon.
Click to expand...
This, and also why i use Lee u die for full power jacketed semi pistol loads.
 
I just wanted to say thanks to all who contributed to this conversation...... I found it interesting and most helpful...... my 9's have been doing this especially with Berry's bullets...maybe I'm not totally crazy after all....thanks, DW
 
One other bit of info: 45 Auto also has a tapered case but with less taper than the 9P. When I first got my Dillon Square Deal press (1990-ish) to be a dedicated 45 Auto press, I noticed these bulges were often uneven, sometimes to the point of vanishing on one side of the case altogether and being exceptionally prominent on the other. This was due to the bullets seating with some tilt, which increases soft bullet leading and reduces its accuracy. So I turned a powder drop tube for the Dillon measure with the Lyman M expansion die profile at the bottom tip. This makes a short, straight expanded portion with a ledge on which the bullet will sit upright. It causes the bullet to start straight into the case during seating. Since then, the rings have been very even all the way around. Not always perfect because you get some cases with uneven wall thickness, but it is very much more even, and I haven't seen a ring that vanishes on one side since then.

Today, if you have a Dillon, UniqeTek sells drop tubes with that profile, so you don't have to make your own. For those using standard dies, Lyman M dies are available, but they also have the Lyman Multi-expander die, a powder-through die for on-press charging that comes with inserts for every common pistol round from 32 to 45 caliber.
 
I wish someone would make a powder through expander along the lines of the NOE expander plugs that would work with the Lee powder through dies. One in 9mm, two in .357, and one in .41mag would suit me just fine. I suppose I could get the NOE’s and have them drilled out, hmmm I may have to think about this.
 
I have the RCBS carbide 9mm sizing die and haven't been getting the bulge you speak of with Extreme plated 9mm .355 dia. bullets. I am loading about a hundred right now with several different head stamps and never a noticeable bulge.
However, I have .380 RCBS carbide sizing die and I see that bulge quite frequently, evidently not all RCBS dies are created equally.
 
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