9mm case bulge

Crazy Horse said:

Quick question, has anyone run into any issues not applying crimp to 9mm ammo?

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OK, let's cover some basics.

First, most of neck tension comes from friction with case wall against bullet base further down the case neck towards the bottom of bullet base where the case wall is thicker. Here's a listing of case wall thickness .200" below case mouth - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10713822

Keep in mind that taper crimp is applied near the case mouth where the brass is thinner but this won't increase neck tension as much as friction from resized case wall further down the case neck from thicker case wall. Here's a listing of case wall thickness .100" below case mouth where taper crimp is applied - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10712225

This is why increasing the taper crimp won't increase neck tension.

And this myth busting thread tested the neck tension of various case wall thickness brass using NO TAPER CRIMP as flared case mouth was just returned flat on the bullet - https://www.thehighroad.org/index.p...neck-tension-and-bullet-setback.830072/page-4

So no, not using taper crimp is OK if you have sufficient neck tension from properly sizing the brass and using brass with thick enough case wall.

Besides, autoloading straight walled cases headspace on the chamber with case mouth and if too much taper crimp is applied, round won't headspace on the case mouth rather held by extractor.

And as many have posted, especially with plated bullets, using too much crimp will indent/cut into the plating (which may cause leading of barrel) and deform/reduce the bullet diameter and decrease neck tension that could cause bullet setback.

I have never crimped a 9x19.

After seating a bullet, the case mouth is always ~.376-.379".

When I loaded mostly jacketed 9mm, I did not crimp. With a minimal flare, it seemed like the mouth of the case fit the seated bullet just right. They fed and shot fine. I did start using the crimp feature when I started loading lead, plated and coated. I flared a little more so I set the crimp to just straighten the flare back down. I don't load hot, but I don't think a hard crimp gains anything as far as tension on the bullet - brass springs back some anyway and the bullet doesn't.

Cemetery21 said:

I don't think a hard crimp gains anything as far as tension on the bullet - brass springs back some anyway and the bullet doesn't.

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Good point on brass spring back, especially from work hardened brass that were reloaded multiple times gone through repeated stretch/resize cycles.

Crazy Horse said:

I had stopped using hitek coated bullets as I thought they were too soft.

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Consider these.

Hi-Tek coating is usually applied to harder cast bullets with 14-18 BHN which will resist case wall compression when seated in a resized case. And since Hi-Tek coated bullets are usually sized larger at .356", even greater neck tension will result.

Plated bullets (typically sized .355") use softer lead/alloy core softer down to 5 BHN and will reduce in diameter with application of taper crimp but due to brass spring back, will decrease neck tension.

So if your factory barrel is oversized at .357"+, you really don't want to reduce the bullet diameter any further which will decrease accuracy and may benefit from using larger sized bullets like .356"-.357" (Many bullet manufacturers offer different sizing of coated bullets).

To separate .380 brass from 9mm brass go to shellsorter.com

Buy the three piece baskets and the .380 plate.

As long as you don't put too much 9mm/.380 mix on the .380 plate this system works 100%. I normally wait till I have a five gallon bucket of brass to sort. Using the baskets and the plate it takes me about 45 minutes to an hour to completely sort my range brass.

It's certainly much quicker than weighing the brass to separate it.

When I loaded mostly jacketed 9mm, I did not crimp. With a minimal flare, it seemed like the mouth of the case fit the seated bullet just right. They fed and shot fine. I did start using the crimp feature when I started loading lead, plated and coated. I flared a little more so I set the crimp to just straighten the flare back down. I don't load hot, but I don't think a hard crimp gains anything as far as tension on the bullet - brass springs back some anyway and the bullet doesn't.

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That's how I load my 9mm also, with jacketed, plated or lead in 115gr or 124gr. I use a Shimpo strain gauge to test neck tension on my loaded rounds with,


I do not load 147gr grain bullets in 9mm so I have no results with them.

I have never seen where adding more taper crimp increased the neck tension on a bullet with a 9mm in lead, plated, or jacketed with 115gr or 124gr bullets.

My gauge goes to 65lbs of tension and i normally get 50lbs of tension from my RCBS resizing die, and my M-dies all day long. Anything over 35lbs is supposed to be good and I have tested some factory ammo where 35lbs is the mean average of tension. That's to low for my comfort level to defeat setback with heavy loads when reloading.

A taper crimp is a necessary evil used to straighten out the flare and preserve the case mouth for head spacing, and if used to much will either loosen the bullet and/or increase a scraping problem with lead.
That's why I set my taper crimp to minimum on the shortest case.

Now, with that said, all my 9mm brass has been shot many times and is hardening up which makes it resist keeping it new shape from being resized and neck sized, a little more of a problem. But I am still getting 50 lbs of neck tension with most all my 9mm cases.

While I'm loading on my LNL-AP if I feel anything different (lighter) than normal, I check for split cases in station one, 380 case in station one, and pull the finished round off the shell plate and check neck tension.
I have found brass that just won't hold tension any more, even though it does not look like a single thing is wrong with it.

The last ones I pitched only showed 30 lbs and neck tension so I knocked one of them apart and ran it through the press by itself and they still only had 30 lbs.
So they got culled.
If using brand new brass that is soft and supple, a heavier taper crimp may make a difference, but I cannot afford to buy new 9mm brass and would be insane to do so with all the brass that is laying around or can be bought so cheaply. And who's to say the new brass won't have some that are the same way.

This instrument costs a lot but it doesn't make mistakes. If the bullet moves any at all the hand stops moving and that's my neck tension. The hand stays in that position until I push the release and it returns to zero.

tightgroup tiger said:

I use a Shimpo strain gauge to test neck tension on my loaded rounds

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Nice!

I just use a low tech approach and measure finished rounds before and after feeding from a magazine without riding the slide.

With good neck tension rounds, I get no bullet setback which I demand for various accuracy testing/myth busting threads. I now only use particular headstamp brass that won't produce any bullet setback for my accuracy testing.

With decent neck tension rounds, I get a few thousands which is OK for range blasting ammo.

The company I worked for at one time, bought a new digital model and told me to get rid of this one so I threw it away in the cab of my truck, and hauled it away for them for free.

They were funny that way, if it didnt get used it got pitched no matter what it cost.
Talk about waste.

tightgroup tiger said:

The company I worked for bought a new digital model and told me to get rid of this one so I threw it away in the cab of my truck, and hauled it away for them for free.

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You are such a "green" reloader.