one more question concerning "taper crimp"

[call1911]

Hi all!
I couldn't find anything here in regard to my question.
In case I should have missed it, please be patient with an old man.

Right now it's about 9mm Para ammo but it would be also a matter for other straight wall pistol cartridges.

Imagine the following - you prep a cartridge the usual way.
You
1) expand the case for a bullet
2) fill the case and
3) seat the bullet
Now usually the doctrinal opinion is that you
4) apply just the right amount of taper crimp to remove the belling of the case.

But what if I do NOT taper crimp and the cartridge nevertheless fits in my case gauge easily and also passes the plunk test?

What could be the necessity of a taper crimp?
Why would I add this step?
My knowledge: Bullet tension comes from the straight part inside the case and not the taper crimp.
If I use FMJ bullets there is not much danger to "strangle" the bullet but with a plated bullet this happens easily when applying a taper crimp.

So it seems there can be done much wrong for what purpose?

Or: if I expand so little that the cartridge passes the plunkt test - is the case too little expanded?

Curious about your opinion/knowledge!

Bye!

 

[Cemetery21]

I do the same for 9mm jacketed bullets - expand very little and seating the bullet seems to self heal the flare. I don't gauge, but they all feed/function fine in all 9mms I've had over the years.
Lead, coated, and all other straight wall calibers get the appropriate roll or taper crimp.

 

[Walkalong]

What could be the necessity of a taper crimp?

To remove belling, some longer cases may need it, even the way you are doing it, consider it a safeguard.

 

[call1911]

To remove belling, some longer cases may need it, even the way you are doing it, consider it a safeguard.

Sorry for not understanding:
Safeguard for (or against) what??

 

[Klaatu Barada Nikto]

Sorry for not understanding:
Safeguard for (or against) what??

If it fits in the case gauge and you can't push the round in at all (measure the overall length, push firmly against the side of the work bench and measure again) then you should be golden.
After all, isn't the case gauge supposed to simulate the chamber?

 

[call1911]

If it fits in the case gauge and you can't push the round in at all (measure the overall length, push firmly against the side of the work bench and measure again) then you should be golden.
After all, isn't the case gauge supposed to simulate the chamber?

But I wrote that it fits in my gauge any passes the plunk test even without crimping.
So why should I crimp art all und this circumstances?

 

[Virginia Jim]

Don’t over think it.

 

[vaalpens]

Interesting topic.

Fitting in the case gauge and passing the plunk test does not mean it will cycle reliably. You should do a full cycle and setback test and make sure you have reliability and don't have to worry about higher pressures. I wouldn't even think about not crimping in 357sig due to the already limited neck tension.

Be safe.

 

[Thomasss]

It's six of one or a half a dozen of another as the saying goes. With many light or even medium loads lack of crimping is not a problem. Crimping becomes a problem when the bullet shifts position after the preceding cartridge is fired. Bullets can come out of the case and spill powder all over the place inside the gun plus the bullet can get stuck in your barrel (and you may not realize it). Or bullets can get seated deeper in the case and spike the pressure on the next round fired. Either situation is a big no no. Crimping whether you need or not just solves those issues and you don't have to worry about it.

 

[Otto]

But what if I do NOT taper crimp and the cartridge nevertheless fits in my case gauge easily and also passes the plunk test?

Why would you not TC? Is there some benefit in not doing so?

 

[mrawesome22-250]

I've never crimped 9x19mm. If you don't over expand, like you have found, there is no need.

If the measurement at the mouth falls within SAAMI specs, and they plunk, it would be pointless.

 

[rfwobbly]

Glad to help an "old man" any time.

Right now it's about 9mm Para ammo but it would be also a matter for other straight wall pistol cartridges.

Therein lies the issue. 9x19 Luger is not a straight-walled cartridge; it's tapered. That means it's fired in a tapered chamber. That means an incorrectly built cartridge will go half-way into the chamber and stop. And because it goes half-way in you'll have no idea why. It could be numerous reasons.

Now usually the doctrinal opinion is that you
4) apply just the right amount of taper crimp to remove the belling of the case.
But what if I do NOT taper crimp and the cartridge nevertheless fits in my case gauge easily and also passes the plunk test? What could be the necessity of a taper crimp? Why would I add this step?

Here's why... You are making an assumption based in 1 or 2 cartridges that things will always go that way... even if there is variation in the next set of brass and/or bullets. You are assuming that all your production will always be exactly perfect. So let me ask ask a question... Are all your children alike ? You used the same manufacturing process didn't you ?

My knowledge: Bullet tension comes from the straight part inside the case and not the taper crimp. If I use FMJ bullets there is not much danger to "strangle" the bullet but with a plated bullet this happens easily when applying a taper crimp. So it seems there can be done much wrong for what purpose? Or: if I expand so little that the cartridge passes the plunkt test - is the case too little expanded? Curious about your opinion/knowledge!

Plated bullets usually have a generous radius on their base that helps them seat without much belling. FMJ usually have more of a sharp corner which will need some help on entry. Lead is typically a larger diameter and needs even more help on case entry. So we have 3 different types of bullets in common use, which will all need varying amounts of belling, and thus varying degrees of TC.

Hope this helps.

 

[call1911]

Why would you not TC? Is there some benefit in not doing so?

At one point I did what all my friends do and crimped my .223rem loads (for my AR15).
Although the bullets had a crimp groove I didn't crimp because

Interesting topic.

Fitting in the case gauge and passing the plunk test does not mean it will cycle reliably. You should do a full cycle and setback test and make sure you have reliability and don't have to worry about higher pressures. I wouldn't even think about not crimping in 357sig due to the already limited neck tension.

Be safe.

I would never NOT crimp my 357 mag either, but that's just another thing altogether.

 

[call1911]

Why would you not TC? Is there some benefit in not doing so?

Not quite the same but two things:
1) why do an additional step if not needed?
2) not the same but with my go-to-load in 223rem with 55gn FMJs the groups were terrible when I crimped an OK when not.
Shot 1000s and 1000s from different AR15s and I had never ever one problem with bullets that were not crimped.
So I assume it's maybe not the best for accuracy.

 

[Erief0g]

9mm i change the wording from crimp to de-flare or de-bell as that is all in doing.

44mag I roll crimp

45acp I can start using the word crimp but it's marginally different as once de- flared the neck tension is generally sufficient.

All cartridges go through the "crimp die" for uniformity and safety. Then all go case guage.

Those are my main calibers and a brief explanation.

 

[call1911]

I thank you all for your input and will spend some time thinking on it.

My first conclusion is:

1) I'll give a substantial amount of cartridges with no crimp at all a try.

2) I'll run a couple of magazines through on of my guns to see if there is any noticeable kind of change in OAL.

3) If along the test I get problems with function or bullet setback I'll stop immediately because it's obviously better to taper crimp.

4) But if everything goes as hoped for and nothing bad happens I think I stop taper crimping 9mm cartridges.

Once again - thanks a lot for your thoughts, knowledge and wisdom!
Bye

 

[forrest r]

I taper crimp all my semi-auto pistol reloads. Accuracy and consistency come into play when doing so.

 

[Blue68f100]

I would taper crimp all my 9mm rounds and simi-auto ammo just for consistency of feeding since most simi-auto brass head spaces on the mouth. You may not think you need it but brass varies so much as well as gun chambers, its just insurance for reliable feeding. Set your TC die up on the shortest piece of brass your have then the longer ones will get TC and shorter less.

 

[lordpaxman]

But what if I do NOT taper crimp and the cartridge nevertheless fits in my case gauge easily and also passes the plunk test?

You’re GTG. For that one round. I process range brass which can vary quite a bit, so my process has to account for this.

My knowledge: Bullet tension comes from the straight part inside the case and not the taper crimp.

I would call it the “narrower part” inside the case, where the sizing step reformed the brass to a smaller dimension. As pointed out, 9mm is a tapered case, something like .38 is straight case.

3) If along the test I get problems with function or bullet setback I'll stop immediately because it's obviously better to taper crimp.

If you have too much setback, more taper crimp will not help. It’s the proper sizing that sets neck tension which affects setback. If it won’t chamber properly, and it’s COL is ok, then it’s likely you need to remove a bit more of the belling. There are of course other reasons it won’t chamber but keeping this to belling and taper crimp. Good luck.

 

[rfwobbly]

You need to tell us what type of press and dies you are using. That's the key to this issue.
• If you are using a 3-die set in a single stage, then you are getting the TC applied for "free" during the seating process.
• If you are using a 4-die set in a Lee turret of multi-die progressive, then what is it costing you to allow the cartridge to pass through the 4th die on its way out of the press ?

Taper Crimp is simply an insurance step.



► Here's what will happen if one of your cartridges ends up not being "de-belled". As shown in the cartoon above, the presence of belling may not allow the cartridge to head space on the end of the chamber. This means the handgun may not be fully in battery. That is, the breech will be held slightly open. If the gun is allowed to fire, then the rear of the unsupported case will blow out, showering the user with hot metal bits at 30,000 psi. And this will all happen quicker than you can say "Oh my God, I need to go to the hospital !"

So the alternative to "No taper crimp" is "Direct pressure on the wound".

 

[Walkalong]

Yep, no amount of taper "crimp" will make up for poor neck tension, and over doing it can hurt neck tension. We want to adjust the taper crimp die to just remove the bell on the shortest cases, which will give us maybe .001 inward "crimp" of the longer cases.

"Safeguard". For that oddball long case that got belled more than others and may cause an issue feeding or fitting.

Some people don't flare 9MM when using jacketed bullets, but I do, as posted by @forrest r , for consistency, especially if you are using mixed brass where wall thickness varies so much.

I suppose if one is using a single stage, not having to run everything through one more time may be appealing, but I would still do it.

But it's your place your rules.

I never used to gauge sized 9MM brass, until one day..............things changed.

 

[CQB45ACP]

This is an exceptionally helpful conversation.

 

[rfwobbly]

I never used to gauge sized 9MM brass, until one day..............things changed.

Poop happens.

 

[call1911]

You need to tell us what type of press and dies you are using. That's the key to this issue.
• If you are using a 3-die set in a single stage, then you are getting the TC applied for "free" during the seating process.
• If you are using a 4-die set in a Lee turret of multi-die progressive, then what is it costing you to allow the cartridge to pass through the 4th die on its way out of the press ?

Taper Crimp is simply an insurance step.

View attachment 969158

► Here's what will happen if one of your cartridges ends up not being "de-belled". As shown in the cartoon above, the presence of belling may not allow the cartridge to head space on the end of the chamber. This means the handgun may not be fully in battery. That is, the breech will be held slightly open. If the gun is allowed to fire, then the rear of the unsupported case will blow out, showering the user with hot metal bits at 30,000 psi. And this will all happen quicker than you can say "Oh my God, I need to go to the hospital !"

So the alternative to "No taper crimp" is "Direct pressure on the wound".

Good point - the press I'm talking about is a Forster Co-Ax.
All competition ammo we need is made on that press.
It's range brass but every round is resized, deprimped, cleand in a drum cleaner, dried.
Next it's sorted by headstamp, then expanded and primed, powder trickled, bullet seated.
It's not that I see much gain time-wise from not crimping.
But why do it if not necessary and if it hurts accuracy.

(Our plinking stuff runs from a Dillon 650 where it sure would make no sense to remove the crimp die)

As I mentioned before I had only bad experience (accuracy) when crimping 223rem cartridges.
I know this is a whole other matter but it made me thinking about the 9mm ammo.

To your point about the "free TC" when using single-stage press and 3-die set:
I never could warm myself up to to seating and crimping in one step.
The pure thought of pushing the bullet in the case and at the same time applying the crimp? Not good.
I seat all bullets then I re-adjust seating stem /die body and apply the crimp.

So if crimping is maybe counterproductive to accuracy with 9mm, too then I'd rather not do it.
Still I see your point about weapon not going into battery and will watch VERY close how my little experiment goes.
As soon as I see anything that's going awry I'll stop and go the extra mile (yards) and crimp my cartridges.

Plan is to shoot 50:50 with and without crimp and at the same time write down the results to get an impression about accuracy.

 

[NMexJim]

If it fits in the case gauge and you can't push the round in at all (measure the overall length, push firmly against the side of the work bench and measure again) then you should be golden.
After all, isn't the case gauge supposed to simulate the chamber?

Yes, this is true, you can reload w/o a flare, (.355 works ok although you will probably get the occasional bent case mouth. ((bullets over .355 may not like that so well)) not take the flare out, or taper crimp to just take the flare out, or crimp more to whatever limits the brass will stand before buckling.

Look at the attached picture - a sized case and one that is flared. Note that if done correctly the flare actually takes up very little of the cartridge length. A cross-sectional look at a 9mm case shows how the inside of the case is tapered. Handgun bullets are usually straight shanked, so there is quite a bit of shank that entends below the flare. Add in the slight taper, and I usually can see the outline of the shank on the outside of the case. Finally, sure you don't have to take out the bell and indeed the rounds may fit into your chamber as shown. That doesn't mean they'll fit every chamber or that it won't cause you problems at some point.

I mic'ed every brand of factory-built ammo in my stash and only found 1 that was under .380, 2 at .380, several at .381, and 2 at .382.

But, in the end, it's all about how you reload and how everything comes together for you.