9mm learning and constructive criticism

[Soundguy]

Here is my two cents.


In semi-auto pistols, 9mm headspaces off the case mouth. While some people crimp 9mm (which is fine for 9mm revolvers), I do NOT crimp 9mm for semi-auto-pistols. If you cease crimping your 9mm ammo, you will likely solve more than one of your problems.

Keep in mind that many reloading manuals group all 'bullet retention styles' as crimping.
Also remember.. crimping can be roll crimping, collet crimping, and what most people with straight or nearly straight cases see.. TAPER CRIMPING.

I have seen flame wars and arguments about this term.. 'taper crimp'.. Many say that it is just closing the mouth bell.. ok.. sure it is.. and many people that write reloading manuals, sell reloading gear, etc.. call this closing.. a crimp...

So.. saying not to crimp may actually complicate the situation.. imagine a lurker reading this and they think they can flare a case, charge it, hand set a projectile in, seat it and go... and then wonder why their cases won't chamber.... because they have not 'taper crimped' the case.. which.. as the flame warriors like to say... closes the mouth bell.

Plenty of nuances in reloading that many of us grey hair people know.. that many of the younger or newer reloaders have not had the chance to experience.

I remember way back when if you wanted 8mm nambu ammo you ordered it from 2 buys who were making it in their garage.. turning cases like 38spl down ( others ) and swaging lead wire for projectiles. The good old days.

I still have an rcbs kit to convert 30 rem to 8mm nambu.. but heck.. 30 rem is rare-er than 8mm nambu now.. luckilly 6.8 spc's parent case is 30 rem, and you are cutting the case down anyway.. so I can make nambu brass out of 6.8 spc, and then inside neck turn it.

[JonB_in_Glencoe]

Keep in mind that many reloading manuals group all 'bullet retention styles' as crimping.
Also remember.. crimping can be roll crimping, collet crimping, and what most people with straight or nearly straight cases see.. TAPER CRIMPING.

I have seen flame wars and arguments about this term.. 'taper crimp'.. Many say that it is just closing the mouth bell.. ok.. sure it is.. and many people that write reloading manuals, sell reloading gear, etc.. call this closing.. a crimp...

SNIP>>>

Point taken.

I don't recall reading a manual defining crimping as all 'bullet retention styles' ...But I haven't read them all, so I find no reason to question you on that.

To me, crimping is crimping the case mouth into the boolit.
While I de-flare the case mouth on 9mm cast boolit ammo for semi-auto guns, I won't crimp 'em

[JonB_in_Glencoe]

Keep in mind that many reloading manuals group all 'bullet retention styles' as crimping.

SNIP>>>

I have an afterthought, is case neck tension considered a crimp ?

[Soundguy]

Yes.. That's my point.. That's why I said bullet retention. A taper crimp = removing mouth flare.... And that is the case neck tension that retains the projectile on cases that headspace on the mouth.

That was my point.. Some manuals call that a crimp... Even though it's not a roll crimp where you are bending the neck into a cannelure. Similarly a collet style crimp presses the case neck in, but doesn't fold it in... It's still parallel to the projectile.. The FCD in effect just increases the neck tension by swaging the brass.

So yeah... Taper crimp on a 9mm is closing the mouth bell.

It's a big arguing point over semantics on some sites..

[JCSC]

Yes.. That's my point.. That's why I said bullet retention. A taper crimp = removing mouth flare.... And that is the case neck tension that retains the projectile on cases that headspace on the mouth.

That was my point.. Some manuals call that a crimp... Even though it's not a roll crimp where you are bending the neck into a cannelure. Similarly a collet style crimp presses the case neck in, but doesn't fold it in... It's still parallel to the projectile.. The FCD in effect just increases the neck tension by swaging the brass.

So yeah... Taper crimp on a 9mm is closing the mouth bell.

It's a big arguing point over semantics on some sites..

This would be my definition of a crimp in 9mm as well. Removing the flare that you had previously added.


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[David2011]

The SAAMI spec on the taper crimp at the mouth is 0.3799” (9.65mm) or .380” for us mere mortals. I prefer to measure a hair’s breadth (technical term) back from the mouth to be sure I’m not measuring on top of a burr on the mouth. If your taper crimp measures the same, you’re good. Over crimping reduces the boolit diameter and if done vigorously enough, can cause headspacing issues along with the other accuracy and leading problems of undersized boolits.

[sigep1764]

I set my taper crimp a bit different. I take 10 cases and measure the case wall thickness with my caliper. I average this thickness, double it to include both sides and add it to the .358 that I size to. I then seat a boolit and gradually turn the taper crimp die down until the cases with seated boolits meet this measurement. Then just to be sure, I pull the boolits and measure them to ensure they were not sized down. They must remain in the .3575 to .358 size range.

[ioon44]

One thing I do for my 9 mm, is backing the sizing die 1 turn (.080") off the shell holder so it doesn't size the mouth as much.
This way the brass doesn't swag the bullet as much and I taper crimp just enough to remove the bell.

The barrel on my Walther PPQ SF measures .357" so I size to .3595". I mostly shoot an Accurate 140Z bullet from 12 BHN range scrap with Hi-Tek coating, extremely accurate and no leading. This load will not work in all of my 9mm's, always plunk test.
Bullet fit to the barrel is king.

[gwpercle]

I Taper Crimp ... measure nothing ... Press the boolit nose into the edge of the loading bench .

If it holds tight ...Good To Go .

If the boolit slips back into the case ... add more taper crimp until it don't .

Simple folks have simple ways ... sometimes simple beats complicated ...
... Seven Way's To Sunday !
Gary

[Hickok]

Just my experience with taper crimping 9mm and cast boolits, right or wrong, this is what I found.

I have mic'ed the case neck, read the specs in the manuals, run case through a Wilson Max. case gauge, and used a taper crimp die.

Through trial and error, I find that if I expand and flair the 9mm case with the Lee expander die/Noe M-type expander plugs, I can seat my cast boolit, and as the slug seats, the case neck forms around the boolit, the flair/bell disappears and the loaded round is "good to go."
I have proper neck tension, the round passes "plunk test" and is ready to shoot. NO taper crimp needed.

I flair the case neck just enough to start the boolit in the case nice and straight, press the slug in with my fingers for a good friction fit. No shaving the boolit/or powder coat.

Just my way of loading 9mm with cast....works for me....others may not like my methods.

I do not taper crimp my 9mm loads any more. I "plunk-test" every round through my CZ-75b barrel. It is the tightest chambered of all my 9mm pistols. If it fits the CZ chamber, it works in my Glocks, and Sigs.

Mass production of 9mm on a progressive press may be different,...I use my old RCBS press, and load one at a time.