Pistol crimp question

[JustAGuy2020]

Am reloading my first batch of 9mm and have a question on removing the bell from the mouth of the case.

I only put the absolute minimum bell on each case...just enough to get the bullet started. All my cartridges fit my chamber just fine without crimp. Is it required to taper crimp the small amount of remaining bell out of the case for some reason?

Thanks

 

[rsrocket1]

No need to do it so long as you get 100% chamber and 100% feed out of the magazines into the chamber.

Then again, if you are not shaving anything off the bullet by lowering the seat/crimp die a little lower than just kissing the case so it closes the bell, why not do it? That's if your seat die also has a crimp feature.

 

[243winxb]

It helps feeding.

 

[rfwobbly]

Good question.

Taper crimp on the 9 is really important because the case itself is tapered, and thus must fit into a tapered chamber. That makes your barrel the ultimate judge of whether you have enough TC or not.

The generally accepted test is this: can you drop a finished round into the naked chamber (barrel removed from the gun) and have the cartridge (using ONLY its own weight) go all the way in? And then secondly have it fall right back out, again using ONLY its own weight. No helping, tapping, shaking allowed.

Correct taper crimp on any auto cartridge is a die adjustment that requires the finest touch. The setting you are making is in the .002" range, which is about 1/2 the diameter of a human hair. So getting it right can be tedious. Once set though, if you have good lock rings that can hold the die in that position, you should be good for life. IME taper crimp is not nearly as finicky about cartridge case length as roll crimp.

Lastly, TC is one of those settings where just enough is perfect, and more is definitely NOT better. If you are using plated or lead bullets, you do not want to leave a mark on the bullet itself.

Hope this helps!

 

[nevadabob]

rfwobbly...I appreciate your comments to the OP. But your last sentence puzzles me: "you do not want to leave a mark on the bullet (jacketed/plated)". If you crimp, you're going to leave a mark on the bullet. How does one crimp without leaving a slight score or mark on the bullet? I am new to reloading and understand the term "just enough" when it comes to crimping. I'm headed out the door but will be back later today. Thanks for any help to my question.

 

[rcmodel]

Think of taper-crimp as Not a crimp.
It should have nothing to do with crimping the bullet in place.
Case neck tension is what holds the bullet in place.

Think of it as straightening the bell and returning the case to perfect straightness on the sides.

Two factory 9mm loads (Fed & Rem) I have measured are taper-crimped to an O.D. of .376" at the edge of the case mouth.

Use your calipers to measure the crimp and Shoot for that when you adjust your seating die.

rc

 

[LiveLife]

No need to do it so long as you get 100% chamber and 100% feed out of the magazines into the chamber.

I have a question for those that do not flare the case neck.

When the spent case is resized, the inside diameter of the case is reduced smaller than the diameter of the bullet. Unless the bullet base has rounded/tapered bottom, how are you seating the bullet without crushing the case?

For me, seating FMJ bullets with flat base requires case neck flare. Even for plated bullets with "rounded" base, seating them without case neck flare will result in slight "bulging" of case which results from minute crushing of case that shortens the case and makes the outer diameter larger.

This is less obvious in factory barrels with generous chambers and the bulged cases will drop in freely with a "plonk" but in my tight chambered Lone Wolf barrels, they won't chamber fully, indicating they may not reliably feed/chamber in all pistols/barrels.

I reload for multiple pistols of my family/friends/neighbors and must ensure all of the finished rounds perform reliably in all pistols/barrels. IMO, applying case neck flare just so that the bullet base can be placed inside the flared case neck is a good reloading practice to ensure you are not crushing the case.

Think of taper-crimp as Not a crimp.
It should have nothing to do with crimping the bullet in place.
Case neck tension is what holds the bullet in place.

Think of it as straightening the bell and returning the case to perfect straightness on the sides.

+1. For me, adding .020" to the diameter of the bullet will either apply flat taper crimp or slight negative taper crimp as depending on headstamp, some case walls are thicker than .010".

 

[rfwobbly]

rfwobbly...I appreciate your comments to the OP. But your last sentence puzzles me: "you do not want to leave a mark on the bullet (jacketed/plated)". If you crimp, you're going to leave a mark on the bullet. How does one crimp without leaving a slight score or mark on the bullet? I am new to reloading and understand the term "just enough" when it comes to crimping. I'm headed out the door but will be back later today. Thanks for any help to my question.

RC said it best. It's not a crimp to restrain the bullet, it's an operation to remove the case belling (flair).



See the tiny gold ring at the case mouth? That's the TC my Lee "Taper Crimp Die" left behind. (* Not the Lee "factory crimp die". That's a different animal and a whole other story.)

As I said, it's a very ticklish adjustment for someone who hasn't worked on miniscule adjustments before. Not enough and the cartridge won't drop into the chamber. Too much and you're going to get vastly different results from different hardness bullets.

To be precise, on your softest bullets you may indeed see a slight ring, but it should not be anything you can detect with a finger nail. On your jacketed bullets, nothing. There is a "happy zone" and you can find it. Just take your time.

 

[LiveLife]

For plated bullets, Rainier Ballistics recommends we use light taper crimp and Berry's MFG says to not use tight roll crimp as if plating was cut through, plating separation can occur from lead core.

If bulging of case occurs with jacketed diameter bullets, this is one instance where Lee Factory Crimp Die (FCD) can be used to resize the outer diameter of the finished rounds to reliably feed/chamber in tight barrels; however, if using larger than jacketed diameter plated bullets like Berry's (sized between .3555"-.356") and X-Treme (i.e. 9mm comes sized .355"/.356"/.357"), post-sizing of finished rounds may reduce the diameter of the bullet but the case wall spring-back may reduce neck tension.

So, I suggest use of FCD on jacketed diameter bullets only.

 

[JustAGuy2020]

re: RSrocket's reply;

I seat and crimp in separate steps. My seating die is adjusted far enough UP that it doesn't "crimp" at all during the seating process. It's the shaving of the plating that I avoid by doing the two distinct steps.

 

[rfwobbly]

And applying the TC in the final step seems to be the optimal way to do that, especially if you have a progressive press with the die room.

 

[nevadabob]

Thanks for chiming in! I appreciate the info.

 

[gamestalker]

Since you are only using the absolute minimum of belling, just apply a minimum of crimp to close the mouth. I'm assuming you don't trim your auto loading brass, and if so, then I would recomend using the cimp die as suggested. This will eliminate inadvertant feeding issues that may present a result of not closing the mouths.

On another note, I load only jacketed bullets and don't need to bell the mouths, I only ream and chamfer to allow for proper seating.

 

[littlebob3]

rfwobbly... Many thanks for your post, it helped help me a lot.

LittleBob3