How to improve handgun load neck tension and reduce swaging

Take 5 different brands of brass. They will spring back to 5 different diameters. Brass tries to return to its original shape. 45 acp brass tested.

This is why, for best accuracy, brass of all the same brand & lot should be used.

I put a 38 s&w plug in my 9mm die to reduce swaging of my fat .358 bullets.

I also put a 30 carbine plug in a 357 powder through die to build a 300 blackout die. You can do fun things with expander plugs.

BJung said:

I read a nice thread about 9mm accuracy loads among bullseye shooters.

Click to expand...

If you would please… where?

BJung said:

Imagine, I use to load my .357" sized bullets into a case with and inside diameter of .352"?

Click to expand...

By any chance did you disassemble any loads and see what swaging might have occurred? You’ve got me a bit curious as I have tried larger diameter (>.356) to see if there’d be a difference in group size but only saw a slight increase in V.

The best way I know of is to seat and crimp in two steps. You can seat the bullet anywhere you want without any “crimp” being possible, if you are swaging the bullet at this point, it’s not the crimp.

IMO more neck tension is lost during crimping than gained. Any reduction in the leads diameter, caused by the case being compressed around it, will reduce the “dead soft” leads diameter and the case will spring back larger. Resulting in instant loss of tension. The most tension you are going to get is the first time you stuff the larger OD into the smaller ID.

For a better understanding “Crimp”, unless one is talking about displacing a portion of the case into a cannelure, would be less confusing if everyone called it the “bell/flare removal” step.

It is also known that the Lee Factory Crimp Die (FCD) can swage lead bullet diameters to a smaller size. Thereby thwarting any plans to improve accuracy by case Sizing.
.

BJung said:

Yes, I've read that too and it seems logical. I was thinking that perhaps the Factory crimp die can be beagled (enlarged in diameter) so the finished round is just under chamber size?

Click to expand...

I had a Lee FCD for a short time (it now resides in a landfill somewhere in So. Oregon). I "beagled" it by punching out the carbide ring. Still didn't care for the die, so I tossed it....

FWIW; in all my years of reloading, I have never needed to post crimp resize any handload...

Seems like we're discussing the improper use of a die causing problems. A taper crimp die used wrong enough is obviously a swaging tool. Seems illogical to say stop swaging your bullets???? The world of expander plugs goes way beyond caliber swaps with NOE making plugs to set what interference fit you want in most calibers.

BJung said:

My friend I grew up with and I both loved the LEE FCD. He called it the "fix-it" die because any round you resized with it always chambered. We didn't know about bullet fit and how it related to accuracy at the time. From what I know now, I am concerned about the whether or not the bullet retains its dimension for the sake of accuracy after it has been seated in a case; and after seating, whether the finished round diameter will chamber. Winchester has thicker walls than Remington.. If I'm shooting a handgun with a smaller size diameter bore and bullet, then Winchester would be fine. But, with a larger bore like a BHP slugging at .356 than .355, then a thinner walled casing might be better. As for the Lee FCD, I'm going to measure the ID of the crimp die and the ID of my pistol chamber. For some guns, it will be fine. For mines, maybe not but then a custom FCD that is just under the chamber diameter would work.

Click to expand...

I'm curious what the size and spec is for the carbide ring. I would assume it's maximum Sammi spec with a negative only tolerance. With tolerance stack of oversized bullets the thickest brass and the smallest ring it could get ugly.

BJung said:

I'll measure mines later and let you know.

Click to expand...

Mine is .378

I'm trying to follow this thread, but it seems to be going in three different directions. We've got case mouth expansion, bullet seating, and flare removal and/or crimp.

In the OP, I read, "The 9mm expander measures .352.... Imagine, I use to load my .357" sized bullets into a case with and inside diameter of .352"" I don't know what this means. Where was the expander measured at 0.352"?



Expanders are usually cone-like. The amount of expansion or flare is determined by how far the brass mouth is pushed onto the tapered cone. In the OP, it also states that the 38 expander is 0.356" What does this mean? A 38 flaring mandrel might have a 0.356" nose, but it is going to open the case mouth up more than that as the mouth is pushed over the taper.

I use a Redding expander die for 357 Magnum. I took the above picture from Redding's literature. I don't like the nomenclature, but what they call the "expanding diameter" is 0.355". Because my case necks come out of the Lee carbide sizing die with an ID of 0.355", the "expanding diameter" is not really expanding the case neck. The "concentric ring" is 0.360". This is where the case mouth is opened up to accept a 0.357" bullet without swaging it or having the edge of the mouth shave it. If I adjust the expanding mandrel deeper into the die, the brass mouth will get pushed onto the "final taper." This taper opens up the mouth of the case and can flare it rather wide. I've used more of the "final taper" flare with powder-coated cast lead bullets to avoid shaving them when seating. For plated and jacketed bullets, I'm mostly using the "concentric ring." This ring opens up the first part of the mouth so the bullet will sit in it. Then I seat the bullet down into the portion of the neck that is two thou smaller than the bullet. I like two thou to avoid "crimp jump" and build up some starting pressure for good combustion. If I wanted one thou, I'd have to open up my sizing die. This expanding mandrel does not go down the full length of the neck that holds the bullet so even if the "expanding diameter" portion of this mandrel were bigger, it would not be the way to set neck tension.

Another kind of mandrel could be used to open the case neck inside diameter, but an expanding mandrel often works just to flare the mouth.

It looks like you're measuring the tip of the expanding mandrel. All that portion of the mandrel is doing is locating the brass so the flare comes onto the mouth concentrically. It's the flared cone above that which is doing anything.

For crimping a revolver/lever-gun cartridge, the Redding micro-adjustable profile crimp die is what I prefer. This post explains it with an excellent photo illustration:

https://forums.sassnet.com/index.ph...mping-problem/&do=findComment&comment=3832629

In simpler terms, the Profile Crimp Die rolls the first part of the crimp into the crimp grove. This is what holds the bullet from coming out of the case due to inertia when fired in a revolver. The second part of the profile crimp is a concave taper crimp across the crimp grove. This is what holds the bullet so that it is not pushed into the case under the pressure of the tubular magazine spring.

BJung said:

Here are my measurements. The first photo is of my three expander dies. The second is a list of Remington 9mm and .38 cases that was unfirmed, then resized using the RCBS sizing die, Lee FCD. Last I measured factory loads. I measured my revolver chamber and the point nearest the chamber was .356 and the point in the chamber nearest the extractor was .357". Sometimes I'll have chambering issues near the mouth and sometimes near the base or head. I don't know why. Not shown are my notes. I measured the inside diameter of both RP and Win cases. RP wall thickness = 0.00675" and Win wall thickness = .00775. I took sized cases and seated .38 wadcutters sized at .358". After seating and extracting them with a kinetic puller, then reseating and resizing them with the Lee FCD and extracting the bullet. The .38 OD wadcutter was remained .358! Yet, the Rem Cartridge OD with the wadcutter expanded to .3755 and the Winchester brass Cartridge OD expanded to 0.3765".

Click to expand...

I thought we were measuring fcd carbide rings. My mistake.

BJung said:

Sizing my 9mm brass gives me .001" neck tension and reduces the chance of the sized casing swaging my lead bullet.

Click to expand...

The .001" neck tension, may greatly increases possible bullet set back on chambering? More so with mixed range brass?

My 9mm Luger RCBS expander could be .354" for my cast at .3562" maybe?

I would try these expanders, if i thought i had a problem. https://noebulletmolds.com/site/product-category/expanders/

BJung said:

AJC1. I measured the inside hole diameter of my Lee FC die using a small hole gauge and a micrometer

Click to expand...

I missed the measurement. I used my caliper because that's what I have here, a good or best would be a pin, but those are at my dad's. Checking the Sammi spec my fcd is .001 below max meaning that it probably uses that margin for springback. I have a tube mic for measuring necks but I haven't measured brass yet. I may do that next week while the kids are back at school.

Ok, you guys got me curious. Redding Dual ring sizing die. Lyman M-die. .357 mag case.

Why not 9mm as the OP described? As 243Win said, If he is only getting 1 or 2 thousands interference fit he will have set back and his next post will be " Why did my gun blow up?"
So, with .357mag ABLP press, Redding Dual Ring sizing die which sizes the neck to same dia as my RCBS carbide die does, and Lyman M-die which doesn't change the resized dia of the case, only puts a step in it. I will check to see if I loose any dia with the normal sized seating stems.

This about whether an untouched sizing stem that makes an interference fit of .0055" will swage down a soft lead bullet.
I don't have any truly swaged bullets like Hornady sells that is dead soft, only plated and my WW bullets that I can mark with my thumb nail.

Case as fired - .378" outside of mouth
Resized with Dual ring - .373 outside of mouth
- .3525 inside of mouth

Flared with m-die first step of M-die .3545" second step is bullet starting step= .3600" then tapered flare.

Bullet is plated DEWC 158 gr @.358" dia.
I flared to just enough to get the bullet to stick in the mouth of the case.

Seated to the depth that Lyman seating die was set at. Length was 1.4475 which was just shy of the upper cannular.
Checked neck tension, 44 lbs. Good for normal loads, is more than fine and only light taper crimp.
Wanted to mark the bullet so I knew which end was in the case after I knocked it out.


Knocked apart with RCBS Kinetic hammer. Diameter of bullet was still .3580" No swaging.
I don't see the need to mess with your resizing stems. Plated bullets have really soft cores so I doubt that your lead bullets will be any different.

In fact I will repeat this test with one of my LSWCs that I cast myself to see what the result are with it.
horizontal mark above crimp grove is my thumbnail. Tumble lubed and sized to .358" base up.

Resized case is same .373" outside, .3525" inside.
Flared with M-die is same as above. .373 inside, .3525" outside, with step to start bullet. Step = .360"

Seated to top crimp groove with no crimp at all. This is about neck tension. Got 60Lbs of neck tension.
Alox probably has something to do with that. I get 60lbs with coated lead bullets also.
Knocked out with RCBS Kinetic hammer.
Size= base down. .358"

Again, no swaging of WW lead bullet. This is with a case resized to .3545" so again, no need to mess with the sizing profile or dia because of a fear of swaging a bullet to a smaller dia.

I don't have a factory crimp die to see what it will do to a soft lead bullet. I don't want to buy one because I never needed one. I could give it away in the "pass it forward" thread though.
I may have to try to barrow one around here, but reloaders around here are few and far between.

BJung said:

...One reloader on the thread mentioned that he would change the expander in the 9mm for the .38 expander. That would be a difference between expanding a case for a bullet measuring .355" to .357". And so, I thought, "hey, my cast 9mm bullet is swaged to .357!". That's the OP.

Click to expand...

Ok, but the expander does not size the case neck. It only opens the case mouth. The 38 expander will not size the case neck for a bullet measuring .357". It just doesn't do that. The only thing it does is flare the case mouth. If you want to flare the mouth of 9mm case more, you don't need an expander for a larger cartridge like 38, just push the flaring cone of the 9mm expander farther down onto the mouth and it will open it up wider and wider.

Expander dies are not mandrel dies like Sinclair, KMS or LE Wilson that are used to open the case neck to a certain inside diameter.