How to improve handgun load neck tension and reduce swaging

[AJC1]

Modern carbide rcbs sets have two step mandrels that expand the case and give a step like the Lyman m die. If you cram it way down in the case you can trumpet the case like a lee flaring die. What you should be looking at in the rcbs line are the cowboy series designed for lead. Or you can get the cheap Lee and use the noe plugs.

 

[Mark_Mark]

I’ve learned so much from you guys.. But neck tension the most interesting concept.

Also, Noe M profile Expanders are the Bomb!

 

[BJung]

Modern carbide rcbs sets have two step mandrels that expand the case and give a step like the Lyman m die. If you cram it way down in the case you can trumpet the case like a lee flaring die. What you should be looking at in the rcbs line are the cowboy series designed for lead. Or you can get the cheap Lee and use the noe plugs.

I was suspicious about your comment and remeasured the expander plug on my 9mm carbide die. Using and outside caliper, the end measured 0.355" and nearest to the flare, the expander measured 0.356". I didn't take measurements from the expander on my .38 RCBS Carbide die.

 

[tightgroup tiger]

Modern carbide rcbs sets have two step mandrels that expand the case and give a step like the Lyman m die.

When did they start this? My RCBS 9mm die set is 10 yrs old and have no step on the expanders. I bought an M-die to use because of it.
That would be nice to not have to buy an M-die with every set of dies I buy.

 

[greyling22]

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.

Which sounds good but just isn't true. At least for me. Maybe it is because the 9mm is a tapered case and the portion of the case behind the mouth is being sized to mouth dimensions? I dunno. But my 9mm and 30 carbine both have the wasp waist look to them.

But anyway, for me, the 38 plug does expand the case, in addition to flaring the mouth. I do t remember the exact dimensions anymore, but I pulled bullets before and after switching to the plug, and I was getting case swaging before that I am not getting after. Most of my leading problems went away after making no other changes than switching from the 9mm plug to the 38sw plug.
Not saying everybody needs to do it, but for the oversized bore of my witness match, with my cast reloads, it was a game changer for me.

 

[AJC1]

When did they start this? My RCBS 9mm die set is 10 yrs old and have no step on the expanders. I bought an M-die to use because of it.
That would be nice to not have to buy an M-die with every set of dies I buy.

I don't honestly know but the gray box carbide set I have works just like my noe plugs. It's the reason I haven't bought them for pistol. I do use them on rifle.

 

[westernrover]

Which sounds good but just isn't true. At least for me. Maybe it is because the 9mm is a tapered case and the portion of the case behind the mouth is being sized to mouth dimensions? I dunno. But my 9mm and 30 carbine both have the wasp waist look to them.

But anyway, for me, the 38 plug does expand the case, in addition to flaring the mouth. I do t remember the exact dimensions anymore, but I pulled bullets before and after switching to the plug, and I was getting case swaging before that I am not getting after. Most of my leading problems went away after making no other changes than switching from the 9mm plug to the 38sw plug.
Not saying everybody needs to do it, but for the oversized bore of my witness match, with my cast reloads, it was a game changer for me.

Fair enough. The actual problem here is that your sizing die is excessively sizing the case down for your oversize bullets. If using the nose of the flaring plug on a 38 die works, it works. Often, the nose of the flaring plug will not have sufficient length to size the neck for anything but very short bullets. The other problem would be finding flaring plugs suitable for other cartridges -- suppose you wanted to expand the neck of 357 cases to .357" for a .358" bullet, what expander die would you use? I can't think of one.

The KMS expander dies come with mandrels for popular calibers -- including 35 caliber (some other mandrel sets are smallbore only). The KMS mandrels also come with bushings to allow the finished inside diameter to be set in 0.0005" increments, and they come with pin gauges to check the result. https://kmshooting.com/product/custom-standard-expand-mandrels/ (I don't know if it could be made to work with 9x19; might take modification since this is normally rifle stuff)

 

[BJung]

I don't understand how the KMS expander works. I use the RCBS expander plugs which look similar to the RCBS expanders in the carbide dies in concept. The expander plugs expand the case neck and flare the case mouth. Lee only expands the case mouth. This would be a problem for bullet casters with soft than jacketed bullets. The M-Die is the solution for some. I opted for the RCBS expander plugs. Yet, the case mouths should be expanded to atleast provide for a consistent neck tension, whether it is tight or not. Uneven case walls are the problem than then needs to be addressed unless (in case of rifle casings) the necks are all expanded with a mandrel and the necks are turned to the same thickness. I see your point that you need some tension so a bullet is forced into the case. But how many thousands of an inch is sufficent to provide this? Don't revolver reloaders add crimp to increase the tension on a bullet to assure accuracy?

 

[westernrover]

A taper crimp used on most rifle cartridges and on handgun cartridges that headspace off the case mouth is really just a flare-removal.
A roll crimp on revolver cartridges retains the bullet from being knocked forward, out of the case under inertia of recoil and potentially blocking cylinder rotation. To be effective, the bullet should have a crimp groove to roll the case mouth into. There are some alternatives like rolling the case mouth over the ogive or pressing it into the bullet to cut a groove.
Real crimps (not just flare removal) into grooves can also prevent bullets from being pushed into the case under spring pressure in a tubular magazine. Crimps can also be used in machine guns to keep bullets in the magazine, belt, or ammo can from being knocked in or out under repetitive recoil.

A crimp helps prevent problems with cartridges before they're fired, but generally does not improve accuracy when they're fired. The only scenario I can think of where they could help is with compressed loads of spherical powders that burn slowly due to a heavy coating of deterrent. A heavy crimp can add to the start pressure. The resulting pressure increase inside the case helps ensure combustion of these harder to ignite loads. This ensures more consistent combustion with these loads and therefore better accuracy compared to inconsistent ignition and higher SD's without the crimp.

As for holding the bullet in the case neck with the spring pressure resulting from the elastic deformation of the tubular brass neck and with the friction between the bullet and the brass, I don't know that much. I know that with a neck ID only one thou or less under the bullet diameter, bullets can slide in or out without much force. I can sometimes push them with my fingers. If I use closer to two thou, they grip pretty firmly. I can't tell you exactly what dimension will hold the bullet securely against finger pressure because there are other variables. Even if my sizing method and bullet diameters are perfectly consistent, there can be differences in the consistency of my annealing and the friction coefficients of the brass and bullet surfaces. Even the best methods are known to produce inconsistent results. That's why some loaders use hydraulic or electronic force gauges (ie. 21st Century or AMP) to measure the force of seating the bullet, and then they sort cartridges into groups that had similar seating force. The AMP setup provides the most data because it records and graphs the seating pressure over the whole stroke of the press. While this provides a lot of information, it's not the same as knowledge, neither is seating pressure the same as neck tension, nor neck tension "accuracy."

PS: I suppose the answer to "how much" neck tension is however much is necessary to keep the bullet from moving before we want it to; and what may be more important that having just enough and not more than necessary, is having the tension consistent among all the cartridges in a group. Group size is going to be more dependent on that than whether it's one thou or two thou.

 

[westernrover]

Earlier in the thread, you were considering whether the bullet is swaged by the neck under the force of deforming the brass. I suppose if the bullet were soft enough that it could be deformed (swaged) significantly, but conversely, if it were that soft, it would also undergo even more obturation upon firing. Surely the force of firing is greater than the force of brass deformation when seating.

What I would concern myself with is damage to the edges of the base of the bullet. This has proven to be detrimental to accuracy. Personally, I have no interest in cast lead bullets and my advice should be taken as coming from one without knowledge of loading and shooting cast.

 

[BJung]

Westernrover, thanks for the tidbits of information that's new to me. I agree, damage to the base is detrimental to accuracy. After to unflared case mouths sheered the base of my cast bullets. Neck tension has intrigued me since I forced a sizing mandrel through my 7.7x58 reloads and using 174 FMJBT bullets and the group tightened up. My thoughts about neck tension seems to be coming into full circle for handgun loads though. First, you might find an accuracy load for cartridge given a certain seating depth. But within limits, if you change the seating depth, pressure will increase or decrease. Then again, you adjust that by increasing the powder load.

 

[lordpaxman]

What I would concern myself with is damage to the edges of the base of the bullet. This has proven to be detrimental to accuracy.

I have read other articles that claim this but can you reference where it’s proven? I’m more interested in pistol loads than rifle although the accuracy detractors might be the same. I shoot various bullet types and would be interested to know if or how I could look for this.
I run a AA PTX which is an M style expander and the only neck tension test is measuring COL after successive chambering, and an unscientific thump test. I would think a consistent neck tension would provide better grouping, but wonder if there’s a “tension node”, similar to a velocity node where some amount of tension would provide good precision but the groups would be independent of the amount?

 

[Blue68f100]

I have read other articles that claim this but can you reference where it’s proven? I’m more interested in pistol loads than rifle although the accuracy detractors might be the same. I shoot various bullet types and would be interested to know if or how I could look for this.
I run a AA PTX which is an M style expander and the only neck tension test is measuring COL after successive chambering, and an unscientific thump test. I would think a consistent neck tension would provide better grouping, but wonder if there’s a “tension node”, similar to a velocity node where some amount of tension would provide good precision but the groups would be independent of the amount?

This is more pronounced in heavy Mag Revolver rounds like the 357 mag, 44 mag... These require a heavy roll crimp to hold the bullet longer, for pressure to build for a complete combustion. With straight wall simi-auto ammo, the faster power does not need this extra hold. I've always believed if you use a primer that is more powerful than needed (like SR instead of SP) the extra energy from the primer alone, moves the bullet causing the effect of longer OAL, One of these days maybe someone will run a test to see how far the primer only can drive a bullet into the barrel with no powder. And measure how far the difference is. Smaller the case more the pressure change.

I've like many others have done OAL testing when we have finished a load workup. On 9mm I saw group sizes reduce with shorter OAL by significant amount, 1/2 reduction. This happen on my BHP. The reason for the reduction was I could not eject a live round. Have not noticed that in my other guns, but really have not tested. I prefer to have my ammo fit all of my guns without having to keep things separated.

 

[AJC1]

I have read other articles that claim this but can you reference where it’s proven? I’m more interested in pistol loads than rifle although the accuracy detractors might be the same. I shoot various bullet types and would be interested to know if or how I could look for this.
I run a AA PTX which is an M style expander and the only neck tension test is measuring COL after successive chambering, and an unscientific thump test. I would think a consistent neck tension would provide better grouping, but wonder if there’s a “tension node”, similar to a velocity node where some amount of tension would provide good precision but the groups would be independent of the amount?

Bolt action reloading did a bunch of neck tension testing in 223 and there is a second video about the short action customs bushings. All the graphs one could ever want.

 

[lordpaxman]

I've like many others have done OAL testing when we have finished a load workup. On 9mm I saw group sizes reduce with shorter OAL by significant amount, 1/2 reduction.

That’s very interesting, I’m going through some COL testing right now and see group sizes reduce with increasing COL. This is with coated bullets and I’m see reductions when in the 1.140 - 1.160” range, heavy bullets, fast powder. I’m sure there’s a lot of factors coming in to play, it’s a matter of which are more important.

 

[BJung]

That’s very interesting, I’m going through some COL testing right now and see group sizes reduce with increasing COL. This is with coated bullets and I’m see reductions when in the 1.140 - 1.160” range, heavy bullets, fast powder. I’m sure there’s a lot of factors coming in to play, it’s a matter of which are more important.

What caliber are you shooting?

 

[lordpaxman]

What caliber are you shooting?

This is 9mm, competition loads, shooting for minimum 130 PF, 147gr Blue Bullets both RN and TC, Sport Pistol, P320 X5 Legion, Red dot. Shortly will be doing the same COL ladder with RMR MWs, 147 and 135’s, and trying N320 as well.