.015 Variance in 9mm COAL

[Meangun]

In everyone's opinion, what is an acceptable range of variance when loading 9mm 124gr Hollow Points that call for a COAL of 1.060"

 

The brass is a cornucopia of brands as this is pick up off the range of the PD i work for. The only reason I have been checking multiple loaded rounds now is that I'm loading for my Sig P226 X-Five.  

 

COAL ranges from 1.060-1.075 

Mixed Brass

GM100 primers

VV N330

Xtreme 124 HP

550 B

#1 Dillon Sizing

#2 Dillon Flare/Powder

#3 Dillon Seater (RN Stem)

#4 Lee FCD

 

Thanks in advance for any input.

Edited August 17, 2023 by Meangun

[GrumpyOne]

What press?

[Meangun]

5 minutes ago, GrumpyOne said:

What press?

 

Sorry! And I meant to type that too! lol

 

550 B

#1 Dillon Sizing

#2 Dillon Flare/Powder

#3 Dillon Seater (RN Stem)

#4 Lee FCD

[GrumpyOne]

How did you set your press up? With a case in every station? The shell plate can rock some if you try to set it up without a case in every station. In other words, load 2-3 fulle rounds, then check the one in the seat station, leaving all others on the press...then adjust the die to the OAL you want. 

[Meangun]

Press was set up exactly as you described. Case in every station to keep the same amount of pressure on the shell plate so there is no flex when the ram is up, dies are down and locked in place.

[GrumpyOne]

Gotta be the brass then. I used mixed brass, pretty much same setup, but I'm getting much less variation...like .005

[BJB]

2 hours ago, Meangun said:

COAL ranges from 1.060-1.075 

Mixed Brass

GM100 primers

VV N330

Xtreme 124 HP

550 B

#1 Dillon Sizing

#2 Dillon Flare/Powder

#3 Dillon Seater (RN Stem) ...flip this over and use the flat side of the stem for hollow points. 

#4 Lee FCD

flip the seating stem to the flat side.

Edited August 18, 2023 by BJB

[Meangun]

13 minutes ago, BJB said:

flip the seating stem to the flat side.

Thought about that before I started reloading the rounds. Called Dillon and they said use the RN side as there was plenty of ogive for the stem to reference on the HP bullet to center and seat against. Flat side should only be used with semi wad cutters where there is no ogive to reference off then you'll be at the mercy of the consistency of the bullet lengths regarding COAL.

[BJB]

3 minutes ago, Meangun said:

Thought about that before I started reloading the rounds. Called Dillon and they said use the RN side as there was plenty of ogive for the stem to reference on the HP bullet to center and seat against. Flat side should only be used with semi wad cutters where there is no ogive to reference off then you'll be at the mercy of the consistency of the bullet lengths regarding COAL.

Real quick & easy to flip it, load 10-20, and measure. 

[Meangun]

Just now, BJB said:

Real quick & easy to flip it, load 10-20, and measure. 

no doubt about that and I will try it!

[SnipTheDog]

9mm measured COAL is about +-0.003 on the 1050.  Need to make sure the you're not measuring with a proud primer once and a while.

[HOGRIDER]

Search will turn up some great resources...........

 

[Farmer]

HP’s can also be a bugger with various mouth dimensions. I also use a flat punch with everything except RN with better results. 

[fbzero]

Honestly, probably just tolerance stacking.  You have the normal press variation, the variation of mixed cases and the very slight variation in the projectiles all adding up.  Mine seems to be around 0.01 with similar circumstances on a 1050, and that's with flat tipped projectiles that seem to be more consistent.  Probably 90% of them are within .003, then there just ends up being a random one that is further outside of that.

Are your rounds accurate at reasonable pistol distances?  Do they all chamber without issue and pass the case gauge?  Unless there is some practical problem, I wouldn't spend too much time worrying about it.  Pistol distances are much shorter and we don't need to be as meticulous as if we were loading for precision rifles.

[Dr. Phil]

+1. I have been following and wondering what the problem is with that tolerance. Too small for any worry IMO. 

Maybe try 1 brand of cases for a short run and ee if you feel better about it?

[IVC]

That's a lot of variation. 

 

Mixed brass is overrated for OAL variations - the seating die will push either on the bullet tip or the ogive and the OAL will be controlled by the distance between this contact point and the bottom of the shellplate. This distance doesn't depend on what brass is in, or even how long, wide or thick it is. The two primary uncontrolled variables here are the small variance in the position of the shellplate, and the variance in the bullet shape when contact is with the ogive (when contact is with the tip, it doesn't matter). This is a pistol round, there are no considerations about the location and angle of the (non-existent) shoulder. 

 

For test, I would first flip the stem to the flat side to ensure all bullets are pushed to the exactly the same position inside the die, then measure the variability. This is not because it's the correct setting of the die for the bullet you're using, but to determine if the length variation is due to the inconsistent ogive. You don't even have to readjust the die, even though your OAL will be completely wrong - all you want to do is determine *consistency*. Measure ten rounds and look at STD and ES of the length. If you get a good spread, the problem is the bullets. If you don't, and you still get a lot of variability, it must be something with the shellplate.

 

As the last test, I would try seating on another press. There is a slight possibility that other dies are too low and interfering with the movement of the toolhead (or shellplate in your case). The 0.015" is on the high side and I would only accept it if it's from the inconsistent bullets, but not if it's related to the press or the dies. 

[Joe4d]

the shell plate base doesnt move.. the moving part pulls the brass out of the dies, it doesnt push them up. Your brass will bottom out on the base on a 550. 
Make sure your primers are flush or below flush and not throwing off your OAL measurements... Could also be a stroke issue, you really arnt going all the way  down every time.  There is also play in Dillons seat die, I really dont like their seat dies. 

[IVC]

1 hour ago, Joe4d said:

the shell plate base doesnt move..

Is it a turret? I'm not quite familiar with the 550...

 

But in any case, the OAL is determined by the mechanical properties of the press and the bullet, not the brass. At least not in a direct way. 

Edited August 18, 2023 by IVC

[Joe4d]

1 hour ago, IVC said:

Is it a turret? I'm not quite familiar with the 550...

 

But in any case, the OAL is determined by the mechanical properties of the press and the bullet, not the brass. At least not in a direct way. 

in the 550, the brass sits on a flat surface, there is a rotating shell holder that holds the groove of the case,, or in a rimmed cartridge the rim goes under the shell plate. Any upstroke action the brass will hit the smooth flat surface of the base which is attached to the ram.. The dies are stationary.. Usually you adjust the shell plate down so it is too tight to rotate if the primer isnt flush.
But yes you are right,,, The OAL will be the distance between the base that comes up, which is fixed assuming you do a full stroke and the bottom of where ever the seating stem hits the bullet.
The only point of play is a small amount in the tool head, and in his case a dillon die has a bit of play. If he has that bad an OAL,, he either has high primers, or bullets with inconsistent OAL's Like one has a sharper nose than another. Or not consistent on down stroke. OR is bullet sticking in die ? like its seating then being pulled back.?

[shred]

Make sure the case is being sized enough.  Pull a few after the sizer and try to stick a bullet in.  If you can, there will be major OAL and setback issues. 

 

[ddc]

7 hours ago, IVC said:

That's a lot of variation. 

 

Mixed brass is overrated for OAL variations - the seating die will push either on the bullet tip or the ogive and the OAL will be controlled by the distance between this contact point and the bottom of the shellplate. This distance doesn't depend on what brass is in, or even how long, wide or thick it is.

 

I disagree.

 

Sort out 20 cases of CBC, 20 cases of Blazer Brass.

Load 'em up.

You should see that your CBC loads have a slightly longer OAL that the Blazer.

It may not be a lot but it will be there.

 

I sort for headstamps. Typically Blazer, FC, WIN, SB, CBC until I have at least 1k to load.

I tune my seating stem so that my OAL adjustment is currently 1.130.

When I go from CBC to Blazer I have to back off a bit for same OAL.

When I go from Blazer to CBC lower it just a tad bit.

 

It's repeatable. It's not enough to worry about unless you're OCD. But it's there.

[IVC]

56 minutes ago, ddc said:

I disagree.

 

Sort out 20 cases of CBC, 20 cases of Blazer Brass.

Load 'em up.

You should see that your CBC loads have a slightly longer OAL that the Blazer.

It may not be a lot but it will be there.

Where is the extra length coming from? If both cases sit flat on the same surface and if the distance from that surface to the point of contact between seating stem and the bullet ogive is the same, where is the extra length "stored?"

[Farmer]

2 hours ago, IVC said:

Where is the extra length coming from? If both cases sit flat on the same surface and if the distance from that surface to the point of contact between seating stem and the bullet ogive is the same, where is the extra length "stored?"

Internal taper differences, brass thickness, brass hardness. If you have brass that is firm, thick and has a quick internal taper, (CBC) it is going to take more effort to seat the bullet to X length because of the forces working against you plus the little bit of Push-back you get. I did a test where I took CBC brass, seated a bullet quickly and measured it. Then took the same brass and seated a bullet but held it down for a slow 5 count and that one was seated where I had set the die for other brass. There’s a lot more flex in everything than you think, and if you don’t think it takes a fair amount of force to load a round just put your finger between the shell plate and die and push on the lever! 

[ddc]

2 hours ago, IVC said:

Where is the extra length coming from? If both cases sit flat on the same surface and if the distance from that surface to the point of contact between seating stem and the bullet ogive is the same, where is the extra length "stored?"

 

11 minutes ago, Farmer said:

Internal taper differences, brass thickness, brass hardness. If you have brass that is firm, thick and has a quick internal taper, (CBC) it is going to take more effort to seat the bullet to X length because of the forces working against you plus the little bit of Push-back you get. I did a test where I took CBC brass, seated a bullet quickly and measured it. Then took the same brass and seated a bullet but held it down for a slow 5 count and that one was seated where I had set the die for other brass. There’s a lot more flex in everything than you think, and if you don’t think it takes a fair amount of force to load a round just put your finger between the shell plate and die and push on the lever! 

 

Exactly. The differences in brass thickness, brass hardness, all the esoteric individual variables that apply to a materials science analysis of a metal... they are all real and they have an effect however small they might be.

 

In a perfect, theoretical world where every manufacturer uses the same brass formulation and the same wall thickness and every piece of brass from these different manufacturers is exactly the same from one producer to the next? Then there would no effect on OAL... but that is not the real world. There are differences between head stamps and they do matter. 

 

Do the experiment. Load up a bunch of a know "tough" headstamp brass... ideally CBC or S&B if CBC not available.

Then don't change anything on your press and beg, borrow or steal some "soft" Blazer Brass and load again.

 

Measure the OAL. There will be a difference. It may be small.

 

Will it be enough to matter for your particular purposes? Very likely it will not; but I believe it will be there. Realize that if you choose headstamps from two manufacturers whose brass has very similar characteristics then the differences will not show up... i.e. the differences between a run of Blazer Brass and a run with FC brass may not be obvious because the characteristics of those two is so similar. 

 

Is this anything to worry about? 99.9% of the time I don't think so. It would only come into play if you were loading to some OAL edge condition with one headstamp and then the other headstamp put you over the line as far as chambering was concerned. (I actually just ran into this... lol...

 

If all your stuff plunk tests and goes bang when you want it to then I would bet that any other effects such as accuracy would be minimal if they were even noticeable.

 

 

 

 

[IVC]

1 hour ago, Farmer said:

...plus the little bit of Push-back you get. I did a test where I took CBC brass, seated a bullet quickly and measured it. Then took the same brass and seated a bullet but held it down for a slow 5 count and that one was seated where I had set the die for other brass.

That's a valid point, but I would argue that it's not a property of the brass itself, it's the incorrect neck tension if you're getting a "pushback." I could equally well say that if you over expand the neck and operate the press quickly, you can get an arbitrary seating depth up to the bullet falling all the way in. And I could observe that softer brass will yield more inconsistent results, even though it has to do with the neck tension and not the brass. 

 

What I am really contrasting here is properties of the rounds that directly vary with the brass (e.g., internal volume, size and type of the flash hole, crimp, quality of neck tension, etc.) vs. the OAL which doesn't. The effects we are discussing here, the latter, are at best "second order small" compared to the former.