All Brass Is Not Equal

[sixshot]

Recently I've been shooting a new Bobby Tyler 45 Auto Rim that was built from the ground up on a Ruger OM 357 frame. The gun is shooting great with 3 different bullets & powders but I'm not surprised.
What did surprise me, & I keep forgetting to mention it is, the difference in brass. Many times, six gun prophet John Taffin has cautioned against mixing different brands of brass, especially in the smaller calibers or capacities. A 45 Auto Rim is basically the same capacity as a 45 Auto, not really a lot of powder. In a 9mm it can really become a problem, trust me.
I started out from day one using new Starline brass, which is known to be of high quality & lasts for a long time, some of mine has now been fired 4 times & is still going strong. Also on the shelf was some factory PMC 45 Auto Rim so I shot some of it and then weighed both cases, Starline & PMC, what a surprise!
The Starline tipped the scales at 88 grs, while the PMC weighed in at 99 grs, yikes! You can see that if a person worked up to what you consider the mythical maximum load using the Starline brass & then dropped the same charge into the PMC brass you could very easily get a pressure spike, especially with a fast burning powder.
That's why you don't use someone else's loads, ever without working up from 2-3 grs below. Changing anything always changes everything!

Dick

[JimB..]

People talk about this, but I wondered if it was really likely to be dangerous, so decided to try some math.

The density of yellow brass is 0.306 lb/in^3 which works out to 131.5 gr/cc.
Your cases were 11gr apart, which works out to a hypothetical .083cc difference in volume (this is almost meaningless, the vol could be the same or not, we’d need to look at the case design to see where the weight is, but it’s what we have to work with unless someone wants to measure the case capacity)
A 45acp case has a capacity of about 1.62cc.
So the .083cc difference is right at a 5% difference in case capacity.

Unless you’re loading right at the ragged edge, I can’t image 5% makes any difference in terms of safety, and I wouldn’t bother to work up a new load.

I don’t shoot other people’s reloads, but not because I’m afraid of mixed brass.

[Winger Ed.]

It's common to sort rifle brass for that reason.
Not that the difference in wall thickness or volume will cause a rifle to blow the bolt out through your ear,
but at longer ranges the little bit of difference in pressure can lead to a larger group than if the head stamps were all the same.

Same with handguns but at the shorter ranges, its less likely for the accuracy or speed/pressure differences to be noticeable on the target.

[JimB..]

Hey @sixshot, just reread my post and I kinda come across as a horses behind. That wasn’t my intention, I wrote the post while doing the math on a post-it note, was really curious how much it would matter.

While I reload mixed 9mm brass I scrap the brass with the step inside, the volume difference with those seems huge.

[ReloaderFred]

My question to these kinds of posts is always the same; where is the actual weight difference? Is it in the case wall, base, rim, neck, etc. If it's in the case wall, base or neck, then it "may" have an effect on volume, but if it's in the rim, then it makes no difference at all.

Checking case volumes makes much more sense to me, and I don't do that, either, but I believe that's what would truly make a difference, not plain case weight, when we don't know where the actual difference in weight comes from.

Hope this helps.

Fred

[sixshot]

While I didn't do a water capacity test I did load both cases with the same amount of powder and it was visually obvious that the PMC had less capacity than the Starline. Enough to be dangerous, that's up to the shooter I guess.

Dick

[ReloaderFred]

I've generally found that PMC handgun brass (that which is actually made in South Korea) is normally heavier in construction than domestic handgun brass. They also use a different priming compound, which produces a white residue. I've tried to find out what the priming compound is at the SHOT Show several different times over the years, but the language difference really complicates communication. All I could get was "no, no, not corrosive", in a heavily accented English.

When PMC was an American company in Boulder City, NV, their brass wasn't as heavy in construction, but when it went back to South Korea, it reverted back to what it was before it came to the U. S. for that period of time it was here.

I don't doubt at all that the PMC brass has a smaller volume, due to my past experience with it. My question is only for those people who make blanket statements about case weight, without actually testing to find out where the weight is on, or in, the case. It wasn't meant to disparage your post at all, sixshot.

Hope this helps.

Fred

[rintinglen]

And before I came to the realization that the middle is safer than either edge, I once weighed two different lots of federal 38 brass and came up with about a 4 % variance between them. Now I stay away from the bottom and the top for most of my shooting, just in case I run into a case or boolit that is a little outside the norm.

[sixshot]

Fred, no problem, I kind of discovered the difference by accident. When I first sized some PMC 3 rounds wouldn't chamber, it was just a tick tighter in the web & my custom Ruger is very tight. That's when I decided to weigh some of each & just looking at the powder in the cases it was easy to tell. No need to fill it with water, you could see it using Longshot.
Also 14.0 grs of H110 & the 223 gr SWC HP shot great at 50 yds! Do not use any of these loads in your Auto Rim. The small holes in the 50 yd targets were already there.





Dick

[44MAG#1]

I think this is a great subject, not necessarily about the difference in cases, but that there are differences in components period.
I have Starline, Winchester, Sig and Rem. cases for the 40 S&W. When using the Hornady 200 grain XTP Sig is the only one that shows a pronounced bulge where the base of the bullet rests after being seated to 1.125" OAL. The internal capacity of the sig cases is less. In the other cases I use the powder charge interchangeably. I don't use Sig cases with the 200 grain bullets. Even Sig 10MM cases have slightly less capacity. All this using water cap. between Starline and Sig cases.
But to carry this farther cases aren't the only thing to watch out for. Powder lots should be examined too. I posted this before but was soundly questioned by some by asking questions, it seemed, leading up to disparaging my results. But here the are again. On 4-17-19 I chronoed two different lots of 2400 in my M629 4 inch 44 Mag S&W. Both loads were chronoed back to back. With the other components being the SAME lot 785-Y081016 yielded 1273 FPS average velocity while lot 789-X062118 yielded 1130 FPS average velocity. The charge was 20.0 grains of 2400 with the Fed.150 primer The ONLY difference was a change in lots of 2400. Now I know, according to some, this shouldn't be, but it is.
A primer test I ran with everything else being the SAME shot from an Encore 44 Mag barrel that was shortened to 6 19/32 inches with the loads chronoed back to back using Federal 150, CCI300, Remington 2 1/2 and Winchester LP the lowest velocity was 1316 FPS and the highest was 1376 FPS.
Lets just remember difference can add up whether case capacity, different lots of components etc.
Again this threads value is more than just reminding us of differences in cases but differences in "lots" of components and techniques too.

[Paul105]

Regarding 2400 (In this case it was Hercules 2400).

Way back in the early 70s when I got my first chrono -- 21.0 gr Herc 2400, 250gr 429421, same case, same primer but different lots of powder - velo diff from a 7 1/2" redhawk was 150 fps -- really surprised me, but made me cautious when changing "lots" of anything there after.

Just another data point FWIW,

Paul

[dbosman]

The possible differences in brass is why I recommend sectioning some of each lot or batch. With a cutting tool like a Dremel sectioning takes very little time. Flatten the brass and measure thickness a bit off the rim, in the middle and at some arbitrary, but consistently used, point above the base. A sketch of the results, or now digital photos, and the measurements can be kept with your load data. Add water weight for capacity comparisons.

[lar45]

What really matters when it comes to brass is the internal capacity.
It is not that hard to measure the water capacity.
Use an electronic scale.
Place an empty case on the scale and "tare" it
Then fill the case with water to the top and put it back on the scale.
Now you have the water capacity.
You can measure a few and get an average if you want to.
Switch brands of brass and repeat.
Take notes so you can look back later.

I've been working with an AR pistol in 7.62x39 and weighed 4 different brands of brass just to see what I had to work with.
PMC 124.3case, 35.3H2O
PPU 117.4case, 35.6H2O
Win 128.8case, 34.3H2O
Lapua 133.0case, 33.4H2O

When I first started loading 45acp, way back when, I gathered up a pile of TZZ Military brass after a shoot on the ship and took it home to load. My buddy was using 4.7gn of 700X with a 230 LRN for about 900fps in commercial brass. So I used that load in the TZZ brass and went to the range. I got around 1300fps. I went home, pulled all the bullets, started way low and worked back up to 4.2gn 700X which gave about 900fps.
Yes, it is military brass and I was stupid for not backing off 10-15% at first, I'm just relaying this story to show that the difference in case capacity can make a huge difference.

[.429&H110]

dbosman +1 for the dremel.
my reload teacher had me
quarter lengthwise a dozen
44 mag brass
kinda anatomy lesson
Some places are very very thin
They don't stretch evenly
Sometimes there's crud in the bottom.
He said only use Starline
I've never been picky
Somewhere previous saw
19gr H110, 300 grain hard lead
That was my "bear load"
It hammers, but set too deep,
YMMV