44 Mag, different brass, different velocities

[Stats Shooter]

I have been experimenting with the 44 mag and the Speer GDHP 240 gr bullet lately and had an interesting result I thought I would share.

I made up a load using the 240 GDHP, 24 gr H110 and CCI 350 primers.

I had 100 pieces of Federal, and 100 Pieces of Remington brass. Both sets fired twice and trimmed to same length.

While loading on a Dillon 550 with Lee crimp die in position 4, I alternated pieces of brass as I fed them into the machine. I.e federal, rp, federal, rp etc etc.

I shot about 25 of each over the chroney and interestingly the federal averaged 25 fps faster than the RP. The RP was around 1385 fps and the federal around 1410.

You could also see a difference in the primers. I checked COAL coming off the line of several and they were pretty much all the same.

I have noted differences in brass before in other cartridges but it was always either batch loaded or a grab bag of mixed headstamp which wouldn't be the most scientific of tests.

But I thought the results of this little exercise might interest yall.

[jmr40]

That is very common. The actual case capacity of different brands of brass is slightly different. Federal brass is well known to have slightly less volume than other brands. As a result the same powder charge in Federal brass results in more pressure, and more velocity. This can be a problem when working close to max loads.

All brands are slightly different, but I've never noted enough difference between Hornady, Nosler, Remington, or Winchester brass to matter. I can tell a difference with Federal. Military surplus brass is similar to Federal in this regard.

It is generally less of an issue with handguns. But with rifles I separate all my brass by brand. That small difference in case volume, pressure,and velocity can make a difference in downrange accuracy. And a load close to max in one brand of brass may be overloaded in another.

[IMtheNRA]

Did the slower load also have higher SD numbers? If so, I'd suspect lower neck tension in one type of brass is responsible for slower velocity.

[Stats Shooter]

Did the slower load also have higher SD numbers? If so, I'd suspect lower neck tension in one type of brass is responsible for slower velocity.

An SD with so few observations would be statistically insignificant. I'm not trying to be a jerk, but I don't post or even bother to calculate an SD from such a small sample.

As for there being softer brass, that's a possibility.

[black mamba]

Neck tension and case capacity are the two contributing factors I'd guess. How did they group? Did all bullets print to the same point of impact? I've always been able to shoot pretty decent groups with mixed brass, in several different calibers.

[buck460XVR]

Originally Posted by black mamba

Neck tension and case capacity are the two contributing factors I'd guess. How did they group? Did all bullets print to the same point of impact? I've always been able to shoot pretty decent groups with mixed brass, in several different calibers.

^^^This. Actual velocity means very little to me as opposed to how accurate a load is.

Originally Posted by Mississippi

An SD with so few observations would be statistically insignificant. I'm not trying to be a jerk, but I don't post or even bother to calculate an SD from such a small sample.

Then why would you be concerned so much over a 25fps difference in velocity from such a "statistically insignificant" observation? Why would SD be any different? IMHO, 100 rounds is not a insignificant amount. Many times when working up a load, I load in batches of 10 and calculate the SD and velocity to evaluate performance. Still, in the end, most of the time, where the holes on the target end up is what determines the load I use.

[IMtheNRA]

Your sample group's SD would be as "insignificant" as your velocity data that you posted.

[buck460XVR]

From my experience, R-P brass is a tad thinner than Federal, thus it probably would give more case volume and less neck tension, and thus may produce a tad less velocity.

[Stats Shooter]

Your sample group's SD would be as "insignificant" as your velocity data that you posted.

Um, sort of. I didn't claim it was the population mean, just a sample average. 25 fps as a percentage of the highest velocity tested is with 25 obs is enough to claim an average is higher than the other given the low deviation from the sample mean. Mean reversion usually happens faster (fewer obs) than other statistical measurements.

However, comparing SD's across samples with different means is improper. The SD is a within sample statistic since it it is nominal. i.e. if a velocity is 2500 fps with SD of 50 and another cartridge has an average velocity of 3000 fps and an SD of 55, the 3000fps sample is less variable.

If you want to compare sample variance with different means you would use the SD÷Mean=CV or coefficient of variation because this ratio is unitless.

This. Actual velocity means very little to me as opposed to how accurate a load is

I agree with this, but if someone is working near max loads, it would be useful to remember that if you change cartridge head stamps, you need to drop the charge down and work back up again. This is just an example of why.

From my experience, R-P brass is a tad thinner than Federal, thus it probably would give more case volume and less neck tension, and thus may produce a tad less velocity.

That's what I think, or something like that. It's interesting though how many folks just take these things for granted that brass is brass and it's all the same.

[buck460XVR]

Originally Posted by Mississippi

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It's interesting though how many folks just take these things for granted that brass is brass and it's all the same.

I think it's just a matter of "good enough for what it's for", and relative to the shooter's perception/needs. Kinda like trimming handgun brass. Most folks claim it's not worth the effort and it makes no difference. Probably doesn't with mild to medium loads at ranges of 25 yards or so(which is what most folks shoot). Start shooting heavy hunting type loads at distances of more than 50 yards and IME, it makes a considerable difference, similar to using mixed brass. Folks shooting reactive targets like gongs aren't looking at hitting the ten ring every shot, they just need to hit a 8-12" piece of steel someplace. Big difference.

[Stats Shooter]

Most folks claim it's not worth the effort and it makes no difference. Probably doesn't with mild to medium loads at ranges of 25 yards or so(which is what most folks shoot). Start shooting heavy hunting type loads at distances of more than 50 yards and IME, it makes a considerable difference, similar to using mixed brass. Folks shooting reactive targets like gongs aren't looking at hitting the ten ring every shot, they just need to hit a 8-12" piece of steel someplace. Big difference.

Sure.. My Hunting, match AR, and F-CLASS rifle loads are put together with a lot more scrutiny than my handgun and steel target AR ammo