45 ACP; powder lot difference - Power Pistol

[Nick_C_S]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

Well folks, I was getting down to the last of a # of Power Pistol and thought I'd run the same experiment with it as I did with Unique.

For those who remembered or cared, the experiment with Unique was an eye opener; but mostly because of the switch to the more confining Starline+P brass.

This time, I ran all Starline+P brass so that element is missing. This experiment is strictly the difference in powder lots. Time for some history:

The "old" # of Power Pistol has a lot number that suggests it was produced on 3/31/14. I purchased it on 5/9/14; and first opened it on 5/21/15. (Yes, I keep logs of all this stuff). Last used 7/29/18 - for this experiment, of course.

The "new" # of Power Pistol is actually a 4# canister. The lot number suggests it was produced on 5/11/15. I purchased it on 6/11/15; and first opened it on 7/29/18 - for this experiment, of course.

For the record, this is the first time I ever bought powder in any container exceeding a #. I'm very fond of Power Pistol and have more than enough confidence in its performance to know it's going to remain a mainstay of my powder inventory. Hence, the 4# purchase.

Like last time, this experiment will be with the same volume of propellant between the two lots. Not the same weight.

The bullet used is an Everglades 230gn JHP. The length of the bullet is .637." COAL is 1.220".

Charge weight of the old lot is 6.8 grains.
Charge weight of the new lot is 6.93(ish) grains - using the same volume setting on my RCBS Uniflow. I have an RCBS 10.10 scale, and it has a drum that you can roll to exact amounts - not just 0.10 grain detents. Hence, the ".93" grains. I sampled four throws of each - and more throughout the case charging process. Power Pistol meters much nicer than Unique (duh).

QuickLoad guestimates 21766 psi and 920 f/s for the 6.8 grains.
QuickLoad guestimates 22741 psi and 937 f/s for the 6.93 grains.
So these would be considered +P rounds. On paper and in reality, these were stout 45 ACP rounds. CAUTION: Do not use my data for loading purposes; as your results may vary. Please do your own load work ups by starting low and working up in small increments.

I loaded 50 rounds of the old powder and it measured consistently 6.8 grains throughout the charge process. There was enough remaining powder to make about 20 more rounds - it became lawn fertilizer. I then filled the hopper with the new lot and weighed several throws. They all weighed 6.93 grains - consistently. The 0.03 grain part is and "eyeball" on my part; as the drum on the scale is incremented by 0.1 grains.

I then loaded 50 rounds of the new propellant and it measured consistently at 6.93 grains throughout.

Gun used is a Kimber full-size 1911 (5" bbl). Chronograph at four yards. Temp = 68f and smokey (from the Carr fire about 200 miles north of me); slight south-west breeze coming from 6-o'clock (tailwind). 25 round samples each.

Old lot: 6.8 grains - 924.0 f/s; 16.78 SD
New lot: 6.93 grains - 927.6 f/s; 18.75 SD

The difference between the two lots was statistically insignificant . . . by VOLUME, that is. By weight, I would suspect a 10 to 15 f/s drop with the new propellant.

This experiment confirms what I have gleened over many years of casual observation: That propellants lose density after they have been opened. I suspect the loss in density is water. I live in a dry climate. There have been a few times over the years where I did a load work up for fairly hot ammo (usually 357 Magnum) and I coincidentally did the work up with a new # of propellant. Then some time later, I load a batch near the end of the # and I have on my hands excessively hot ammo - which left me scratching my head and wondering where I went wrong. Now I know what I have suspected for some time.

Moving forward, I will set this loading at 6.7 grains. Hopefully, by the time I get to the end of this 4# container, it won't be too hot. And speaking of this 4# container: I opened it, dispensed a pound into a separate 1# bottle. The remaining 3#'s won't be reopened until I need another #. And yes, on the 1# bottle (which is a Power Pistol bottle), I have thoroughly marked it with the correct lot number, etc.

Next up will be HP-38. I have a # that is nearly empty. I will run this same type of experiment again. It'll be 45 ACP and a 200gn LSWC, using 5.0 grains - a recipe I've been loading since 1985. What will be different with this upcoming experiment is that the new # of HP-38 happens to be of the same lot number; so the only thing that'll be different is that the old # has been opened for some time. Should be interesting - I hope.

 

[kmw1954]

Interesting. Don't know how I would apply that but still interesting.

I have pretty much seen the same while just using the fixed cavity of the Lee Auto Disk. Even though I have a load that I always use the same powder and the same disk cavity from loading session to the next session I weigh before I start and almost always see a slight variation. Which I then record in my log book. I just see it as the nature of the beast!

 

[Nick_C_S]

Interesting yes. But not earth-shattering. I agree. To me, it does show the advantage of powder drop bars, or any other fixed type volume metering devices.

Propellants lose density over time (or at least they do here with this dry climate). And that brings a drawback of using weight (or mass) measuring devices. Your ammunition's performance will change.

 

[Unclenick]

It's good information. I would suggest taking enough power pistol for maybe 50 rounds and weighing it and leaving it spread out on a plate to dry and then reweighing it every day until it stops changing density, and then run another 25 rounds to see if you get the QL predicted 17 fps change. Your standard error for the two velocity errors combined was about 5 fps. Because your mean difference is less than that, you are correct that the 3.6 fps difference in velocity gives you little confidence that the velocity difference you measured is real and not random. But if the drier powder gives you the velocity difference QuickLOAD predicted, and the SD doesn't change, you will have pretty good confidence the difference is real and not random. Just 10 fps difference would up the confidence considerably.

 

[kmw1954]

Nick_C_S, Having worked for 17 years in a company that did nothing but deal with organic and herbal powders and packaging them in 1/4oz to 1# bags I find gun powder to be no different. All powders will gain and lose moisture content over time and depending on how they are stored. Just as wood will swell and shrink as it gains or looses moisture. Moisture can add weight or volume to very different degrees depending on the substance. It can also change burn rates as you have seen. Or with organic powders with too much moisture it can begin to mold which causes heat which causes spontaneous combustion.

Anyways, again thanks for the report and experiment. You seemed to enjoy it. If nothing else you have given yourself a little insight as to what's going on.

 

[Nick_C_S]

If nothing else you have given yourself a little insight as to what's going on.

Exactly. I've been doing these tests for my own knowledge and just thought I'd share.

I didn't know smokeless propellant contained any water moisture at all. For some reason, I always viewed gun powder as basically unchanging. Not sure why I thought it'd be different than everything else in the universe .

 

[Jim Watson]

Great, I was looking at doing similar trials, but just on a run of pile basis after a new keg opening. You are much more organized. I'll be interested to hear what you get with HP38. My last purchase was clearly, if slightly, less dense than the previous lot. But that lot was indistinguishable from the one before.

Smokeless powder is a plastic, mostly nitrocellulose. Same chemistry as an old billiard ball or celluloid collar, just at a higher level of nitration to be a propellant instead of just a flammable solid. Not much moisture in a billiard ball; I figure whatever is present in powder is a surface effect, the amount depending on humidity.
But powder has residual solvents, the smell in a fresh can of powder. That will volatilize in time, the only change being downward.