Some years ago I bought this jug of military surplus SR4759. Apparently it came from disassembled ammo. I knew that when I bought it, and I got it at a very good price.
If you were to look closely you could see small flakes of brass in the powder, as well as what look like flecks of a black sealant. There's not much in there, but you can see it if you look.
What I've been doing is pouring the powder onto a slanted piece of cardboard. With a little tapping the powder kernels roll down the cardboard and the brass and sealant specs get left behind.
My "processed" powder works just as well as normal SR4759.
I'm wondering if I need to go through this extra step. If I didn't I could see a very few brass flakes and some specs of the sealant getting left in the bores of my guns.
Do you think this could be a problem?
Personally I don't think the flakes would cause a problem, but I process it anyway just to be sure.
Anyone ever run into a situation like this?

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I think your technique is slick and it gives you peace of mind, and anyone that crafts their own ammo should recognize the value in knowing that you did your level best to make great ammo. I mean, I can certainly say this for myself. Pride in what I make shows up in my results. I have confidence in my ammo that translates to great shooting and I'm sure of that.

So don't discount your process that has worked.

With that out of the way, I also decided about 28 years ago that it was preposterous for me to clean primer pockets and so I will not EVER do that nonsense again, but my handloads are still absolutely fantastic.

Along those lines... I think that removing of those bits of impurity probably isn't much benefit and if I were in your position, I wouldn't do it. The tiny occasional brass bits will be blown out with each shot. If you have any "left in the bore" it would only be from the last round fired and none previous. And the flakes of sealant are getting beyond incinerated I'm sure.

That doesn't mean you should stop, this is simply how it occurs to me.

The only thing that I would worry about is that these "contaminants" will tend to settle and be more heavily present in powder from the tail end of the can than from the top of the can. That might, on a percentage basis, reduce the effectiveness of the powder. From my general read of your post I am guessing that this is unlikely as the contamination level is so low.

Don't know if you guys are aware but SR4759 has been discontinued, and it is highly sought after by cast bullet shooters, and that's what I am. So this powder is very valuable to me.
I will watch it as it gets low to see if there are more contaminants in the bottom. I'm not near there yet and hopefully that day won't come for a while. I processed some yesterday and there were very few flecks in it.

I would keep doing what you're doing. I would do the same thing, if it were me. It would bother me that the debris was in there, and if you weigh your powder charge-you'd be weighing the debris also. BTW, I still clean my primer pockets :-)

The sealant is only lacquer or asphalt based sealant and normally is fired in the gun when shooting military ammo , I've shot several thousand through 1903-A3 with no harm .
The Brass Flakes ....well brass is soft so it shouldn't damage a barrel and it takes a high heat to melt brass . Even if the brass melted in the barrel it would only present a fouling similar to bullet jacket fouling .
I would remove the largest flakes of brass , simply for piece (peace) of mind and load it ... there shouldn't be a problem that a bore brush and solvent couldn't take care of at worst .
Load up and fire 20 - 50 and see how the bore looks .
Gary

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Certified Cajun
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I had some WC 820 surplus that showed some contaminant flakes but chronoed the same as the base it was compared to . [AA9]. I wouldn't go to the bother but do what works for you.

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Front sight and squeeze

I use a lot of SR 4759 in cast bullet loads and I stocked up on it when it was announced that it was to be discontinued.

I had no idea that it was sold as a surplus powder. I've burned a lot of surplus 4895 and 4831 over the years, but never surplus SR 4759.

What military ammo do you suppose that it was loaded in?

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Keep your powder dry.

As we are both hobbyist handloaders, I would offer up the idea that you take whichever caliber/firearm/handload you hold nearest and dearest to your heart that of all you make or have made, would be the benchmark for accuracy of anything that you produce...

...and for the pure science of it, build a box or two of that ammo doing every single bit of it the same as you always do EXCEPT do not clean those primer pockets, find the rattiest filthy pockets you can find, make that ammo, test it to the best of your ability in great conditions and see what you see.

I love making ammo but primer pocket cleaning is physically taxing and basically a prison sentence to me. If you enjoy doing them then all is well. But you could possibly find that this step can be eliminated.

According to a post in Paco's lever gun forum:

"In spite of the SR (Sporting Rifle) prefix, 4759 was developed for military application during WWII.
It was a bulky powder for reduced loads with "frangible" bullets for use in air to air gunnery training."

Doesn't say exactly what rounds but air to air was .308, .50, and some 20mm.
I'd guess they were training with 30-06 and .50 BMG.

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NEMO
"Everything 44"

I was advised by a twice Distinguished Pistol shooter that the graphite in the old Bullseye powder will also settle. So based on his recommendation I store my jug powder on their side and flip the jug every 6 months. Not sure it helps but it don't hurt.

I would make a batch of 20 rounds of cleaned powder and 20 rounds of contaminated. Do some testing and see what you can find out. That's what I like about reloading, doing some safe experimenting to see what works for me. Otherwise, if you are satisfied with the results from cleaning your powder, don't change a thing and continue doing what works for you.

Interesting. I recall reading about the P39 Aerocobra aircraft that were used as target planes for the frangible munitions. Apparently they had lights that flashed on and off when they were hit. I'm not sure I'd want to be a pilot in one of those although it was probably fun to shoot at them.

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Keep your powder dry.

Did your surplus 4759 come in a white bottle that looked like it originally held Chlorox bleach? I've got one of those (about 8 lb) that I bought back when I was shooting a lot of 32-40 in a high wall Winchester (ASSRA events.) I bought up a bunch of that powder from whatever sources I could find back in the '90s and early oughts. I've heard it was the replacement for the old #80 powder from earlier in the 20th Century.

Froggie

Aircraft skin is very thin, even on the P39. Air-to-air gunnery was conducted by shooting at a towed banner, often with the tow plane piloted by women pilots.

Sevens, Good Morning Neighbor!

I de-prime and wet tumble with stainless steel pins, my primer pockets come out as clean as the brass! If I clean without the pins, the primer pockets will still have some residue, but not much/not bad. When I shot PPC, I made sure my match brass was prepped/trimmed and kept separate. I still sort my brass by headstamp (all calibers, all the time lol). That's just me Even though I don't shoot competition these days, I still want the best ammo I can make and I'm retired now!!

4759 WOW,I'm down to my last 2 pounds and am beginning to have nightmares if they don't reintroduce it.
Possible to let us into the info where you got it?

I don't deburr 357 or 44 mag brass. Trim to my correct dimension, resize and reprime brass (knocks off outside burr), flare case mouth (knocks off inside burr) and load powder, seat bullet, crimp case mouth.

Don't worry about little brass flecks. They go down the barrel with bullet, flame, and gas. Somethings are too small to worry about in life.

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S&WHF 366