Propellant damage from tumbling loaded rounds - an experiment.

[ATOM]

An earlier thread on tumbling primed brass brought the following comment:

Tumbling a loaded round, especially one where the powder doesn't fill the cartridge, can cause the powder to break down into a finer particle size. This can significantly increase the firing pressure, with obvious implications for safety/reliability.

OK, being naturally inquisitive, I did a bit of an experiment. I loaded a Federal .270 Winchester case with a live primer and a flat-based bullet. The charge was 50 gr of IMR 4350, which I selected because a) its tubular shape would make it easier to see if any grains had broken apart and b) I had a bunch to spare. I chose 50 gr as that allowed a little room for the propellant grains to bounce around.

Before loading, I went over the lot with a magnifying glass. There were no broken or partial grains; all of them, ie, were intact when loaded.

The completed round was put in a Frankford Arsenal Quick-N-EZ tumbler for eight hours, along with a handful of empty brass and Lyman Tufnut media with no additional additives.

At the end of eight hours, I pulled it apart and again examined the propellant. Result - no broken grains. As in, nada, zilch - 100% of the propellant grains were intact. When poured out onto a white plate for examination, there was no evidence of any very fine powder of the sort that might have resulted from the corners of the grains being knocked off.

Now this of course is hardly a proper scientific experiment. To do that, one would have to test different propellants and different charge weights in different types of tumblers. All I have proved is that this one round, using one propellant type, did not suffer any perceptible damage to the propellant. Still, it's indicative.

For what it's worth...

 

[H4831]

Excellent post. Thanks.

 

[blacksmithden]

I absolutely LOVE it when a CGN'er takes matters into his own hands and busts a myth. Thanks for taking the time to do it, and posting the results.

 

[Gatehouse]

A few years ago I read on a US site a similar experiment with the same results. Only difference is that he ran his tumbler for a week.

 

[Cummins4x4]

But now to prove your hypothesis you have to put the powder back in and shoot it. Just kidding but great thread

 

[retepnosflow]

Very Cool, thanks!

 

[Scar270]

Thanks for trying that out.

 

[legi0n]

Was it H4350 or IMR4350?

I'm asking because I've read about the shaken powder becoming faster because of it losing the graphite retardant coating rather than grinding.

IMR4350 is graphite coated while H4350 is not.

 

[Doc M]

Excellent post. Thanks.

I absolutely LOVE it when a CGN'er takes matters into his own hands and busts a myth. Thanks for taking the time to do it, and posting the results.

Damn right!!!

Sticky in the reloading section, to allow further tests too???

-M

 

[deagle2008]

your experiment went just about right but i read in an another thread that the propellant won’t break down but the small particles from your media will go into the case and causes something to not function properly but yea great work

 

[Ganderite]

As part of the manufacturing process, the fresh powder is tumbled for hours. The powder does not break or crumble.

The graphite is not a retardent. It s there to dissapate static electricity.

The retardent coating is something like DNT (not to be confused with his first cousin, TNT) and is adsorbed into the grain and cannot be rubbed off.

 

[ATOM]

Was it H4350 or IMR4350?

IMR 4350. Thanks.

 

[mlehtovaara]

your experiment went just about right but i read in an another thread that the propellant won’t break down but the small particles from your media will go into the case and causes something to not function properly but yea great work

This is about the most ridiculous thing I have heard in awhile.

Well aside from that guy claiming that .45 ACP was a suitable ATC gun for bear defence! LOL

I will have to decide which is more ridiculous. Ill get back to you?

 

[Longshot]

I have a bunch of Portuguese 308 someone gave me that was pretty corroded.I pulled out the no corroded ones and then tumbled the rest for 24 hours.
There was NO noticeable difference in POI, felt recoil or accuracy at all.
And I'm pretty sure no tumbling media got into my loaded cartridges.

 

[mlehtovaara]

And I'm pretty sure no tumbling media got into my loaded cartridges.

Where would it get in?

The primer and bullet are pressed in tight enough to avoid high pressure gas escaping!

How some vibrating media would get in is a pretty much the most ridiculous.............

Ah #### it. I'm done.

 

[curtmg]

And I'm pretty sure no tumbling media got into my loaded cartridges.

Where would it get in?

The primer and bullet are pressed in tight enough to avoid high pressure gas escaping!

How some vibrating media would get in is a pretty much the most ridiculous.............

Ah f**k it. I'm done.

Take off your genius hat, and try the sense of humor hat. Perhaps then it will all be clear.

 

[irniff]

I dont have a scientific explanation but a member at our shooting range fire 2 rounds

hard time to open the bolt ....

there were ammunition from previous years, they were install in a leather case for hunting

they were very dark , they were reaload ammunitions , he put them in the thumbler
until they come clean

there must be a reason why the pressure went up like this, we conclude it was beacause
they were put in the thumbler

 

[old enfields]

As part of the manufacturing process, the fresh powder is tumbled for hours. The powder does not break or crumble.

The graphite is not a retardent. It s there to dissapate static electricity.

The retardent coating is something like DNT (not to be confused with his first cousin, TNT) and is adsorbed into the grain and cannot be rubbed off.

As far as I know Ganderite used to make amunition for a living. I am going with his answer.

 

[acrashb]

there were ammunition from previous years
they were very dark
they were reaload ammunitions

Or it could be because it was really old reloads.

I've seen at least one experiment with some rounds tumbled and some not, and no difference across a chronograph. It doesn't hurt the powder.

 

[Papaclaude]

An earlier thread on tumbling primed brass brought the following comment:



OK, being naturally inquisitive, I did a bit of an experiment. I loaded a Federal .270 Winchester case with a live primer and a flat-based bullet. The charge was 50 gr of 4350, which I selected because a) its tubular shape would make it easier to see if any grains had broken apart and b) I had a bunch to spare. I chose 50 gr as that allowed a little room for the propellant grains to bounce around.

Before loading, I went over the lot with a magnifying glass. There were no broken or partial grains; all of them, ie, were intact when loaded.

The completed round was put in a Frankford Arsenal Quick-N-EZ tumbler for eight hours, along with a handful of empty brass and Lyman Tufnut media with no additional additives.

At the end of eight hours, I pulled it apart and again examined the propellant. Result - no broken grains. As in, nada, zilch - 100% of the propellant grains were intact. When poured out onto a white plate for examination, there was no evidence of any very fine powder of the sort that might have resulted from the corners of the grains being knocked off.

Now this of course is hardly a proper scientific experiment. To do that, one would have to test different propellants and different charge weights in different types of tumblers. All I have proved is that this one round, using one propellant type, did not suffer any perceptible damage to the propellant. Still, it's indicative.

For what it's worth...

Maybe that myth is like the pointed bullets in tube mags myth - doesn't stand up to scrutiny, or could it be that old powders weren't as resistant?