Tumbling loaded ammo THE TEST

[CPTMurdoc30]

Disclaimer: Please do not try this at home. I can not be held responsible for any loss of equipment or life or anything that happens from you trying this experiment.

From time to time we get into a debate about whether it is going to affect your hand loads if you tumble them after they are loaded. We normally get two polar opposites on this one. First is sometimes called “fradey cats”, because like me we head the powder manufactures warning and do not tumble our loaded ammo. Most of the time we use the excuse they are the experts not me. Second are the “commandos” who do not heed the warning of the PhD lab coats working at the powder manufactures and tumble their loaded ammo and say it does nothing, some have even claimed better accuracy.

the components.



So I am going to try and put this to a rest. I have loaded 12 308 Win cases with 4 different powders using Remington cases Winchester WLR primers and Hornady 168gr A-max bullets. The powders I used are a short cut extruded powder (Benchmark) a Ball powder (WIN 748) a medium length extruded powder (IMR 4895) and a Long Extruded Powder (IMR 4350). The weights of each load was taken from the Sierra “5th Edition Rifle and Pistol Manual of Reloading Data” and are all in the middle of the load range filling the case to right around to the bottom of the shoulder. For the test I loaded 3 each with the same powder charge as measured on a Lyman M-5 (RCBS 10-10) scale.
Powder charges are seen in the picture below. I choose these powder for a few reasons 1. It is what I have on hand. 2. I cover just about all rifle powders on the market with ball, short, medium, and long Extruded powders. 3. I wanted to see if one type of powder was more susceptible to damage than another.

• Winchester 748 43.5gr

• Hodgdon Benchmark 39.0 gr

• IMR 4895 40.0 gr

• IMR 4350 46.0 gr

NOTE: Powder seen in photo above is for size and color reference, and it is not for amount of powder used in each load.

The test started at 12:22am Tuesday, July 01, 2008 First check will be Tuesday, July 01, 2008 at 08:22am for a run time of exactly 8 hours. This check will involve using a kinetic bullet puller and examining the powder in each case with picture documentation. The same powder will then be placed back into the case and the bullet reseated and placed back into the tumbler for another 8 hours. After 16 total hours of tumble time in a Midway USA/ Frankfort Arsenal vibratory case cleaner loaded with corn cob media the loaded ammo will be removed from the tumbler. All rounds will again be pulled part for inspection and photographic documentation. After that I will neck size all cases (For safety reasons) and reload all the powder back into the case for test firing from a sandbag rest at 100 yards. I will also load 3 more of each and set aside for accuracy results. I will also fire all rounds over a Shooting Chrony F1 Chronograph I will note all velocities and work up Extreme Spread and Standard Deviation using an Excel ballistics calc spread sheet.

Clock and ammo in Tumbler. Time 12:21AM Tuesday, July 2008.


NOTE: 12 loaded rounds in tumbler.

[snuffy]

Good! Better you than me AGAIN! I say again, because I did the same thing about 4 years ago, but with only 1 powder, R-19. In a 300 WSM I tumbled for 1-2-3-4-5 hours, taking 5 out at 1 hour intervals, then at 10 hours, and then at 15 hours, where I stopped the test. I could see no visible change in the powder, no dust or broken granules.

The came the shooting over my pact chrono, while shooting groups.

To make a long story shorter, THERE WAS NO DIFFERENCE, from beginning to the end.

[SL1]

CPTMurdoc30,

I think TexasSeaRay did a similar test with handgun rounds that he tumbled for WEEKS, and still got no differences.

Maybe you should try for MONTHS if you really want to see a difference.

Also, maybe a BIG rotating tumbler instead of a vibrating one MIGHTshow more effect. You know, the commercial 5 gallon drum size, where the ammo gets to drop a significant distance in each turn.

Finally, please do the statistics properly when looking for differences. In 3-round test groups, they would have to be BIG differences to be confident that they were real differences instead of just statistical fluctuations. We don't want any more "Urban Myths" created based on misinterpretation of statistical fluctuations.

You know what I mean. Please no:

"Tumbling for 10 hours increased mean velocity by 3%, which means that pressure must have increased by 6%, which means that this test showes that tumbling for a little over 2 days will increase pressures to proof-load range!"

Nor do we want:

"Tumbling for 10 hours decreased group size by 35%, so tumbling for 50 hours should reduce group size by [1-(.65)^5 = ] 88%!"

So, please make sure that the any differences you find have 95% statistical confidence that they are not casued simply by statistically insignificant variations in your results. No sense sending the "fraidy cats" nor the bench rest shoots into another tizzy.

SL1

[CPTMurdoc30]

After 8 hours in the tumbler.
Pulled all bullets and inspected powder in pan and back of bullet. The Benchmark shows a very slight amount of “dust” on the back of the bullet. The Winchester 748 showed the least amount of “Dust” on the back of the bullet. The IMR 4895 shows slightly more “Dust” on the back of the bullet along with visible dust in the powder pan. The IMR 4350 showed the highest amount of “Dust” on the back of the bullet.

The brass used was once fired and had been cleaned twice before this loading. The “Dust” I am sure is from the powder and not the case as the Benchmark “Dust” was the same green color powder. There for I am going to say while it is not a significant amount of “Dust” and I seen not one single broken kernel the fact remains that something is happening to powder in a tumble. Weather it is able to be seen with the naked eye cannot be determined at this time. I would have to caution anyone from tumbling loaded ammo. I for one will stick to the not tumbling loaded ammo. As I can see with my own eyes that something is happening to the powder.

Also I noted damage to about 25% of the polymer tips of the Hornady A-max bullets. Ammo went back into the tumbler for another 8 hours.

08:22 hours time to remove loaded ammo.


Benchmark

[CPTMurdoc30]

IMR 4895






Win 748




Missed one Win 748 picture.

[CPTMurdoc30]

IMR 4350







Bullet with powder Dust on it.

[snuffy]

The brass used was once fired and had been cleaned twice before this loading. The “Dust” I am sure is from the powder and not the case as the Benchmark “Dust” was the same green color powder.

The "dust" you saw/found was from the carbon left from the original firing. The ONLY way to do this test is with new, virgin cases.

In my test, my cases were new Norma cases. Another guy on the AR forum also was doing a test at the same time I was. He did the same thing as you, used a previously fired case to tumble loaded. He got a bunch of "dust", concluded that it was carbon from the previous load. He then repeated the test with new cases. Then the powder came out clean, no dust.

This is powder from the shells from that fella on AR, showing the difference between a fired case and a virgin case.



Here's R-19 powder after being tumbled for 15 hours in 300 WSM cases. Note the absence of any "dust".



Also, showing your results in a red powder cup shows no detail. Spread it out on white paper, it'll show up much better.

[snuffy]

Also, here's the original tests done by me. Look for post #18. I don't think that link to the AR thread works anymore. Saeed re-formatted his forum several times since that thread was on there.

Wrong answer. That original link does work!
http://forums.accuratereloading.com/...43/m/602103723

http://www.thehighroad.org/showthread.php?t=156750

[Shoney]

CPTMurdoc30 wrote:
we heard the powder manufactures warning and do not tumble our loaded ammo. Most of the time we use the excuse they are the experts not me.

Is this another urban myth of a friend of a friend said this heresy eeeeerrrrrrrrrrrrr I meant to say hearsay?
Where is there documentation of this?
I have never seen any.


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