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Old July 11, 2011, 07:29 PM   #1
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Ultrasonic vs tumble - which is cleaner?

Yeah, this seems to be one of those topics that's been beat to death, but I bring forth something as rare as common sense in Washington - actual data.

Let me start by saying this isn't a plug for or against any particular method of cleaning. It's simply data I generated to satisfy my own curiosity, and I thought I'd pass it on.

Santa Claus brought me an ultrasonic cleaner this Christmas past, and I quickly noticed that, by comparison, my tumbled brass, despite being nice and shiny, wasn't as clean. Using ultrasonically cleaned brass, my wheelgun stayed noticeably cleaner, and was less likely to hiccup during reloads at IDPA & USPSA matches.

I just bought a new-to-me G17 as found about 350 pieces of once-fired Federal 9mm brass I had been hanging onto, so felt it was a good time to test the 2 cleaning procedures.

All the brass was de-primed using a Lee universal de-priming die, then randomly divided into 2 groups (A & B) of 170 pieces. From each group, I weighed 10 pieces 8 times and determined the average and standard deviation.

The brass in Group A was then cleaned in my ultrasonic cleaner, rinsed, dried and re-weighed:

Group A, 10 cases, ultrasonically-cleaned

initial weight: 37.14 ± 0.54 grams
weight after ultrasonic cleaning: 37.15 ± 0.63

The brass is very clean at this point, but that it didn't get lighter suggests the weight of the crud is actually pretty low. At this point, I'm predicting that tumbling brass will actually increase the weight if it's dirtier than ultrasonically-cleaned brass.

Group B, 10 cases, tumbling, followed by ultrasonic cleaning

initial weight: 37.24 ± 0.50 grams
weight after tumbling (2.5 hrs in walnut media): 37.67 ± 0.71
weight after ultrasonically cleaning after tumbling: 37.14 ± 0.51 grams

Sure enough, tumbled brass got heavier by 0.43 grams/10 cases. After tumbling, I ultrasonically-cleaned, dried and weighed the brass and found it now weighed what the ultrasonically-cleaned brass in group A weighed (37.14 ± 0.51). The math indicates that tumbling leaves (37.67 - 37.14 =) 0.53 grams of residue per 10 cases. Convert this to grains, and it indicates that 9mm brass accumulates 3.5 grains of residue per 75 cases. IOW, during the course of a monthly IDPA match (75 rounds), the crud that gets pushed through my gun is equivalent to the entire powder load in a 76th round. And assuming surface is proportional to case weight, .45acp brass, for example would accumulate 45% more tumbling residue (10 .45acp cases = 53.82 grams).

To really drive this home, I ultra-soncally cleaned brass from both groups A & B, then collected the soapy water afterward. As you can see below, the wash medium from tumbled brass is considerably dirtier than the medium from brass that had been previously ultrasonically-cleaned.

MrBorland is offline  

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