Topic: Lead deposition in an A-TEC CMM4(6) Suppressor

[Brandon Bertolli]

I bought an A-TEC CMM4 suppressor configured with 6 baffles. This is a rimfire suppressor currently on my SIG522. I've been weighing it and X-raying it after every 500 rounds (with no cleaning).
Part 1 of my observations can be found here:


http://tinyurl.com/j4wrw83


Here are the latest X-rays with round count in red and weight in yellow:





I can't explain the weight fluctuation at present. The scale I use is only accurate to within 1g, so I am going to get another one which is accurate to 0,1g and double weigh the suppressor in future.


This A-TEC aluminium suppressor is easy to X-ray.
I have recently bought my 4th suppressor which is an ASE Utra all-steel model, and I have found it very difficult to get decent images on that one. Considerable changes to X-ray technique and exposure are required, but the control radiographs I acquired on Thursday look promising.


I will be doing the same experiment with the ASE Utra...

[Charles Clow]

Brandon,

What question are you trying to prove or disprove with this research?

Regards,

CMC

[Brandon Bertolli]

Hi Charles


I want to trace the deposition of lead over time. The question is two-fold:


1) What is the maximum lead (by weight) that this suppressor can accumulate over normal use without cleaning?
2) At what point (if any) does performance degrade. I am looking for obvious changes in group sizes and sound.


It might well be that there is a natural equilibrium between the deposition of lead and the ejection of lead from the suppressor.


Once I have repeated this experiment with a bunch of different suppressors and ammunition I may be able to offer some interesting comparisons, some of which may have forensic value.

[Aaron Brudenell]

Here's a single slide from a presentation showing similar results only with 3 different suppressors (the 3rd is made from different material).

[Brandon Bertolli]

Thanks Aaron, good to see I'm not the only one X-raying these suppressors.


With regards to the steel suppressor, it requires a markedly different X-ray exposure and the use of an anti-scatter grid to get a reasonable image.
The A-TEC suppressor is all aluminium and can be X-rayed on a direct detector at 75kV and 2mAs.


My ASE Utra is all steel (even the baffles) and has a double tube design. It requires an anti-scatter grid and an exposure of 121kV and 1mAs.
Here it is being X-rayed alongside an aluminium step wedge as a density reference:





And here are the radiographs. Note that because of the baffle design I take three exposures with the suppressor rotated at different angles so as to get visualisation of all the spaces where lead can accumulate (which you don't have to do with the aluminium suppressor):











If you X-ray the aluminium suppressor with a technique for a steel suppressor, the aluminium one is burned out on the image:





And if you X-ray a steel suppressor with a technique for an aluminium suppressor, the steel suppressor is under exposed:





Under the hood of the X-ray receptor:





The yellow surface is the detector and ionisation chamber combination. The black tray being slid out (to place on top of the detector) is an anti-scatter grid. If it is a focussed grid such as the one above, it will have a fixed working distance. In my case it is 115cm...

[Aaron Brudenell]

Very cool and informative!  I only do this occasionally when I'm trying to get a look inside a casework can and I bug my friends at the ME's office to run the equipment (only thing I learned was the "skull" setting seems to do a good job).  A lot of the homemade or primitive designs have interesting packing material as well that can show up.  One in particular had all of the packing disks forced to the muzzle end of the suppressor due to use.

[Brandon Bertolli]

Up to 4000 rounds now:

[Brandon Bertolli]

Part 2 here:


http://tinyurl.com/jn875ps