Hello all,
         A recent case in the lab has brought up the question of Chamber Marks alone as proof of "fired in" status of a shell casing, as opposed to just "chambered and extracted in" status.

         We've discussed the possibility of doing a study to see if we can conclusively determine "fired in" status based solely on chamber marks.  I would like to ask if anyone here has seen or heard of such a study being done, or published before?  If so, could you please direct me to it?  I'd like to try and collect as much information that's been done about chamber marks as I can before we get too far ahead of ourselves.

         Thanks in advance for any help you can give,

Ken

Here's an article that may be of some assistance.

As a new graduate of the "Criteria for Identification Workshop", those great looking "fireformed" marks look a lot like sub-class characteristics.

:D

Sorry, didn't mean to get the topic off track.  Just ignor that prior post   :)

Scott, it may be too late for "de-programming" to be effective with you. :roll:

A few years ago Caryn Tucker from the Illinois State Police-Chicago Lab did some research for her Masters on consecutively made chambers from Hi-Point. I don't believe her study was ever published. I did take the blind test she put together using the consecutively made chambers....and successfully completed it. I am not certain if she has expanded her study or not. You may want to call her to discuss your topic-312-433-8000.

I am currently working on a research project regarding chamber identification.  I am working with ten consecutively manufactured chambers from Hi-Point and Ruger, and am trying to obtain chambers from Keltec also.  I began this study as part of my research for my thesis, and am now expanding this.  I have not published this work yet.  You can call me to discuss, 312 433-8000x2226

Marking originated from errosion of barrel or chamber is unique in nature, and it is possible to identify using these markings. However reproducibility of such marking is usually not so high than Bob's 22 rimfire case example.

Here are comparison photos on the mouth of  two cartridge cases of Tokarev.
Tokarev cartridge uses Berdan primer and is non-relodable. I encountered such deep chamber mark for the first time after examining more than 1,900 Tokarev test fired cartridges.

I do not think such deep chamber mark impressed only by chambering and extracting procedure.
The markings are from open case, and I have not confired that.

Thanks to Bob for attaching his article on the rimfire cartridge cases and chamber marks.

From experience as a gunsmith and firearms examiner I have found that the greatest area for chamber marking on rimfire cartridges and particularly fired cartridge cases is where the firing pin aligns with the chamber mouth. When rimfire firearms are 'dry fired' their firing pin nose can impact with the barrel's chamber mouth causing indentation and burring damage. Some firearms experience repeated 'dry firing' and display considerable damage in this region which is transposed onto the fire form cartridge case.