Shooters Forum banner

1 - 9 of 9 Posts

·
Premium Member
Joined
·
15,427 Posts
Discussion Starter · #1 ·
Many years ago, I took a peek through a stereo zoom microscope at a worn gun part. It opened a whole new world and shortly afterwards I acquired a very high quality stereo microscope and have gathered the bells, whistles, attachments and accessories that make it a very valuable tool in all phases of gun investigations and my main vision for engraving. Stereo microscopes tend to accumulate when ebay sells them SO cheap! .... or maybe they multiply when left alone.:confused:

Last month, I sold a couple of 'surplus' stereo microscopes and bought a tool I've always wanted but only occasionally actually need and have been out of reach economically for the last 15 years. A forensics-ready comparison microscope loses very little value and scopes made in the '40s still sell for more than I want to pay. Such a 'scope with the proper holders, positioners and lights commonly sell for more than $2k, used (up to $40K new). Then a surplus dealer misspelled 'comparison' and started the auction very low. It sat for nine days and 23 hours on ebay with (evidently) only me watching it. Shipping was nearly equal to the selling price but still was one GREAT bargain.
I'll post pictures as soon as I get enough bench space to put it on and set up right. The very first test was to match up fired cases shot in three different .41 Mags looking at only the face of the fired primers. Less than ten seconds each was needed to make a perfect one factor match and lining up two cases to look like one very unique primer is downright fun!
It's not a bad thing that my bullet catcher is a natural hot springs-fed concrete pool seven feet deep, either. I've always been curious how defects in the crown affects rifling analysis and I'm about to find out by shooting, swimming and looking.

This is a mid-range 'scope that retails just over $20k. Labs that use this equipment upgrade every ten years or so. Ebay exposes them to the world.
 

Attachments

·
Premium Member
Joined
·
15,427 Posts
Discussion Starter · #4 ·
I could show you my Russian periscope artillery binoculars.... ebay is dangerous to a debit card!
 

·
The Shadow (Moderator)
Joined
·
8,369 Posts
It's not a bad thing that my bullet catcher is a natural hot springs-fed concrete pool seven feet deep, either. I've always been curious how defects in the crown affects rifling analysis and I'm about to find out by shooting, swimming and looking.
Not sure how fast the 41 is moving, but you may have to fire it underwater, if you don't want the bullet to crumble.
A few of us bozos did the "pool water trap" a few years ago, can be very hard on super-sonic bullets.
Assuming a FMJ type bullet, pistols tend to not frag; but they can definitely get contorted as they tumble and slow.

Let us know how she goes!

Cheers
 

·
Premium Member
Joined
·
15,427 Posts
Discussion Starter · #6 ·
I ran extensive visual test of bullet expansion in a bigger pool with scuba gear and a girl friend that didn't mind getting wet by shooting off the diving board about 20 years ago. FASCINATING study that should have been recorded--22LR to .375 H&H with a bunch of varmint calibers and bullets tested over several days. (one reason I have shot and still have thousands of Ballistic Tips). The one gun that surprised me the most was my SA .41 Mag shooting 255 gr hard cast at 1080fps. The bullet went straight down, 7' 2" and hit the concrete bottom with a loud CRACK. The nose of the LBT was flattened enough to convince me it could be a gator killer at five feet deep. Factory SP and HP handloads acted the same as any other with 4 feet of rapid penetration and then a falling bullet to the bottom.
Water does weird things--- I tested an SKS with hardball ammo and with a little practice could shoot a target floating on the pool surface and have the bullet land on the sidewalk on the other side, bent like a banana. FMJs are dangerous to be in the water with.
 

·
The Troll Whisperer (Moderator)
Joined
·
23,886 Posts
gwpercle - a little attempt at humor. Evidently, some don't share in my sense of it.
 

·
Registered
Joined
·
81 Posts
Hi Jack,
Your new tool is intresting to me. When you update with results, could you post a short blurb on how & why you use it with some pix of what it shows & what it means? I know you sorta promised this in your opener, just wanna encourage you!
 

·
Premium Member
Joined
·
15,427 Posts
Discussion Starter · #9 ·
Thanks for that. I'm waiting on the calibration instrument right now, but my use is limited to legal work and personal curiosity. The legal work mostly concerns primer marks---Does a primer look different if the trigger wasn't pulled but the gun obviously fired? The comparison microscope holds two fired cartridges. The micrometer adjustable stages align each case dead center its respective lens. The binocular eyepieces can, by the turn of a knob, move a black dividing line right or left so the viewer is looking at the right case or the left case in a full view, or, both cases at the same time on a split screen. That split screen can be brought together so half of each case is joined in the middle optically. The case can be rotated so the striations of the recoil shield, firing pin bushing of bolt/breech face are seen in relief. Definition is gained by oblique light, polarized light, or filters of one kind or other and the machining marks of the parts are seen imprinted on the primer. It only takes a glance to see what matches and what doesn't. Extractor, ejector, chamber markings, and the firing pin indentations are all points of identification in cartridge cases. Of course Hollyweird focuses on the bullet and matching rifling marks, but many times the bullet is not available or a bullet has to be matched to one gun and a fired case.
I also have a tool maker's microscope that measures vertical distance optically to four digits. The combination of the two microscopes allows me to say one gun shot two cartridges that are different in impact and explain why.
I'm NOT a tool marks examiner so can't testify in State Courts, but I can save a lawyer thousands of $$ in figuring out exactly how good his case is before throwing gold bricks at it.

Hypothetical-- 'My SA .44 fell and hit the edge of the concrete step and blew most of my leg off.' With the fired cartridge and an exemplar fired cartridge from that gun, I can say to a reasonable degree of certainty if the gun fired by falling without having to fly across the country to look at it.

May years ago I worked for the defense of a guy accused of murder. Part of the evidence against him was three fired .22 LR cases traced to a Ruger Mark I, which he owned one of. The evidence cases were Dominion-made and showed a unique 'ding' on the firing pin nose. The prosecutor said the firing pin had been replaced. The defense hired two guys with metal detectors and retrieved nearly 3000 fired cases from the defendant's back yard range. I went through them one by one looking for the odd firing pin mark and Dominion cases. There were a hundred or so Dominions but none of the fired cases matched the murder weapon's firing pin mark.
(the cops are obligated to re-check my results and their findings are exculpatory and powerful.)

I'm anxious for pictures too. Soon I hope.
 
  • Like
Reactions: shawlerbrook
1 - 9 of 9 Posts
Top