1" thick plexiglas vs. S&W 686-1

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One of the many things we work on at work are scanner-scales, they're the devices in supermarket check out lanes that scan and weigh grocery items.

Some of the older models used thick plexiglas windows, about 1" thick, part of our refurb process is to replace any windows with scratches that compromise scan reliability.

So, basically, I have two 1" thick plexi targets, they're roughly 4x5" in size, I've shot them before, and they basically shrugged off .22LR, it just left a smear, a .22 Mag hollow point left a dimple about the diameter of an un expanded .45 ACP, and 5.56/.223? Well, let's just say I'm still finding pieces from the first one I shot about 6 months ago, those rounds completely demolished it.

So, a little more research is in order, try a few more magnums on one, a FMJ, a lead free, and a ballistic tip, see if I can capture any shock waves inside the plexi...

The second one? That'll be for my S&W 686-1 .357 Mag, I'm thinking starting with a .38 lead wadcutter, then a .38 FMJ, a .38 hollow point, then a soft point .357, and if any remains, a Gold Dot hollow point .357...

No point in trying LR on the plexi, I know it won't be able to damage the window...

So, per my nephew's request, we tried the .38 Spl first...

145 grain full wadcutter left a faint scar and lead smear
155 grain FMJ left a shallow crater
135 grain Gold Dot hollowpoint left a slightly deeper and wider crater

Then the .357;
155 grain left a deep crater
165 grain (IIRC) PMC soft point blew it cleanly in half!

We shot a different location for each shot, the .357 SP was the coup de grace, it decimated the plexi window.

1" thick plexi seems to be able to withstand up to .38 Spl, starts to fail with a .357 HP, and a .357 SP utterly destroys it.
 
I'm curious, do the grocery store clerks really thunk down the goods so hard that you need 1" thick Plexiglas on the scanners?
 
I'm kinda thinking its Lexan, not Plexiglas.

Lexan is bullet proof and behaves as you described when shot.

Plexiglas not so much.

rc
 
Lexan is polycarbonate, Plexyglass is PMMA. Based on the poor performance and the application* the OP is probably correct (PMMA is very strong but brittle under impact).

*-PMMA can be made very scratch resistant (It's a standard glass alternative in headlight housings and airplane windows). Polycarbonate scratches easily.

Mike
 
I agree with Arizona Mike. Lexan is “Softer” than Plexiglas and will absorb an impact. Plexiglas is more brittle and prone to shattering upon impact. That is probably why the market scanners use such a thick Plexiglas, to prevent it from shattering by shear mass. And that’s why banks, check chasing places, etc. use Lexan for their “Bandit barriers” that will absorb a bullets impact and stop it without allowing full penetration and why Lexan is used for racecar windshields.
 
Acrylic/plexiglas doesn't provide much of a barrier. I've had 5.56mm blow through a 4" thick round slab I had, leaving a large crater and serious spalling.

Generic lexan is a decent barrier. I had some 1/2" pieces that stopped 9mm, .45ACP, and #00 12ga cold. It bulges the backside but not even close to penetrating. .357mag punched clean through through. It stretches instead of cracking or shattering, so you don't get catastrophic failure or spalling.
 
My 2 cents on the subject. Plexiglass is a cheep alternative for replacing windows and the like. Lexan is just a higher grade of plexiglass of which is a little stronger and has better forming capabilities than plexiglass. Now cast acrylic is the Strongest of the 3. they are all pretty much the same thing just different chemical compositions. I worked in cast acrylic manufacturing for 10 yrs. Our biggest customer was the US Gov. they use it for jet canopy's Apache window panels and the tank periscopes on the new tanks this was back in the eighties and talk about bullet proof we made **** a 1/4" and 1/2" that would take just about anything you could shoot at it.Even a M16 on full auto Brought in from Wright Patterson Air force Base I was in charge of all inspection and testing and shipping for the Gov. line. Twiki what you call Bandit barriers is Actually Cast acrylic. Oh BTW Lexan is just a company name Not a grade of Plastic


Dawg
 
Lexan is a brand name for poycarbonate (PC). It is not "plexiglass", which is also just a brand name for acrylic. PC is stronger, and is used for high impact non-spalling applications from electronic housing to bullet-resistant glass. If you are typing on a keyboard, that is PC you are tapping on. It is rated for 10 million "strikes" without cracking or failing. Acrylic wouldn't last more than a few hundred strikes.

PC is stronger, although it scratches, Acrylic can be polished easily but is softer and will crack. The reason why acrylic is often used is because it is much cheaper than PC.

KFC with PC shielding. It may have a film coating of some sort to prevent scratching.
24f342dac264e7b30479ff24033a444e_view.jpg
 
A local machine shop gave me a disk of polycarb that was cut out of a bank window for an armored intercom speaker. They had already shot it with a .38 special 158 gr. LRN (gray smear) and 9mm 115 gr FMJ (buried until base of bullet was just flush). I told them I wanted to borrow it for a few days and took it out with my CZ-52 loaded with some 7.62x25mm hot Chinese ball.

WOW! I don't think the bullet even slowed down, judging from the penetration through the wood stump supporting the plastic.

The guys in the shop were quite impressed. Luckily, 7.62x25mm is not a popular "street" caliber, and is not often seen in criminal activity.
 
Lexan

Worked on an armored truck for a few years prior to being an LEO.

The Lexan that covered the windows was TOUGH,and I got the chance to shoot it with a .357 a few times.

the Lexan did stop that round,and I have a piece of that still in my possession.

But it will not stop rifle rounds,in any caliber.

Very heavy and very expensive.
 
Lexan (polycarbonate) can easily be coated with a hard, scratch resistant coating. Motorcycle windshields made by National Cycle, Inc. does this to their full line of after market motorcycle windshields. Here is a link to their process:

http://www.nationalcycle.com/WhyBuy/chapter4.html

Also, modern polycarbonates have been formulated to be "water clear" and not the bluish tint of the older polymers.

Dan
 
If you are typing on a keyboard, that is PC you are tapping on.
I thought most electronics shells were ABS plastic? Fancy keyboards I can see being polycarbonate (ironically enough, like the one I'm using at the moment). Only reason I know is that ABS gives off evil fumes when burned but PC not as much, so it is slightly more desirous in enclosed areas (nylon's even better, but is much wimpier and melts easily)

TCB
 
I like the test, but am not sure of the validity of the results. While the material may have been shot in multiple different places, that does not mean that the prior impacts did not compromise the overall structure, if just through microfracturing.

.357 may defeat it, or may not, not on a first shot basis. We don't know that after being shot up that the material would not have failed with .38 spl again.

Looking at the images on photobucket, the shots may have been in different places, but the damaged done by some shots overlapped with some prior shots. Basically, it looks like the center of the material was overloaded with impacts and summarily compromised as a result.
 
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