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Old November 17, 2008, 09:26 PM   #1
GlockJockey
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Polymer Framed Handguns - Frame Flex??

Folks;

I'm looking for information on frame flex - sometimes referred to as the Modulus of Elasticity - as it relates to polymer framed handguns. I've heard bits and pieces about how a polymer framed handgun frame can flex slightly under recoil, but I'm wondering if there's been any sort of definitive study done to determine how it all happens.

Also, does having a light source under the barrel affect the flex of such a frame, and maybe cause failures to feed? I've had a good dig around (even in the old-fashioned realms of ink and paper) but can't seem to locate anything.

If anyone has any information on where to find any sort of scientific treatment of this, I'd love to hear it.

Cheers!
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Old November 17, 2008, 09:55 PM   #2
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I suspect the most reliable and autoritative information would come from ATF, possibly FBI and large Law Enforcement agencies, the manufacturers of the material and the frame manufacturers.
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Old November 18, 2008, 12:02 AM   #3
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totaly non-scientific

I'm no materials scientist and I can only occasionally say modulus of elasticity without either stuttering or drooling but I have witnessed a fair amount of frame flex evidence on one particular brand of polymer pistol.

Open up most any .40S&W Glock and take a look at the bottom of the slide, between the rails just about even with the slide stop notch. I have yet to see one without some damage caused by the slide and locking block slapping together.

As for failures caused by tac lights, yes they can. Or at least they used to. The first Glocks to come with light rails were notoriously finicky, especially with some of the heavier Surefire lights. It was bad enough that Surefire sold a rail that you had to attach to the rail so that the light wouldn't cause failures to feed. From what I recall, Glock never publicly discussed the problem but I think that they made some substantial changes to the frame to address the issue.

My current glock (KSRXXX) has a beautiful pignose and has never had a failure due to the weight of a light. I don't recall any of the first light rail Glocks having pig noses.

By contrast, the HK USP40 I shot for 5yrs never once seemed to care that there was a light attached nor did it show any sign of wear that could be linked to frame flex.
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Old November 18, 2008, 12:05 PM   #4
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All pistols flex under recoil; it doesn't matter if it's an all steel 1911 or a Glock. Some will flex more (e.g., non-reinforced polymer a la Glock).

I recall reading of light attachments and failure to feed with Glock some years ago. I'm not sure what the root cause was but I assume it had something to do with the flex modes due to having a relatively large mass hung on the dust cover.

This was over 8 years ago and much has changed: the lights weigh less and there has been modifications to the specs of Glock frames.

Hope this helps.
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Old November 18, 2008, 12:32 PM   #5
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All pistols flex under recoil; it doesn't matter if it's an all steel 1911 or a Glock. Some will flex more (e.g., non-reinforced polymer a la Glock).
beat me to it
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Old November 18, 2008, 04:43 PM   #6
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Thanks all.

I've been casting around on this topic, and while there's a little bit of materials science (which is wayyyy above my head) on the subject, it would seem that the only people who have done any testing on the topic are the firearms manufacturers themselves - and they're not sharing.

(Fair enough, I suppose - apart from liability issues, it might give the competition an edge.)

Thanks for the replies thus far. I don't expect that I'll find much in the way of hard data, but the above has been useful. Much appreciated.
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Old November 18, 2008, 06:08 PM   #7
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Flex-fire and accuracy

No gun could flex like the pig-nose haters say a Glock does and still be so accurate. My G-30 (# LEOXXX, ain't that a hoot!?) is more accurate than my G-21s, maybe due to the shorter moment of inertia not flexing the frame as much. I took my brand new, NIB G-30 to the range to break it in. I was shooting fmj off-hand at 35 yd., Shoot'n'see 6" tgts. Every shot was orange. Spotter was a guy in the next pavillion, and he couldn't believe it. I handed the G to him, and said, "These sights seem to be right on. Empty it at the tgt. You won't need your spotter." And he did as well as I did. If there is any flex, the frame sure does make a fast recovery!! Why not try to inquire of Gaston G as to his flexing findings? Maybe I will. Glock's full-autos in 9x19mm are unmatched for defense,i f you can get one, or make one. Can you imagine a 1911-style 9x19mm trying to fire full-auto!?! And if the Glocks "don't point right, shoot to natural point-of-aim, feel right, aim right" then why not try using your sights? All handguns have them.
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Old November 18, 2008, 06:17 PM   #8
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This video shows a Glock a flexin pretty clearly.
http://www.youtube.com/watch?v=B-ToCK4C7ig
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Old November 18, 2008, 06:24 PM   #9
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Flex?

It's pretty plain that there is no flex visible. But, remember that the early Gs had only the 1 pin above the trigger-group. Later there are 2. Gotta be some reasons!
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Old November 18, 2008, 07:33 PM   #10
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If it wasn't flexing, what was it? The whole dust cover was visibly vibrating under recoil.
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Old November 18, 2008, 10:47 PM   #11
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Steel is for guns. Plastic is for toys.
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Old November 18, 2008, 11:04 PM   #12
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Amen.
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Old November 19, 2008, 05:39 AM   #13
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This might be a good one to suggest to the guys at Time Warp on the Discovery Channel.

http://dsc.discovery.com/tv/time-warp/time-warp.html
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Old November 19, 2008, 09:10 AM   #14
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OF course, poly-framed pistols flex more than steel-framed pistols. One of the benefits of that flexing is the absorption of recoil pulse. Yes, some of the earliest Glocks with rails did have problems with lights attached. That's been corrected.

I guess my question to the OP would be, "If you had all of that data, the math of which is probably above your head, as you admitted, what would you do with that data?"

The old "steel is for firearms, plastic is for toys" mantra is pre-adolescent silliness or just plain ol' ignorance.
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Old November 19, 2008, 10:48 AM   #15
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"The old "steel is for firearms, plastic is for toys" mantra is pre-adolescent silliness or just plain ol' ignorance."

Whatever floats your boat. Have you shot many "polymer" framed revolvers lately?
Plastic is a cheap way to provide a working firearm at a much inflated price, why would any dishonest manufacturer want to mill steel? If on the other hand you can, over time, convince the public that plastic is "better" than steel you can make huge amounts of money fast. I'm waiting for them to convince people that a plastic barrel and slide are better too.

I make parts for industry out of steel, aluminum, copper, all the metals, and yes, plastic. I have seen the many ways parts made from differing engineering materials find their way into the scrappers bins. I've replaced steel where aluminum has worn away or fractured. Plastics are more often used as disposable or consumable parts like bushings. You may find plastic buttons in the controls of a machine but very seldom in the inner workings where the hard stuff is done.
Sometime I replace a bronze bushing with UHMW or some other plastic, if there is enough area available to support the forces. Plastic deforms excessively if it isn't supported well. In the right situation a plastic bushing will wear out a steel shaft.

If I design a machine there is no plastic in it. If there is any aluminum in it it has steel slides running against bronze ways. Manufacturers typically design for a planned lifetime. John Browning made his designs to last for unlimited time, anything that did wear out could be replaced.

I'm just ignorant and juvenile about plastic I guess.
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Old November 19, 2008, 10:57 AM   #16
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Quote:
You may find plastic buttons in the controls of a machine but very seldom in the inner workings where the hard stuff is done.
Which is where you find it in a gun also.


Quote:
John Browning made his designs to last for unlimited time, anything that did wear out could be replaced.
Can you give an example of a polymer gun that "wore out"?

The plastic that's used in toys is for toys. Saying the word "plastic" and pretending it's all the same is like saying "metal" and pretending it's all the same. There are plastics that are EXTREMELY strong while still being light-weight and many of them are used to make guns.
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Old November 19, 2008, 12:01 PM   #17
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Ferrous-polymer

Those who post "plastic" in this thread are usually bigoted (including me). The 1911-style is pure genius, and has been so for 100 years, never to be supplanted. The name "Glock" stands for "the search for 'Perfection'...", and BTW, 80% of my G-21, by weight, is steel, and 00% is 'plastic'. Amen.
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Old November 19, 2008, 01:23 PM   #18
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Seems a matter of definitions.

To quote a gun bible: "" Let's look at Steindler's definition: "Dust Cover: a sliding, easily removable sheet metal device on some military rifles. Installed to protect the bolt from rain, dust and other foreign matter."

How, I have wondered, did some nitwit apply this term to the front of an auto pistol frame? Someone in military ordnance, perhaps? Not so. I dug out an original (1942) TM 9-1295, and looked at all the specs and illustrations. The only reference is to the entire frame as the "receiver." Anyway, I refuse to call the front of the frame a "dust cover."

COPYRIGHT 2005 Publishers' Development Corporation
COPYRIGHT 2005 Gale Group ""

So if the front few inches of the "frame" is a "dust-cover", where is it that I should look for the flexing? In all seriousness, I can't see any flex in that very slow action shot. Not to troll or quibble, I just don't detect it. Where is it happening? Sincere thanks.
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Old November 19, 2008, 05:17 PM   #19
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The projection of the frame in front of the trigger guard flexes during the video. At one or two points in the video you can actually see it vibrating slightly.
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Old November 19, 2008, 05:53 PM   #20
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I see we should never ever mention Glock and plastic in the same sentence. We need to remember that since it is used in the frame of a Glock we need to call it a polymer. Polymer, Plastic, Tomato, Tomatoe whatever makes it sound better is key, but make no mistake that frame on modern pistols is plastic no matter how much it makes you angry. I own a plastic Ruger P95 and yes I love it.
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Old November 19, 2008, 06:16 PM   #21
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Hey

I see what you call "frame-flex", just when the slide is affected by unlocking. But there is no larger clearance between slide and frame. IOW, no flex. This is at the initial movement of the slide. Then, when the slide is almost in full recoil, the recoil-spring guide-rod appears to move (it is allowed and is expected to move) and there is the illusion that the frame has again "flexed" when it has not. Sorry, Charlie.
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Old November 19, 2008, 06:20 PM   #22
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I'm not sure how you arrived at your personal set of criteria for what constitutes frame flex.

The point of the video is that the polymer does flex during the firing sequence as shown by the flexing/vibration of the dustcover.
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Old November 19, 2008, 06:46 PM   #23
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What is the material? Whenever I need a mechanical property (I am a mechanical engineer) I go to matweb. It may be listed here.

http://www.matweb.com/


I looked at wikipedia, which said glocks are made of high strength nylon. If that is true, matweb gives this:

http://www.matweb.com/search/DataShe...a829b05&ckck=1
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Old November 19, 2008, 07:06 PM   #24
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It's supposed to be a cast hybrid with a base of Nylon 6 and 2-3% carbon black added for UV resistance. I've also seen some information indicating that there may be some metal content (flakes or powder) added to make the frame more visible to X-Rays but I'm less sure of that information.
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Old November 21, 2008, 01:10 PM   #25
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"Can you give an example of a polymer gun that "wore out"?"

The only plastic gun I ever owned failed after less than 100 rounds, but it was poor engineering. There was a thread about the longevity of plastic a while ago. As an environmental pollutant plastics may last for centuries, but as a flexing stressed part that is not the case. I threw an ammo box out last night with a failure of the "miracle plastic hinge". :barf: I notice that when engineers want a plastic hinge to actually last they mold a regular swiveling hinge joint in.

"The plastic that's used in toys is for toys. Saying the word "plastic" and pretending it's all the same is like saying "metal" and pretending it's all the same. There are plastics that are EXTREMELY strong while still being light-weight and many of them are used to make guns."

Every kind of plastics are used in toys, don't kid yourself, any that aren't are also not being used in "toy" pistols either.
You want cheap guns? You like cheap guns? Good for you. My main point is that you have been programmed to accept less for more $$. I went way out of my way to replace Colts plastic trigger in an otherwise nice pistol. Colt saved 2 or 3 bucks!
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