Polymer frames and steel rails?


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nzo012
December 20, 2008, 09:49 AM
I have been looking at several .45 and .40's for evaluation. I have Sig, HK, Glock and the S&W M&P. All have Polymer lowers except the Sigs. I was looking at the M&P with a machinist and when I stripped it down, he commented on the tiny little metal rails that the slide slides on; saying that he didn't think that would hold up well because that should be the point of the most wear on the entire gun and they were so small. This machinist doesn't machine gun frames, but he does make a lot of moving parts for other machines, so he probably would know something about wear.

Gee, I never thought of that, I never really paid that much attention to the configuration of the rails. So, I broke down the HK45 and the rails were the same type of short small rails; Glock was also similar. The Sig with both the metal upper and lower had slide rails running most of the length of the entire frame. Where the S&W and HK was about 1/2 inch long.

The M&P had some slide rattle when you shook the gun, but the HK didn't.

So, if you have any of these guns break them down and check them out. I'm curious what everyone thinks and what the condition of wear is on some of the guns that have a lot of rounds through them. Has anyone heard anything concerning these rails. I do admit they look kind of weak. If anyone knows the engineering logic behind the rail design, I'd love to hear it.

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J.R.W.
December 20, 2008, 09:53 AM
A good lubricant is your friend. I like the Mil Comm light grease for the rails. Its factory approved by Sig.

The Lone Haranguer
December 20, 2008, 09:57 AM
I have both a Glock and M&P, the Glock for far longer. Neither have any discernible wear on the frame rails.

HKIWB
December 20, 2008, 11:37 AM
I always put a couple drops of lube down the grooves in the slide. I suspect that the finish on the slide will wear off before the metal tabs in the frame wear out or any slop develops in the frame-to-slide area. My HK45 has only 1,700 rounds through it, but the finish is still flawless all along the grooves where the metal frame rails slide. My P30 has 12,000 rounds through it, and its finish is also like new in the grooves.

gtmtnbiker98
December 20, 2008, 03:34 PM
Glock durability has more than demonstrated itself in the 20+ years of service.

THE MACHINIST
December 20, 2008, 04:35 PM
the ruger p-95 series has polymer rails ive had two and they were accurate and showed no discernible wear.

RickW
December 20, 2008, 05:08 PM
I've got a Kahr CW40 with around 1000 rounds through it with no visible signs of wear.

XDShooter07
December 20, 2008, 05:28 PM
I'd say the engineering logic is weight savings. But I also think that Glock, XD, and M&P have all shown their reliability so I wouldn't worry about it.

fastbolt
December 20, 2008, 05:30 PM
S&W refers to their slightly rounded and oval shaped frame rail tabs as 'rocker rails', and their shape was carefully determined by the engineers during the R&D and extensive in-house testing.

We were told in the armorer class that the design of the rocker rails allowed for consistent self-centering of the rail tabs within the slide's rails, and that as the frame rail tabs eventually experienced some expected normal wear that the design would allow for them to continue to 'center themselves' and promote enhanced accuracy. Their design was also supposedly intended to promote an extended service life. They've withstood extensive in-house testing during the development and then subsequent T&E by LE agencies. The only "teething problems" of which I've heard since the M&P was released in Jan '06 haven't involved the frame rails. ;)

Also, the frame rail tabs being located in the steel sear housing block assembly and frame locking block allow for the easy replacement of broken rail tabs at the armorer level, replacing just the affected modular block, instead of having to replace the entire frame in the event of a rail breakage as happens in some other designs where the frame rails are units molded into the polymer frames.

Glock has revised and refined their frame rail tab design regarding rail length and machining methods over the years to improve their design. Last I saw the frame rail tabs were still being plated with copper and then a nickel Teflon finish. This can flake off and annoy some owners, but armorers have been told it's just a cosmetic issue and not a problem.

I remember thinking it was an interesting development when I saw that while the Walther 99 frames rails continued to be molded units within their polymer frames in the full-size models, the compact models started using a redesigned locking block which incorporated the front frame rail tabs.

As a factory trained LE armorer for a few different makes, designs and models of handguns used in LE work, I wouldn't have originally bought my M&P 45 if I'd had any concerns over its service life, nor would I have just ordered an M&P 40c.

As far as polymer-framed pistols are concerned, that will give me a pair of Glocks, a pair of SW99's and a pair of M&P pistols. I have confidence in all of them for off-duty/service usage.

I do, think, however, that the M&P platform offers some design changes and refinements that are very interesting. Very.

The HK USP is also an excellent service-type pistol. I've handled and used a number of them over the years for occasional training and some T&E. I've just never felt interested in them enough to spend my own money on one. Just my druthers. Good pistols, though.

Just my thoughts.

Gun Slinger
December 20, 2008, 08:08 PM
Since there several instances of Glocks demonstrating lifetime round counts into the hundreds of thousands, I suspect that those who designed it knew what they were doing and as such is not something that I would being worrying about. I'd willing to bet that the HKs will also do just as well.

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