Why do polymer pistols have metal rails?

ForaFewDollarsMore

ForaFewDollarsMore

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Basically if its so strong why do the Glocks, M&P's, XD's, Ruger SR9 have metal rails for the Slide to ride on?. Isn't the Ruger P85 to P95 without metal rails for the slide. The slide just rides on the polymer frame. I wonder if you look at both the metal and polymer under an electron microscope. What the difference would be. I pretty sure the metal would not look smooth at all.

Anyways interested in some info about this.
 
^ that's my guess. There are different measures of strength so when someone says polymer is strong, they mean maybe tensile strength, ability to withstanding blows, or whatever... but metal grinding back and forth on it might not be what they had in mind.
 
Considering that all the plastic guns I've seen have metal tabs or buttons of some form for the slide to bear on I suspect that you may be wrong in thinking that the Ruger slide runs only on the plastic.

It's not only a wear thing either. There's the friction of different materials rubbing together to consider as well. But mostly it's likely that whole "different sort of strength" issue. The small contact area of the rails would tend to be beaten out of shape from the impact pressure. But that doesn't mean that the frame can't deal with the overall stress just fine.

It's an extreme example but pushing a screwdriver into a block of styrofoam. Easy eh? Now put a tab of plywood onto the foam and push on the plywood. Suddenly the foam is strong enough to hold your whole weight just because it spread out the pressure to a bigger area. And that same function is one of the reasons for having the metal inserts in the plastic frames.
 
Ruger discontinued almost all those models, for a good reason.
The only poly frame ones like you are thinking are the p95 and p97 and now p345.....the rest are alloy frames. Maybe the sr9, but haven't played with one yet.
And they are pure poly, no metal inserts in those models.
 
Hitzy said:
Ruger discontinued almost all those models, for a good reason.
The only poly frame ones like you are thinking are the p95 and p97 and now p345.....the rest are alloy frames. Maybe the sr9, but haven't played with one yet.
And they are pure poly, no metal inserts in those models.
Click to expand...

SR9 has metal inserts. Small ones in the rear and longer ones above the trigger
 
I think it's for durability and friction/high stress issue. Polymer are strong, but not enough to endure thousands of cycling by a metal slide. Even if polymer are strong, they are no guns with polymer slide guess why ??? Too much stress, the same reason why they are putting metal insert on high stress rail.
 
The nylon (polyamide) that most polymer guns are made of (I think Ruger uses polycarbonate) is too 'flabby,' and flexing would bind the slide on the frame.

Nylon on steel is actually self-lubricating.
 
I think also for the polymer to be strong enough for repeated use, I think it'd have to be thicker? If you look at the thickness of the frame, it's thicker than the rails. While the metal rails can be thinner? Just a guess really
 
Nobody claims that polymer is stronger or more durable than steel, just that there are los of gun parts that dont NEED to be metal so you may as well make them polymer. Polymer rails would not last long or preform well when shooting in volume. Just remember if you run 1000 rounds through a Glock as fast as you can the guide rod will melt and the front end of the frame will soften up. I imagine if you had polymer rails the slide might come off and hit you in the face.
 
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