Rails frame internal, and slide external

[brutus51]

Sig came up with the idea first in the much touted P210 which is often billed as the most accurate 9mm. Never shot one so I can't say if it's true but my CZ 85Combat is by far and away the most accurate 9 I have ever owned and I've owned quite a few varieties in my lifetime.
Wondering why Sig abandoned the design?

 

[Jim Watson]

Wondering why Sig abandoned the design?

They haven't. The US made P210A is considerably different from the Switzers but retains the reversed rails.
As to other models, I assume that stamped sheet metal slides were less ameniable to the design and plastic guns aren't being built for target shooting.

 

[tercel89]

All the CZ's I have seem to be great. I will say that these newer Sig Sauer pistols are not great at all. Their quality has went down drastically in the last few years.

 

[CapnMac]

Really, there's not a lot of difference between the two designs.
Allegedly there's more machining (or more material used) in the "inverted" rail design.

Accuracy in auto pistol is more about how repeatable the muzzle and breech position is, rather than rail design and/or fit. Recall that the sights are typically affixed to the slide, so, any slide-to-barrel variances are reflected in how the sights align (mostly, generally, YMMV)

The "square hood" barrel to slide lockup tends to "correct" where the slide lands in the frame as yet another gross generality.

One of the things about self-loading pistols is that, if a thing is really more successful, everyone adopts it. The Browning tipping barrel locking system being a good example of this. If the inverted rails were enough better to matter, everyone would offer them.

 

[tarosean]

Accuracy in auto pistol is more about how repeatable the muzzle and breech position is, rather than rail design and/or fit.

This....

 

[shoobe01]

Sig came up with the idea first in the much touted P210 which...

Charles Petter — Swiss by birth, and an officer of the French Foreign Legion in World War I — designed the inverted slide rail pattern, the closed cam path locking (seen on CZ, Sig 210, "modern" Stars, etc), removed the separate barrel bushing (see: everything but old school 1911s), and created the modular trigger groups (also on 210, similar on the same Stars...), and more. Very cool stuff. Worth looking into the history a bit but... it's not much talked about.

His ideas all gelled into the the French Modèle 1935 SACM pistol, adoped for service and something like 80,000 made:

It doesn't just look a lot like a smaller (it is smaller, in 7.65 Longue which is... very small) 210 but is the parent of it. This is a direct and documented link. In 1937 SIG purchased a license from SACM to up-scale it to a more reasonable caliber, and designed their model 47/8 handgun, which became the P210.


Note the Russians-invented-everything crowd insist Tokarov invented the modular fire control group, but while it pre-dates the Petter design, it also wasn't released until he'd started his work (so parallel design) and is only part of the lockwork so not the same thing.

 

[5-SHOTS]

I have a Pardini GT9-1 which has internal frame rails. It's a super accurate pistol but, as CapnMac already said, it's probably because of other factors rather than the internal rails, factors like barrel-to-slide fit (at the muzzle, ejection port, breech), precision of the chamber and rifling, unlock timing, things like that.
Surely the internal frame rails offer a lot of rigidity and stability also because they are practically always full length. But the main feature of pistols with internal frame rails is the fact that with this configuration it is possible to obtain a lower bore axis than external frame rails pistols with hammer. That's one of the main reasons why CZ and Tanfoglio pistols are so popular in race competitions. But in terms of accuracy you can get the same or better results with pistols with external frame rails pistols such as the 1911 family, P226 family and even the Grand Power K100 family.

 

[The Glockodile]

It's really the handfitting and craftsmanship involved, just so happens this make and model of pistol came with a good pedigree.

 

[Drail]

The system of the rails has nothing to do with accuracy.