Food for the Swiss Babies

[dr.jayakumar]

sad me... can't fit in there.

[xl_target]

MOA, That K31 is in beautiful shape. Is that the original stock?

[MoA]

XL: The gun is 100% orginal. Have kept it in the condition I recieved it. Nothing has been changed or retouched.

Forgot to take the camera to the range yesterday, so no pics.

The K31 stays in the 9-10 Ring quite easily. While with the STGW curbing the urge to blast away keeps you in the same performance window as well.

Ofcourse once you begin to blast away accuracy goes out of the window. But it is a lot of fun.

[Hannibal]

I recently got a Swiss brunette, and love the strait pull as I'm left handed and left eye dominant. The ammo is expensive, most people where I live end up reloading,

Check out swissrifles.com if you have not already.

[xl_target]

Havent started hand loading for the K-31 yet, and you cant for the STGW due to the fluted chamber.

I can't get over the great shape that rifle is in.

MOA, how badly does the fluted chamber of the Stgw score the brass? Are they beyond saving once ejected?
If you get a chance, could you post a photo of the brass?
Thanks

[MoA]

This is a pic off the web. The fluting in the chamber is both longitudnal and lateral. So the cases get chewed up pretty bad. Further GP11 ammo is berdan primed which makes reloading quite a pain. I dont bother reloading berdan primed cases.

The Privi ammo is boxer primed, so can be reloaded. The cases fired from the STGW can be full sized and used for the K31. However I shoot the Privi ammo I have in the K31 and avoid having to full resize. Though in all honesty since I have sufficient GP11 I havent reloaded for the K31 yet.

[Vikram]

Interesting, MoA. Any idea why the STGW's chamber is designed that way? What's the point of having a fluted chamber that mangles the cartridges like this? I am asking because I do not know.Thanks.

Best-
Vikram

[MoA]

The STGW is blow back design. The gases from the cartridge flow back and work the bolt.
More here

[xl_target]

Thanks for that photo, MOA. That explained a lot. I didn't realize that the damage would be in different directions like that. Under the shoulder like that, I don't know if full length resizing will fix that.

Vikram, The H&K G3 and the MP5 also use a fluted chamber. Another advantage of a fluted chamber is that it aids in extraction (prevents cartridges from sticking to the chamber wall).

[TwoRivers]

The STGW is blow back design. The gases from the cartridge flow back and work the bolt.
More here

NOOO! It's roller, or hesitation, locked. The chamber flutes allow some gas to flow back, and "float" the front half of the case, as otherwise there is a tendency to rip the base off. The case is still clinging to the chamber while the bolt is starting to move back. The odd shoulder crushes the case and prevents bolt bounce, to prevent the bolt from slightly bouncing back, and firing out of battery.

A cartridge like the 7.5x55 Swiss would require about a 15-18 pound bolt to work as a blow back.

I believe the Tokarev, a locked bolt design, was the first to use the fluted chamber to ease extraction.

[MoA]

Two rivers, the STGW is very much a retarded blowback. And from what little I knowinspired from the MG42/STGW 44 loosely.
The bolt actually does require quite a bit of work to cycle, given the huge recoil spring may well require force in the 10-15 lbs range.

Another pic off the web of a sectioned STGW chamber.

The Shoulder of the case is not crushed in anyway. The deformation is from the fluting.

[TwoRivers]

First of all, the MG42 and StGw44 operate/lock on totally different principle. A delayed blow-back has an unlocked bolt at the instant of firing, but then slows down movement of the bolt by having it overcome mechanical disadvantage.
A roller-locked mechanism, on the other hand, is solidly locked at the moment of discharge, but at the shot impulse rapidly unlocks. That confuses some English-speaking writers who lack the technical background to figure out how it works. So they call it a delayed blow-back. But it is not. If you left the locking rollers out of the bolt, it would become a blow-back. Delayed only by the back of the receiver; and than your facial bones. So don't do it.
The circular "groove" at the shoulder, essentially a double shoulder, or ridge, crushes the shoulder upon chambering of the cartridge, and kills bolt bounce.

[timmy]

Actually, the STGW bolt is not locked in the same sense that a roller-locked system, like a CZ 52 pistol, uses. In the roller locked system, the barrel moves with the slide like the short recoil action, except that it doesn't tip -- it only moves in one plane, not two. The barrel is locked to the slide long enough for the bullet to exit the barrel and the pressure to dissipate after the bullet.

In the roller-delayed blowback, like the STGW, the barrel does not move. Also, the bolt is not truly locked. Rather, it uses roller cams working in recesses in the receiver and forcing the bolt carrier back at a large mechanical disadvantage to delay the opening of the bolt. Check out this diagram:



Here, you see that the blue roller cams are forced against the inclined ramps in the receiver recesses by the green bolt head, upon which chamber pressure is acting. The cams, forced together by the shape of the ramps in the receiver, press against the sloped sides of the red bolt carrier sloped faces. So, the pressure in the chamber is counteracted by the severely disadvantageous leverage that the bolt head must overcome to push the bolt/bolt carrier/roller cam assembly rearwards against the recoil spring.

Removing the cams would allow the bolt head to act directly against the bolt carrier and recoil spring with no mechanical disadvantage -- a straight blowback operation.

This Wiki illustrated writeup shows how, by contrast, the roller locked breech works in the CZ 52 pistol, where the slide (or, in other uses, the bolt) is actually locked to the barrel, which recoils with it until the action is unlocked by allowing the rollers to exit from the locking recesses:

http://en.wikipedia.org/wiki/Roller_locked

[MoA]

TwoRivers: The MG42 and STGW44 did have an influence on the overall design of the 57. Whether or not you agree is a moot point. The literature on the STGW 57 describes it as a delayed blowback. Rudolf Amsler admited to being influenced by these designs.
The cartirdge does float on the gas cylinder formed by the fluting to aid extraction, and yes the bolt is locked at the point of firing. However from what I know this is quite different to other roller locked mechanisms.

In any case we can sit and argue about designs, but I think I am going to the range to shoot it instead.

[drifter]

I wish I have the chance to join the party in UK I am sure it is going to be a blast .

reg,
drifter.