Swiss 7.5x55mm Manipulierpatronen for the STGW 57


#1

Below you see a scan of three Swiss 7.5x55mm drill rounds or Manipulierpatronen for the Sturm Gewehr 57. The small step at the shoulder is to clear the step in the chamber of the STGW 57. The full-length, spitzer pointed one is the Model 1959. The short round-nosed one is the Gewehr ManipulierpatroneTreib 64 or drill grenade gartridge. This one is marked around the head: GW MANIP TREIB-PAT using a roll die.

My question relates to the intermediate length one, I am fairly sure that it was made by converting stocks of the Model


#2

gravelbelly

I think that the 2 dummy rounds (in the centre and the right one are used for the StGw 57 and for the MG 1951/71)

The one at the centre(Manipulier pat 11) was used for the StgW 57,the raison for the rounding of the nose was that the spitzer nose by frequent use of exercises causes severe damage to those dummy rounds.

The Manipulier Pat 11,model 59 at the Right were used by the MG 1951/71

pict’s out of a Schweizer Army manual for the MG 1951/71


#3

gravelbelly

For the ( live grenade cartridge)Treibpatrone is no special charger,not that I have ever seen.
Also at the Swiss army Manuel about the StGw 57 they fill up the special magazine by hand.

pict’s of the magazine

At the left K31 and right the StgW 57 special magazine for schooting the rifle grenade.

pict’s of a couple of Swiss 7,5x55 grenade cartridge boxes


#4

What is the function of the step in the chamber shoulder on the StGw-57 ? Live rounds do not have this feature, but the dummy cartridges do?

Interesting stuff!

AKMS


#5

[quote=“AKMS”]What is the function of the step in the chamber shoulder on the StGw-57 ? Live rounds do not have this feature, but the dummy cartridges do?

Interesting stuff!

AKMS[/quote]

AKMS,

The step provides controlled resistance during the final couple of millimetres of chambering. If a live round is ejected without being fired is has the step formed on its shoulder. The striations of the flutes in the forward part of the chamber will also be visible in this new shoulder step. The STGW being an automatic weapon with a spring plunger ejector in the bolt face can “over ram” a cartridge leaving it out of reach of both striker and extractor. The step in the shoulder provides sufficient resistance to hold the cartridge back firmly against the bolt face. A fired and ejected case has the stepped profile and the evidence of the chamber flutes running back from the mouth to about a third of the way down the body.

As the chamber is stepped and the dummies are solid then they must also be stepped.

gravelbelly


#6

Thank you for the explanation, and I understand what you described, but I still do not understand the need for the step in the chamber. I do not understand how, in a properly headspaced chamber, a cartridge can be “over-rammed” to the point where the cartridge is not held by the extractor. There are many, many rifles and machineguns using a spring plunger ejector that do not suffer from this problem. There must be more to the design of the StGw-57 that causes this to happen. Does it fire on automatic using some variation of advanced primer ignition? Does the fluted chamber have any relation to the “over-ramming” problem?

AKMS


#7

[quote=“AKMS”]Thank you for the explanation, and I understand what you described, but I still do not understand the need for the step in the chamber. I do not understand how, in a properly headspaced chamber, a cartridge can be “over-rammed” to the point where the cartridge is not held by the extractor. There are many, many rifles and machineguns using a spring plunger ejector that do not suffer from this problem. There must be more to the design of the StGw-57 that causes this to happen. Does it fire on automatic using some variation of advanced primer ignition? Does the fluted chamber have any relation to the “over-ramming” problem?

AKMS[/quote]

AKMS,

I agree that other MG’s manage without a stepped chamber but many of these use other means such as a short headspace which is not so obvious. The headspace gauges for some MG’s are a few thou’ shorter than the equivalent bolt actioned rifle. The Belgian MAG has a short chamber, if you pull the trigger on a dummy and then eject it you will find that the shoulder has been set back a little. Put that dummy back into belt links and pull the trigger on it again and 50% at least will not extract because the pressure of the ejector plunger combined with the extractor spring has shortened it further. These dummies are now scrap. This applies to the 35x228mm Oerlikon due to the velocity or ramming and the UK built 20x110mm Hispano guns. I suppose it depends very much on the feed system, if the rim of the cartridge is neatly slid behind the extractor claw before the round is stopped by the chamber shoulder then rounds will not be crushed. There will be more learned men out there who can explain it better, I am mainly going by my own experience (and mistakes).

gravelbelly


#8

Interesting. Here in the US, the general consensus is that MG chambers are on the “loose” side (M-60, M-240 and M-249). As such, reloaders shun brass fired in these weapons as is has already stretched a bit too much due to the relaxed chamber dimensions…

Back in the good old days, we ran quite a few dummy rounds through our M-60 and M-249 machineguns over and over again with no obvious issues.

AKMS


#9

StgW 57 and his rifle-grenade