A paper by Dr. Engineer Günther Voss

Doctor Engineer Günther Voss came to Spain from Germany after WWII. He worked for the Spanish government but was also a civilian engineer.

While working at CETME on assault rifles he invented some notable bullets. Some of them he patented, like the aluminum cored one for the then developing 7,92 x 40 CETME rifle, or the ones for the 4,6 x 36 caliber with peculiar tip shapes.

In september 1960 he wrote an article in the official Spanish army journal, Ejército. Two years before Spain had adopted the 7,62 x 51 caliber with a special light bullet and load for assault rifle use, but it seems that the army had set its eyes in the more powerful NATO cartridge adopted in Europe and the US mainly.

The article was titled “The unification of the infantry ammunition” and presented the following theories:

  • The NATO round is too powerful and generates a strong recoil. Its dispersion when fired in bursts is twice than that of the Cetme light cartridge (1), offering acceptable impact probabilities at relatively short distances only. Thus the assault rifle in NATO caliber cannot be a substitute for the light machine gun.

  • The NATO cartridge has many drawbacks when used in a machine gun, because of the reduced bullet weight and inadecuate bullet shape (2). Because of this the NATO ballistics are sensibly worse than that of the 7,92 round with sS bullet. This inferiority shows specially at ranges longer than 600 meters, precisely the range at which assault rifles are no longer useful. Thus the machine gun in 7,62 Nato caliber cannot be a substitute for the 7,92 mm machine gun.

According to Dr. Voss, the adoption of a new ammunition for the Spanish infantry should be made adopting the Nato cartridge as a basis, but with the advantages of the short assault rifle rounds and long machine gun rounds being developed in foreign countries.
The high capacity of the NATO-CETME 7,62 x 51 case allows the use of flake powder manufactured in Spain. The smaller assault rifle rounds, as the Nato one, must be loaded with tubular or spheroidal powder that should be purchased abroad.
Rifles in 7,62 x 51 caliber are able to launch rifle grenades with 30 percent longer range than short-cartridge assault rifles.
Plus, in case of an emergency, the CETME rifle can use the Nato ammunition as is. So the assault rifle problem is already fixed.

The machine guns pose other problems because an improvement of the ballistics must be achieved. This can be done only by augmenting bullet length and weight, so only the case and the propellant charge from the NATO round can be kept. But this is enough for allowing the use of this new improved ammunition along with the NATO cartridge in the same gun without any modification (3).
The existing Alfa machine guns need only a change of barrel and a lengthening of the feeding opening by some 2 mm.

In short, Dr. Voss proposed the following:

  • Adoption of the 7,62 x 51 NATO caliber for infantry use.

  • To keep the regulation 7,62 x 51 CETME light round (CSP-003) for assault rifle use.

  • To adopt the 7,62 x 51 CETME heavy round (CSP-004) for machine gun use.

  • In case of need, both the assault rifle and the machine gun can use the NATO cartridge without modifications to the guns or the ammo.

Although Voss speaks of trials with the then regulation Alfa-55 machine gun converted to the 7,62 x 51 caliber, it seems that a new design was also considered. A box of 7,62 x 51 cartridges with the CSP-004 bullet mentions “for MAUSER-CETME machine gun”.


(1) The light CETME cartridge mentioned had the CSP-003 bullet, and the heavy one, the CSP-004. CSP stands for Cobre-Sintético-Plomo (Copper-Synthetic-Lead), and the number after the hyphen is the correlative number. The jacket was not copper but actually gilding metal (90/10 brass), and the synthetic plastic nose filler was black phenolic resin.

(2) Maybe he was referring to the flat-based T65E3 bullet which had been tested at CETME.

(3) The gun would be an Alfa machine gun adapted to the longer CSP-004 cartridge. Voss writes that Alfa machine guns modified for the new heavy cartridge (CSP-004) have been tested to reliably feed and fire standard 7,62 NATO rounds using original belts. Voss does not mention barrel twist rates, but the longer CSP-004 bullet should need a faster rifling than the NATO bullet. However, barrels with this faster rifling could use NATO bullets without problems.



Here’s a drawing of the three 7,62 x 51 cartridges (from Voss’ paper), and a photo of the same.


A graph showing the remaining energy of the cartridges discussed in the paper. From top to bottom: 7,62 CSP-004, 7,92 sS, 7,62 NATO, 7,62 CSP-003.


Top of a box for 50 7,62 x 51 CSP-004 cartridges.

The Alfa-55 machine gun in 7,92 x 57 caliber.

Great Stuff! Schneider
Keep it UP!

Nice article and interesting information…a German and Spanish Adaptation of a Nato case design into an originally Italian (Breda 37) gun converted to belt feed design by Spain (Alfa-Oviedo).

Doc AV
AV Ballistics.