Mr. Dante used an assault rifle for the first time at the range; he switched the fire selector to the single-shot mode. He started off with an integrated muzzle brake trench warfare-style assault rifle, where the muzzle brake diverts high-pressure gases to either side of the barrel, providing the shooter with ample horizontal stability. As for muzzle rise, that called for a strong chap to manage it with a grip.
The reason it was known as trench warfare-style was that such a gun was used in trenches, where there was no need to conceal oneself. The good rate of fire coupled with the 7x54mm caliber bullets provided ample lethality—the reason for the use of the long 7x54mm cartridge was to ensure sufficient penetrating power to pierce through all sorts of Chaos armor.