Complex sentence: Not all AKMs had slant muzzle brakes some were also fitted with the older muzzle nut which came from the older AK-47, most AKMs with muzzle nuts were older production weapons.
Split into simpler sentences: Not all AKMs had slant muzzle brakes; some were also fitted with the older muzzle nut which came from the AK-47. Most AKMs with muzzle nuts were older production weapons.