Steyr’s New STM556

By: Sal Palma

It appears Steyr Mannlicher has made a conscious course change; abandoning the bullpup track with its new STM556 carbine. I can’t say that I blame them given the irrational phobia surrounding bullpup architectures, like the very fine Israeli Tavor and Steyr’s own AUG. I have to believe that military customers have never taken the time to thoroughly evaluate either one.

The reality is that bullpup carbines like the Tavor and AUG address the needs of modern soldiers quite effectively.

For those unfamiliar with the meaningful benefits of a bullpup, I’ll summarize by saying the weapon’s center of mass is further to the rear, in a bullpup, so it is much closer to the operator’s body; making the muzzle more agile and more easily controlled. Barrel length is preserved in a bullpup, which conserves muzzle velocity. In smaller calibers, like the 5.56 x 45, muzzle velocity and bullet geometry are critically important to lethality. Lastly, the bullpup keeps overall length to a minimum; making the design more suitable for close quarters and urban operations.

However, Steyr’s new  STM556  is not a complete departure from its AUG. The gas system and interchangeable barrel assemblies are nearly identical to the AUG. Steyr has incorporated M4-like operator controls, M4-like magazines and large amounts of rail space with a monolithic upper receiver / rail system. The STM556’s upper receiver should be right-at-home mated to any M4 / M16 receiver.


The STM556 is still in prototype form but rumor has it that in addition to the quick change barrel the rifle will also offer quick change caliber.


Steyr has developed a well earned reputation for producing accurate rifles and I’d be willing to bet the STM556 is a solid 1MOA platform.

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