The U.S. Army is introducing a new shoulder-fired weapon that has the potential to change infantry tactics and revolutionize infantry warfare in a way unseen since the Battle of Königgrätz in July 1866. That battle, which marked the beginning of the end of the line infantry attack, saw Austrian troops carrying muzzle-loaders outgunned by Prussian infantrymen carrying breech-loading needle guns.
It's big and heavy, though apparently effective. They puff it nicely: "No longer will our Soldiers have to expose themselves by firing and maneuvering to eliminate an enemy behind cover. Our Soldiers can remain covered/protected and use their XM25 to neutralize an enemy in his covered position."
Maybe so, if you have enough of them. But I assume that the other side will have some too. Then what happens to your protection? Maybe it does mean new tactics, but it won't be quite as pretty as they make out.