Why would a slightly better infantry rifle for only one of the major powers shorten the war by a few months? It'd have butterflies from individual soldiers being saved by their faster rate of fire, but it wouldn't effect the war on a large scale.Basic results, higher Axis infantry casualties,not much effects in Asia right away, but serious effects in the European theatre of operations,shorting the war in Europe by a few months.
The shift of forces into Asia a few months earlier would have serious effects on post war Asia.