I hope that i´ve understand your question correct ^^
If the WS is only one point higher than the Defense Rating (DR) of a Hit Location this means that you made 1 wound (so you cross of 1 Wound Box for this location). For Example a WS5 Weapon hits a Location with DR4, than only one woundbox is crossed off.
Doubledamage is made when the WS is two times higher than the DR. For example a WS8 Weapon would cause Doubledamage on a Hit Location with a DR of 4

(Tripple Damage if the WS is 3 times higher than the DR. WS9 and a DR of 3 for example).
If the WS isn´t at least two times higher than the DR, no doubledamage is done. therefore Weapons with WS 5-7 wouldn´t cause doubledamage on a DR of 4 although they are higher than the DR.
The armor save only applys when WS is less than DR. So with a WS of 3 on a Location with DR 4 or more the model can made an armor save to avoid damage. (With this example on an armor roll of 9+ on a d10)
If the armorsave is passed, no damage is done, if the save misses, one wound box is crossed off.
Hope this is the answer you were looking for?
Well don´t know if there are rules for assault rifles in "Dragon Bones". This supplement is still missing in my collection. In Amazing Warstorys there is none but the soldiers use the standard Sub Machine Gun

But try this one. I made my own stats for a MAR (Military Assault Rifle). Havn´t try it yet but i think it will work ^^
Assault Rifle (3)
Range TH WS
Close Combat - - -
Short 8" +2/x3 6
middle 14" +1/x2 5
long - - -
it´s more a short ranged assault rifle but it should cost 3 Attribute points and therefore it couldn´t have the same range and more shots than the sub machine gun at the same time....