First you need to google what you have asked here and look under google images to look at those type so bullet holes in that type of galss. Now you will need to used or get some Sheets of clear styrene or use clear plastic packaging. Now there are lots of ways to make this effects: From using paint thinner to drawing the cracks on the clear plastic. Now It's a process that may not start out the way you think but the end results will be what your looking for. Now I'm going to take some time and ptry and pull up some of my old photos of projects.
So what I will do is start some work on one of my next WWII and modern windows to try and show my own way of doing it. Now I must, must caution you this will be my own way of doing this. An I'm not the a supper Pro at this but I will do this for you M8. Give me a little time to do the work and then come back after uploading all my work photos. Ka??
Oh and remember the closer a round is shot at plane glass the more you will have a full blow out. Now on modern glass and safety glass you don't see as much blow-outs as you can in WWII windows. Now Bullet holes shot in glass from ferther away (WWII type) will give you that small hole with that webed look. Now if the round is of a large caliber round and you would have to thing is this shot clost or far away. This will let you or start you thinking how big the smallor larg the holes should be in the window or winsheld.
Any way let me get to work on this new project.