Edit: *Yeah I know (now!) the question was for 2013 but the basics are similar enough*
Most full power rifle ammunition in military use will go through drywall, wood sidings and such like with ease and while some mid power rounds might not fully penetrate things such as cinder block, most can happily chew through if you hit the same general spot a few times (including even pistol ammo).
I don't recall what the specifics are in 1st Ed. but in 2nd Ed. if the target is partially obscured it's automatically one level of difficulty harder to hit. However, the Referee should also consider that if you see a head in a window, you pretty much know where their body is in relation to their head and so the shot probably shouldn't be penalized.
If the hit does succeed, then you have to determine what part of the body was hit and then if the round actually penetrated the cover.
This is the example given in the 2.2 rules - "For example, a character is under cover behind a tree. The referee decides that, since the character is firing a weapon, his or her head and right arm are exposed. If the PC is hit in the chest, the shot strikes the tree instead and provides an armor value of 12."
There are charts in the rules to determine the hit location of the target and the Armor Value of any cover they are behind plus how to determine if the round penetrated the cover and how much damage potential it has left, but I can't recall them offhand - unfortunately the PDF I have from Far Future has the page numbers cropped
Now if you're after some real world info to give you a feel for what can happen in regards to penetration, I can't rate this site, "The Box 'O Truth", highly enough. There's plenty of pages to go through but the guy who runs the site does nothing more than take various objects and shoots them with various types of ammo and photographs the results - these include wall material, wood boards, car bodies, padlocks, bulletproof glass and even sand. They also try to recover the projectiles to see what happened to them as they hit the test material.
http://www.theboxotruth.com/docs/theboxotruth.htm
These guys on YouTube do similar stuff except they video it, this episode deals specifically with cinderblocks.
http://www.youtube.com/watch?v=mYFrskJKye8