If a guy is worried about getting the cheapest gun, he is generally too cheap to feed it the best ammo and will resort to whatever is the cheapest he can find.
Which is why I qualified my comment by stating that it depended on ammo selection. However, a lot of people seem to believe it is simply not possible to use an SKS safely in a surburban area, and that is not true.
Comblock HP ammo from what I've read acts pretty much the same as the FMJ version.
Actually, some versions of the Wolf 123gr SP do very well at reducing penetration; though you have to do your research and make sure you get the correct version.
High dollar frangible ammo is not common and therefore the chances of it being used in a defensive situation from an SKS is about the same as Willard Scott squeezing back into his original Ronald McDonald costime.
You can buy a box of the Hornady TAP online for around $20 and have it delivered to your door in most states. This is not frangible ammo; but Hornady's Vmax bullet.
FMJs drill through what they hit and the next thing and the next thing until enough energy bleeds off to stop unless something substantial is hit and the bullet's path is effectively obstructed.
Any bullet, regardless of caliber or type, continues down range until it bleeds off enough energy to stop. FMJ doesn't start with more energy; but penetrates because it is more likely to stay together and retain its momentum. A slow moving pistol bullet also stays together and retains its momentum, which is why it can sometimes penetrate more than a faster rifle bullet that breaks up due to velocity and/or small size.
Care to stand behind five layers of sheetrock while I rock off a clip of ammo? Let me know how that works out for you...
Sheet rock isn't a substantial barrier. If you are basing your choice of defense in a lethal force situation on what doesn't penetrate sheet rock, you have your priorities ass-backwards. If I was worried about damage to sheet rock, I'd use airsoft.
I'd wager you would not see 1 pellet of birdshot penetrate 3 conventional walls but would be a might unconfortable betting your life on layers of drywall protecting you from one or two 7.62x39 FMJs..
Which is why:
1. I don't use birdshot to defend myself from an immediate threat of death or serious injury if I can avoid it.
2. I don't use 7.62x39 FMJ for self-defense if I can help it.
3. I don't rely on drywall for a safe backstop; but assume any round (pistol, rifle, shotgun) is going to penetrate to the brick exterior at a minimum.
People get wrapped up over overpenetration to the extent they make questionable choices ammo-wise. It seems they also assume every confrontation is going to go down just like at the range - an unobstructed silhouette target presenting an open frontal shot. If you've got someone inside your home that rates lethal force, THAT is your primary problem. It represents a greater threat to the safety of you, your loved ones, and neighbors than overpenetration does. I can always choose not to take a shot with a bad backstop. I can't take a round that won't penetrate drywall and magically make it go through whatever is between me and the bad guy's vitals.