Out here if you want to go skiing in the winter, and there's snow on the highway, you must have either chains or approved snow tires/4wd. Otherwise you'll get stopped by the CHP and turned back. There are various levels of traction device requirement: R1, R2, R3. R1 means it's ok to have snow rated (M/S) tires on a front wheel or rear wheel drive vehicle. R2 means a two wheel drive vehicle must have chains on the drive wheels. R2 means that a four wheel drive vehicle is OK with just snow tires. R3 means 4wd with chains only. The CHP emphasizes that in the winter in snow country everyone should carry chains, regardless (I guess they are in denial about the inability of most FWD cars to fit chains of any type).
The problem, I suppose, is that one can drive for several hours to get to the mountains and then find it's R2 rated and the snow tires on the drive wheels won't cut it, and of course the fwd design means no chains are available to fit the wheels. Don't know how common R2 conditions are, but I recall in the past getting stopped on HW80 in the Valiant and told that from there on out it was "chains only".
Currently I have all-season Michelin radials on the 300M that are marked "M+S". The car also has traction control to limit wheel spin, and I've read that it does pretty well in snow as is. I've not tried it, and not really all that interested in getting the car all gunked up driving in the snow if I can help it.
I've also driven a mini pickup (rwd only) in the mountains in the winter, and had no problems. I remember seeing 4wd's off in the ditch, whereas I was able to stay on the road by maintaining a steady speed, staying well back from traffic ahead, and going very easy on the brakes. So, like people say, a lot of this is how one drives as well as the type of vehicle/drive system/tires.
I did some googling, though, and found a cable chain that works on cars with limited wheel clearance and which might work on the 300M. Link follow...