If you haven't bought it yet, let me pass along this bit of info. If you ever need a cylinder for this model, they are not as readily available for (what I believe) is a reasonable price. If you are buying a used saw that doesn't have the compression fully disclosed, there is a risk you will be looking for parts that may just wish you put the extra bucks into a new saw... 372xp for instance or a comparable Stihl. Used cylinders are hard to come by as well. I've been looking for a few months. In fact, there's a new one on ebay now, for over $170 and it hasn't ended yet. And Randy has one with the piston for 270 or so... hasn't sold one since I've been watching. And its about the same to get one rechromed.
My advice is put the 300 towards a newer one. woojr