My guess is that you are using a chain with a bigger gauge than your bar is made for (something like a .058 chain in a .050 bar).

There are 3 measurements you need to order a chain:

1) Pitch - Length of the drive links
2) Gauge - Thickness of the drive link
3) Links - How many links you need to fit a particular bar

On your bar it shoud state what chain it is designed for. It should say how many links, what pitch and what gauge chain you will need.

You must match the pitch because your bar probably has a sprocket in the nose. If your chain pitch does not match the bars pitch, it will be like having gears that do not match. For that matter there is a sprocket on saw that also must have the same pitch as the bar and the chain.

You should match the gauge. You can run a narrower gauge chain in a wider gauge bar but it is not the best thing to do. It will let the chain rock side to side and could contribute to uneven bar wear, curved cuts and binding. There are basically 4 gauges on saws (.043, .050, .058, .063). There are some other larger gauges on harvesters but you will likely never see them. Smaller saws will run the .043. Stihl uses alot of .050, Husky uses alot of .058 and bigger saws can use .063. Gauge is not worth fretting over. Get the gauge your bar needs and a gauge that you can easily get locally.

Links are a matter of length of your bar. Any decent shop and most poor shops will be able to make you a chain of however many links you need if they do not have what you want in stock.

If you are cutting in clean wood with no debris, get a full chisel cutter. It has a very sharp point on the cutter and is very aggressive. It does dull quickly if you hit something or there is alot of grit in your cutting. Semi chisel is not as fast but it is more durable. Either will cut fine, but putting freshly sharpened full chisel chain into poplar is like butter.

Oregon Chain FAQ