$300k on issues that go $20; $30; $50 lends you quantities of 15k; 9.7k, and 6k -- this is for issues that trade daily in the millions. Turn on your platform, cue up both contracts/minute and trades/minute. Know the difference between the two. Bring up 1min charts that have Volume included. Bring up a DOM that includes cumBid and cumAsk. Then watch for a while. The answer to "Can I trade X amount without affecting price?" depends entirely on how quickly you wish to be out of the trade, versus how much is traded during that (trader-defined) time period. Let us know what you come up with.