Buy a chronograph & find out what sort of performance your getting with factory stuff. Then work up loads that perform similarly. In most instances the best you can do is duplicate the performance characteristics. It's not like Winchester or Federal is going to give you their recipe. Besides, it seems to me that exceeding factory ammo performance is one of the goals of reloading. It's been my observation that since factory ammo is essentially built to work OK for most people, most of the time, it's not really much of a trick to make your home grown stuff shoot better.