The most common question a coach gets is what type of ammunition should I buy. Well, we can narrow it down fairly quickly by using what we know.
The two most common shotgun gauges (sizes if you will) are 12 gauge and 20 gauge. You must use the correct ammunition gauge that matches the gauge of your shotgun. 20 gauge is easy to spot here in the United States. All shells are yellow. Now that we know what gauge we need next is shell length.
Modern shotguns will accept 2 3/4 inch shells. Check your owner's manual, or the side of the barrel closes to the trigger. No shells longer than 2 3/4 inches are allowed.
Shell weight is noted on the box in ounces. For 20 gauge, nothing larger than 7/8oz for skeet. To keep it simple, get 7/8oz in 20 gauge. For 12 gauge, nothing over 1oz. First, anything greater than 1oz does nothing for you.
Velocity contributes to noise and recoil at the simplest level. Keep velocity around or under or around 1210 is perfect. Not uncommon to see 12 gauge around 1145 feet per second. There is also ammunition that runs 1350 feet per second. Just not needed for the beginner.
This is a number that equates to the size of the shot in the shell. Number 8 shot is by far the most common, with 7.5 coming a close second. Nine shot is less common in big box stores, but very common for skeet shooting. The larger the number, the smaller the shot size. For beginners, the number 8 shot will be sufficient.