Build a chronograph, and calculate the velocity & trajectory of a bullet - I recommend 22 short or CCI Quiet since they'll be slow enough to actually measure drop over short distances. Need a *straight* 3/16" dowel, some level bubbles, some hot glue, target stand, large cardboard backing (tall and wide), gun, ammo, place to shoot, calculator, micrometer, long measuring tape, lab notebook, etc.
Make a bore level by hot gluing one of the bubble levels to the one end of the dowel. Clamp gun in padded vise, put your bore level down the bore and get it level (duh). Put the target so the cardboard backing is as close to exactly 5 meters from the face of the muzzle. (metric makes the math easier). Use your laser, a piece of string (checking with one of the other level bubbles), etc. mark the spot the bullet would hit if it went in a perfect straight line. You can be off a little left to right if needed. A few inches above your mark, draw a level line across the target backing. Call the range hot, fire one shot, call the range cold, and go make another level line across the backing a few inches below the hole. Shift the target backing a few inches in either direction, re-check all alignment, go range hot, fire another shot. Repeat this until you have a good selection of holes to measure (statistical sample). You should now have a lot of parallel to gravity lines, with a mark near the top one and a hole near the bottom one.
Next move the target to 10 meters (remember, we're trying to figure out how fast it slows down), and repeat. Then 15 meters, and then 20 and 25.
You now have the amount of movement the bullet made (down), at several known distances. You know how fast it moved in a downward direction (9.8m/s^2). Which tells you the rate of travel over those distances. The rest - muzzle velocity (and then mean & standard deviation to make pretty graphs with), sectional density and ballistic coefficient should be published, and all of that and some math will allow you to determine the trajectory
I did this when I skipped 17 days of physics class in high school... told him I was either fishing or skeet shooting depending on the day of the week... since we covered gravity during that time in the class, I had to show him what I knew about gravity. Got an A for the term
