Associated Gun Clubs (AGC) rules are posted here.
http://www.associatedgunclubs.org/rangerules.htm
Basically, Firing at bottles, cans, metal targets, rocks, or any rounded target which may deflect a bullet at any angle, is prohibited on all ranges. I have seen people fire at objects such as ballons or clay targets, but paper is the target most shoot at.
I recommend joining the Garrison Rifle and Revolver club. They are one of the largest gun clubs in the AGC. To join it's $200 for the first year and $170 thereafter, which is basically the going rate for all the gun clubs. The memberships run January to January, but if you join now I believe the price is half, $100. Call or e-mail Brian Beverly (
http://www.associatedgunclubs.org/mc-garrison.htm), or just show up at the monthly meeting, which is the second Tuesday at 8 pm each month in the building at the trap range.
It's only about a 10 or 15 minute drive from where you're at. Directions are:
The range facilities of the Associated Gun Clubs of Baltimore, Inc. (AGC) are located on Marriottsville Road in northwest Baltimore County, at the intersection of Marriottsville Road and Wards Chapel Road. The AGC ranges are approx. 3½ miles west of Liberty Road (Route 26), approx. 5½ miles north of Interstate 70, and about 1 mile east of Patapsco State Park's "McKeldin Area". The gravel road entrance leading to the 200 yard (high power) range, the Bow range, the upper range house (Memorial Hall) and the trap range is located on Marriottsville Road just west of Wards Chapel Road.. The gravel road and parking lot entrance leading to the lower range house, the 100 yard Barnes range, and the 50 yard pistol range, is located on Wards Chapel Road just north of its intersection with Marriottsville Road.
Here's a map.
http://www.associatedgunclubs.org/map.htm