M24 Sniper (3.5e Equipment)
From D&D Wiki
The M24 sniper rifle is a powerful firearm which works best at long range. With a long barrel, the shot remains stable on course for some time. The sniper rifle typically only holds one shot, but a magazine can be added for an additional 200gp, increasing its shots to 5 before reloading is required. Regardless on when reloading is necessary (a full round action which provokes attacks of opportunity), the sniper rifle can only fire once per round, regardless of your BAB. In addition, you take a -4 penalty to attack to attempting to fire within 30 ft. of the target.
In older-time campaigns the M24 sniper rifle may show up as a bizzare clockwork device powered by alchemetical means, but the result is the same.