The max weight thing is a club rule here is the rule:
Weapons used in competition shall be serviceable and safe. Should a weapon become unserviceable, it can be replaced for use in later stages or strings of fire with an acceptably similar gun of the same caliber and action. No optical sight is allowed on any pistol or shotgun.
Pistols: IDPA rules will be used in regards to handguns.
Shotguns: Shotguns will be semi-auto or pump actions with a barrel length no greater than 22 inches. The shotgun magazine tube may not extend past the end of the barrel more than 1 inch. The shotgun may weigh no more than 1 pound over stock weight in police or "riot" configuration. Any device on the weapon to carry extra ammo must comply with length and must be secure enough to hold the ammo during rigorous movement.
Carbines: Carbines will be equipped with a sling or carry strap. Carbines may weigh no more than 9.0 lb. without scope or 10.5 lb. with scope. Carbines will be weighed empty, without mag, but otherwise complete with sling and any other attached accessories. A bipod may be used providing the rifle makes weight with the bipod attached and the bipod extends no more than 14 inches. Iron Sighted Carbines must be equipped with battle sights (i.e. no Redfield target sights). Enhancement of existing battle sights (i.e. National match sights) is permitted.
Holsters and Gear: Holsters must meet IDPA criteria. A competitor's sidearm will be worn for all courses of fire. Competitors will wear their equipment and magazines/spare ammo in a manner consistent with continuous wear (mag pouches, shell loops, etc.). Bags and boxes containing ammo and gear are not allowed on the line or ready area. Mag pouches for the pistol shall suit the holster being used. Duty holsters require duty mag pouches. Mag pouches used with the concealable holster must be concealable as well and carry the mags reasonably tight against the body. Magazine pouches for the pistol or rifle may leave no more than 50% of the magazine protruding from the magazine carrier. This 50% limit includes all portions of the magazine including any base pads. Both rifle and pistol carriers must protect the magazine feed lips. Skeletonized magazine carriers (i.e. IPSC types which do not cover all sides of the magazine, spring clip types, etc.) are not allowed. Devices to hold a spare magazine to the rifle or to the magazine in use must protect the magazine feed lips and must keep dirt out of the spare magazine or a separate protector must be used.
Ammunition: All contestants are required to shoot full power ammo in this competition. Shotguns must be 12 gauge Buckshot (#4 buck or larger) No Slugs. Carbine ammo will be copper plated FMJ and may not be tracer, steel core or armor piercing.