be a stock, unmodified and readily available factory gun with a maximum barrel length of . As a rule of thumb, bolt action pistols are not permitted in NRA Conventional, which excludes bolt action pistols and therefore makes revolver and break action pistols competitive. Bolt action pistols are however permitted in IHMSA Production, except in IHMSA Production Revolver which is restricted to revolers. Other differences between the classes are listed in the table below: NRA Unlimited and IHMSA Unlimited classes The NRA Unlimited and IHMSA Unlimited classes permit any gun type (including bolt guns) with a maximum barrel length of . Differences between the classes are listed in the table below: Rifle divisions Metallic silhouette rifles most often have scope sights. International divisions IMSSU Silhouette Rifle Also called High power silhouette rifle. A rifle, caliber 6 mm or larger, provided no belted cartridges or magnums are allowed. The maximum permitted weight is , including sights. Any sights may be used, whether telescopic or metallic. Scopes may not be more than above the rifle as measured from the top of the receiver to the underside of the scope tube, nor may the scope be offset from the top center line of the receiver (i.e. no canted sights). Any sighting device programmed to activate the firing mechanisms is prohibited. The stock must be traditionally styled and may not be bent or twisted so as to deviate from conventional configurations such as factory rifle stocks or silhouette stocks as manufactured by Fajen, McMillan, H-S Precision, and others. The barrel may be no longer than . Exceptions to this in U.S. competitions include U.S. rifles in caliber .30 such as the M1, M14, and M1A. These rifles only may exceed the weight limit, and telescopic sights are not permitted on these rifles. The magazine of the M1A or M14 may not be used as a palm rest. IMSSU Hunting Rifle Also called High power hunting silhouette rifle. A hunting style rifle having a maximum weight of , including sights and if applicable, an empty magazine or clip. The intent is to describe a common hunting rifle. Caliber 6 mm or larger, provided that no belted cartridges or magnums are allowed. Sights can be any telescopic or metallic sight. Scopes may not be more than above the rifle. Exception: for rifles that eject the empty cartridge case straight up and that normally use an offset