Pipes, Plumbers, and Other Spare Parts Construction of truly improvised firearms relies mostly on the available cartridge. The ubiquitous .22 cartridge is the favored caliber. Its availability is doubtless the major reason, but there are other factors worth considering. This homemade firearm is being produced and sold along theMexican/U.S. border for less than $35. It measures 5 1/4' x I 1/2" and neighs just 9 ounces. It fires two 22 Ut cartridges, has rifled barrels, extractors, plus a firing and cocking *vice for one or both barrels. The sample submitted to the FBI vras rated as excellent in vrorkmanship. (Courtesy of Chula ”*10. California, Police