Abstract: A method of manufacturing a preform, the method including positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end, forming a preform from the preform precursor, and thermally treating at least one of the preform precursor and the preform. The thermally treating including sealing the first open end and the second open end of the glass tube to form a closed tube and heating and/or cooling the glass tube to manipulate gas pressure within the closed glass tube.

Abstract: A training/safety plug for use in firearms is provided. In one implementation, the plug comprises a chamber end and a shaft extending away from the chamber end. The chamber end is adapted to fit within a chamber of a designated firearm, the chamber end has a cross-sectional dimension sufficient to prevent the chamber end from extending into a barrel of the designated firearm and further comprises a strike surface for receiving an impact of a firing pin of the designated firearm and a proximal end dimension such that the chamber end is not engaged by an ejector mechanism of the firearm. The shaft comprises a barrel end coupled to and extending distally from the generally cylindrical chamber end; the barrel end of the generally cylindrical shaft further adapted to extend from the chamber end into the barrel of the designated firearm.

Abstract: A training/safety plug for use in firearms is provided. In one implementation, the plug comprises a chamber end and a shaft extending away from the chamber end. The chamber end is adapted to fit within a chamber of a designated firearm, the chamber end has a cross-sectional dimension sufficient to prevent the chamber end from extending into a barrel of the designated firearm and further comprises a strike surface for receiving an impact of a firing pin of the designated firearm and a proximal end dimension such that the chamber end is not engaged by an ejector mechanism of the firearm. The shaft comprises a barrel end coupled to and extending distally from the generally cylindrical chamber end; the barrel end of the generally cylindrical shaft further adapted to extend from the chamber end into the barrel of the designated firearm.

Abstract: A training/safety plug for use in firearms is provided. In one implementation, the plug comprises a chamber end and a shaft extending away from the chamber end. The chamber end is adapted to fit within a chamber of a designated firearm, the chamber end has a cross-sectional dimension sufficient to prevent the chamber end from extending into a barrel of the designated firearm and further comprises a strike surface for receiving an impact of a firing pin and a proximal end dimension such that the chamber end is not engaged by an ejector mechanism of the firearm. The shaft comprises a barrel end coupled to and extending distally from the generally cylindrical chamber end. The training/safety plug renders the designated firearm inert. Methods of training a student to target a firearm or other targeting device are also disclosed.

Abstract: A training/safety plug for use in firearms is provided. In one implementation, the plug comprises a chamber end and a shaft extending away from the chamber end. The chamber end is adapted to fit within a chamber of a designated firearm, the chamber end has a cross-sectional dimension sufficient to prevent the chamber end from extending into a barrel of the designated firearm and further comprises a strike surface for receiving an impact of a firing pin and a proximal end dimension such that the chamber end is not engaged by an ejector mechanism of the firearm. The shaft comprises a barrel end coupled to and extending distally from the generally cylindrical chamber end. The training/safety plug renders the designated firearm inert. Methods of training a student to target a firearm or other targeting device are also disclosed.