Sentence:  The American firearms and ammunition manufacturers through diligent research and technical development have replaced the muzzle loader and slow firing single shot arms with modern fast firing autoloaders , extremely accurate bolt , lever , and <WSD>slide</WSD> action firearms . 
Meaning of the word marked with <WSD> tags:  action mechanism in a modern rifle or shotgun; a back and forward motion of a sliding lever ejects the empty shell case and cocks the firearm and loads a new round