Sentence:  The American firearms and ammunition manufacturers through diligent research and technical development have <WSD>replaced</WSD> the muzzle loader and slow firing single shot arms with modern fast firing autoloaders , extremely accurate bolt , lever , and slide action firearms . 
Meaning of the word marked with <WSD> tags:  substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)