The Seals did have a modified S&W M39 based on the steel frame version of the gun. It had higher sights (higher and uglier than the protective ears on the 4506) so as to look over the suppressor (about 5" long, slightly under 2" in diameter), a modified slide stop which served as a locking mechanism to keep the slide from cycling (hush hush). The latter was held on by a castle nut. Supposedly it was used to kill dogs (hence the nickname, "Hushpuppy"). An experimental version built on the higher capacity (evil evil evil) M59 was also built.
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