SIG50 .50 BMG Rifle – First Photo! Posted December 23, 2010 in Rifles by Steve Johnson with 32 CommentsTags: .50, .50 BMG, 2011, rifle, rifles, sig50 The Firearm Blog is first on the ‘net with a photo of Sig Sauer upcoming SIG50 rifle. The Stock. Adjustable cheek and spacers to adjust length of pull Four baffle muzzlebrake It has a 5 round magazine, full length rail, bipod, adjustable stock, fluted 29″ barrel. The MRSP is $8,999. Win the new Springfield Armory XD-9 Mod.2 TFB's first ever gun giveaway.