Specifications
According to Wes Grant of M.S.T.N. a premiere small arms builder, these weapons were initially built in-house with the only specifications being the ability to shoot any 5.56 x 45 mm cartridge in inventory (at the time this included the first iterations of the 77-grain (5 g) Mk 262 Mod 0 cartridge), and that the weapon have a barrel 16 inches (406 mm) in length.
The barrel blanks are made by Lilja Precision and then chambered by Compass Lake. They have a 1:8 in (203 mm) twist and are stainless steel. They have a unique heavy barrel profile, starting with 0.980 in (25 mm) in diameter for the first 2.60 in (66 mm) of length, then narrowing down to 0.850 (22 mm) in diameter, 0.750 in (19 mm) in diameter underneath the front sight block, and 0.725 in (18 mm) in diameter to the muzzle. The barrels have the Ops Inc 12th model suppressors with the specified muzzle brake to mount the suppressor. A carbine-length gas system is used. These barrels were mated to flat top upper receivers, and back up iron sights (BUIS) from KAC (knight armament corp).
Beyond this, exact specifications vary. Since they were built in house, they seem to have been accessorized to personal preferences, with fixed (A1 and A2 styles) and retractable butt-stocks. (Original 4-point and improved 6-point Colt stocks, and the Crane/SOCOM/LMT stock are all in use.) Recon rifles built by Crane are reportedly all fitted with a free-float handguard system, the most popular being the Knight's Armament Co. M4 Match RAS and the LaRue free-float handguards in the longer lengths (which protect the barrel and provide more area to mount tactical accessories). Some operators reportedly use various back-up iron sights (BUISs) by Knight's, ARMS Inc, and Troy Industries, while others do not. The range of optics used on Recon rifles is wide, with various models by Trijicon (like ACOG TA01, TA31F), Leupold (TS-30A1, TS-30A2), and NightForce in use.
Due to the secretive nature of the end-users, first-hand information and data regarding the Recon rifles seems to be quite rare. How much these specifications have changed with regards to Crane's "production" weapons is unknown.
Read more about this topic: SEAL Recon Rifle