▁Model ▁ 3 4 ▁continued ▁to ▁be ▁manufact ured ▁until ▁ 1 9 9 1 , ▁but ▁Model ▁ 4 3 ▁and ▁ 5 1 ▁production ▁stopped ▁in ▁ 1 9 7 4 . ▁ ▁The ▁model ▁ 6 3 ▁st ain less ▁was ▁replaced ▁by ▁the ▁significantly ▁l ighter ▁model ▁ 3 1 7 ▁in ▁the ▁late ▁ 2 0 0 0 s . ▁ ▁Old er ▁Kit ▁G uns ▁have ▁been ▁replaced , ▁and ▁though ▁some ▁come ▁in ▁larger ▁cal ib ers , ▁they ▁are ▁even ▁l ighter . ▁This ▁is ▁due ▁to ▁adv ances ▁in ▁tit an ium ▁and ▁al umin um ▁construction . ▁There ▁is ▁the ▁Model ▁ 3 1 7 ▁. 2 2 ▁Long ▁R if le ▁(. 2 2 LR ) ▁Air L ite ▁Kit ▁Gun , ▁the ▁Model ▁ 3 3 7 ▁. 3 8 ▁Special ▁Air L ite ▁Kit ▁Gun , ▁and ▁a ▁. 4 4 ▁Special ▁Kit ▁Gun , ▁the ▁Model ▁ 3 9 6 ▁Air L ite ▁Mountain ▁L ite ▁Kit ▁Gun . ▁ ▁These ▁revol vers ▁have ▁al umin um ▁al loy ▁frames ▁and ▁cyl ind ers ▁made ▁of ▁tit an ium ▁( except ▁the ▁Model ▁ 3 1 7 , ▁whose ▁cyl inder ▁is ▁al umin um ). ▁While ▁tit an ium ▁is ▁consider ably ▁l ighter ▁than ▁steel , ▁it ▁is ▁just ▁as ▁strong . ▁The ▁al umin um ▁bar rel s ▁have ▁a ▁steel ▁l iner . ▁ ▁Sn ub ▁bar rel ▁variation ▁ ▁The ▁Smith ▁& ▁W ess