O.K. guys heres a bit more information.
H 270945 - A large P under OFF on barrel
E 288797 - SP on barrel, MP on barrel underside
E 299090 - SP on barrel, MP on barrel underside
E 300423 - SP on barrel, MP on barrel underside
K 318196 - SP on barrel, barrel is serial numbered to rifle
F 320532 - SP on barrel, barrel is serial numbered to rifle
F 323789 - SAP on barrel, barrel is serial numbered to rifle
G 334226 - SAP on barrel, barrel is serial numbered to rifle
K 334495 - SAP on barrel, barrel is serial numbered to rifle
K 335980 - SAP on barrel, SAP on barrel underside, barrel is serial numbered to rifle
H 337539 - SP on barrel
K 337595 - SP on barrel, JJ on barrel underside, barrel is serial numbered to rifle
H 339221 - SP on barrel
H 340270 - SAP on barrel
G 341700 - SP on barrel, barrel is serial numbered to rifle
G 341766 - SP on barrel, barrel is serial numbered to rifle
H 342134 - SP on barrel
H 342868 - SP on barrel
G 343834 - SP on barrel, barrel is serial numbered to rifle
RS 344256 - SP on barrel
H 346196 - SP on barrel
G 346437 - SP on barrel, barrel is serial numbered to rifle
RS 347363 - SP on barrel
EG 352390 - SP on barrel, no markings on underside of barrel
T 353421 - SP on barrel
F Winship cased gun 318042 - SAP on receiver, SAP on barrel, barrel is serial numbered to rifle