well it is a 1964 production colt barrel. the only markings on it are the "C" on the barrel extention, and the "VP" in a triangle (verified proof) on the barrel below the sight base. there is NO other marks so it INS'T magnetic particle checked and it dose NOT have the 1-12 mark eventhought it IS a 1/12" twist. Also it is not at all chromed
What I'm describing can be best summed up as it looks as if some one bored out and refinished the lead on the throat of the rifling to possibly restore a barrel that was "shot out" the rifleing dosn't start untill about 1/10 of an inch past the end of the chamber. the head space is correct so thats not the issue
I can't figure out why this oulw have been done I thought if it wasn't made this way then what was done would do to the throat basically the same thing that counterboreing a muzzle would do.
The rifle shoots great so what ever it is it works fine but it just seemed wierd. I first noticed it when comparing the barrel to a 1970's one I had and confirmed it with a military throught erosion gage that there was definatly a big difference. more than the variation between one being plated and the other not would have.
heres and illustration. it's not to scale but it gives the general idea I hope. the Throat I'm talking about is the top one the normal throat is the bottom one.