Id a Springfield 1903 Mark 1 barrel.

Can anyone tell me how to tell if the barrel on a MK1 is a MK1 barrel? What distinguishes it from a 1903 barrel?

Don’t quite understand your question. A Mk 1 was a standard 1903 Springfield. It was modified for the Pederson Device but the war ended before they were used in the big offensive that was planned. They were mothballed until the rifles were returned to regular service and the Pederson parts that were in the rifle were removed. In April of 1931 almost all Pederson Devices were destroyed. The only evidence is of course the left side ejection port. There is no Mk1 bbl per se as far as I know. My Mk1 dates from 1919 but the bbl is dated 2-33. I found a Pederson cutoff, trigger and made a lookalike spindle for my 1919 bubba rebuild.

Most original MK1 barrels will be dated 1919 and 1920 with maybe a few dated late 1918. Anything later than 1921 will probably be re-barreled.

Thanks for the info, I appreciate it.

I believe there is no difference in the barrels of the Mark I and standard M1903. As M1903rifle indicates maybe by the dates. I believe standard M1903 production was intermingled with Mark I production so both model will have the same dates.