I use a M1903 with repo 8x scope, but if one really, REALLY wanted to compete with an M1917 rifle, then one could make a very expensive replica of a British Pattern 1914 rifle in .303 British. The CMP rules allow that rifle, but those original British Aldis and Periscopic scopes are rare and pricey museum pieces that are not really available in the USA...but CMP seems to realize this - and I
think that is why they allow the more common Winchester A5 and the repo 'William Malcom 3x" scope - both of which were never used by the British in WWI...
View attachment 8117992
Attached is info from J.C. Harrison's book "P-17 The American Enfield: The Collector's Field Guide Series; Volume Five (2003).
Given that CMP allows the Winchester A5 scope on the M1914, and that the USMC tested 12 prototypes of the M1917 with an A5 scope just after WWI, I suppose one could lobby CMP to allow that configuration, but the ergonomics of that set-up are poor, and a building an M1903 w/ repo 8x scope is cheaper and more competitive, IMO...