The M1s we used had a port installed at the muzzle to restrict the gas, and allow enough back-pressure to operate the piston. Still "bark" pretty well. Needless to say the could NOT be used for a DCM Match...basically a built-in BFA. I guess someone decided that the "ping" wouldn't be appropriate sound at a funeral?
I think only the VFW in Independence KS have these (they loan to the MCL as well). The American Legion here in Coffeyville uses 03's and our VFW (which I haven't participated with) has M1's but I'm not sure if they have to manually operate.
Rummaging through the AmLegion's gun locker, I found they have a very nice collection: 4-M1903's, 4-M1917s (two are chrome plated), 3-Krags, and even 2-'98 Mausers (NO M1's at all). Also, remarkably, a Drum Major's baton - brass and wood, about 4 1/2 ft long......