The cleverness of the GI never ceases to amaze me. The following excerpt is from page 143 of Gerald Astor's book, "June 6, 1944: The Voices of D-Day."
"C. B. McCoid, who say his first parachutist at a 1928 county fair, was CO of B Company in the 507th's 1st Battalion and was scheduled to lead his unit in the vicinity of Amfreville, a village west of Merderet.
'One of the skilled armorers of the 507th had devised a modification of the airborne M-1, A-1 folding-stock .30 caliber carbine. By installing a locally procured rod, he made it possible to depress the sear of the trigger mechanism and turn a semiautomatic weapon into a fully automatice one. Those cost was only thrity shillings, or about six dollars. I was delighted to be among the few able to have the modification done prior to the invasion and carry the extra firepower in combat...'"
[i](Note: the crucial thing about full-auto firing is timing. The bolt must be locked before the round is discharged. While improvised modifications may result in full-auto fire, as the one described by Capt. McCoid, it can be unsafe and if not done legally today, 10 years at Club-Fed.)
Vigilantibus et non dormientibus jura subveniunt