Centerfire (no caliber floor until the .221 Askins incident in 1937, then raised to .32).
.45 ACP (both semi-autos and revolvers allowed)
Service Pistol (minimal external modifications allowed)
The first documented service interest in National Match pistols arose in 1920. However, this was limited primarily to reducing the minimum trigger pull regulations and adding slightly larger sights (⅛” sights versus issue 1/10”.)
“Fitz from Colt” (J. Henry Fitzgerald) quickly set up shop at large matches, fitting factory select “match” barrels and larger sights, as well as performing trigger jobs for competitors.
Follow-Up Letter by Crossman (The American Rifleman – Jan. 15, 1921)
Colt National Match pistols commercially introduced. (1932)
Recommended reference if you can afford it – “American Beauty – The Prewar Colt National Match Government Model Pistol” (1999)
The rise of the civilian pistolsmiths (Pre-WW2)
Archibald R. Brinkerhoff was the Jim Boland/Ned Christensen of the pre-WW2 pistolsmiths. Unfortunately, he died in 1946 before Bullseye shooting enjoyed its post-war resurgence.
Brinkerhoff patented a torsion hammer spring arrangement as well as a sear depressor system. Between the two developments, Brinkerhoff could rework the frame to be more user-friendly to shooters with smaller fingers, and safely achieve sub-3 pound trigger pulls without the hammer following.
The drawing of the reworked frame in the first patent is grossly exaggerated, but I hate to think what it would cost for a modern gunsmith to duplicate the frame modifications of the pistol in the article. Still, the concept is rather neat as you could rework the mainspring housing any way you wanted since its purpose is reduced to holding the grip safety and sear spring in place.
Brinkerhoff submitted one of his modified M1911 pistols to the US Army’s Chief of Ordnance back in 1933. However, Ordnance was only interested in Brinkerhoff’s recoil buffer system. The design inserted a spring-loaded plunger into a GI-length guide rod. The plunger would impact the interior of the recoil spring plug when the slide cycled. Oddly, Brinkerhoff never patented the design, and it was widely copied after his death. Another fellow even patented it in the late 1940s!
There is another Brinkerhoff pictured in the book “US Military Match and Marksmanship Automatic Pistols.” From the photos, you can see that Brinkerhoff fabricated a custom magazine slam-pad to match the recontoured frame and stocks. In addition, there is a photo of a custom Brinkerhoff trigger that is fitted with a spring-loaded plunger to reduce the vertical movement of the trigger within the frame. The modern equivalent would be the Castillo’s Custom Actions trigger.)
King Gun Sight (Dean W. King)
While the following patent drawing shows this adapted to a rifle, Berdon performed the same modification to his M1911 pistols.
US Patent #2,046,996 – Trigger pull compensation for firearms
The following post on LTW has a copy of a 1942 vintage article by the early M1911 pistolsmith Jesse Harpe. Note his early self-branded parts, fabricating his own thick-flange barrel bushing, matching spring plug, and barrel links. Also note the number of modifications that are already standard: trigger overtravel stops, reducing trigger play in the frame, tightening slide to frame fit, and fitting the lower barrel lug tight to the slide stop pin.