Can't speak firsthand.. but from looking at pics and per
@kraigWY - the Springfields are by far the most popular, along with as you said, Swedes, Mosins.. and from pics Ive seen Garands as well..with K98's, Enfields and such showing up as well but not as much as the before-mentioned. AFAIK, the Nat'l Match versions of '03s/Garands ARE allowed in Vintage Sniper(ie using NM Garand & M1903 NM to make faux- 03A4/USMC Unertl/M1C/M1D, etc.. unlike the regular matches).
Regardless, even in regular matches where the NM versions AIN'T allowed, the '03 competes in its own class by itself, and the cutoff scores are higher. Obviously this is done for a reason, and its hard to imagine that reason is anything besides 03's being on average more accurate. Sights obviously play a part.. but Garands have better sights than 03's IMO and their cutoff scores are lower. M1917 sights are quite good as well IMO along with No. 4 Enfield sights.
It'd be nice to see CMP add a couple more classes; eg a "Limited Vintage - Irons" class in the same vein as Vintage Sniper where you must use old mil-surps with everything about the rifle in stock configuration EXCEPT the sights, with only period-correct non-magnified target sights allowed. Kinda like a "Vintage Sniper - non-magnified" deal(ie to make use of a lot of those Swedes and K31's with diopters).
And then do like a "Unlimited Vintage - Irons" class(to make use of some of those of old '03 target sporterized builds, CG-63 Swedes, old school K98 target sporters, etc) for old school style Match rifles ie must be a mil-surp action but along with vintage style wood stocks, heavier free floated Chrome-Moly barrels(to stay w/in the vintage spirit), and the same period-correct target diopter/aperture sights as used the "Limited" class above. And then of course, an "Unlimited Vintage - Magnified".. basically same rules as the Unlim. Vintage - Irons mentioned before but with period correct optics.. an Vintage Sniper Unlimited so to speak.
Basically, a few classes to allow for all those old ~1920's-> ~1960's pre/non-R700 & non-M70 milsurp sporterized USA Nat'l Match/Euro target builds(and purpose built stuff ala CG63, Kongsberg M59/M67, etc) to compete in cause theres a TON of rifles out there that're exactly what I'm talkin bout. They already got the Unlimited Garand class, but its a TON of work($$$) to do a serious all out Unlimited Garand target rifle so AFAIK ya don't see many Unlimited Garands at CMP matches and AFAIK Garands are the only ones allowed in it. IMO you'd see ALOT better turn out(or at least more opportunities for folks to compete while keeping with the vintage/mil-surp idea and culture of CMP) in the aforementioned classes. Eg: yank off your Unertl from your '03/Ajack from your 41b and grab some diopters.. viola you can now compete in standard GSM matches, Vintage Sniper, and the "Limited Vintage - Irons" class. A ton of CG63's are out there.. yank off the irons and throw on a Lyman 12x.. viola you can now compete in Unlimited Vintage - Irons and Unlimited Vintage - Magnified...etc And as said before, keep the rules somewhat loose to allow as many folks opportunity as possible - long as its kept to mil-surps or in the Unlim. classes, modded mil-surps; and kept to period correct sights and for the magnified class: period-correct optics.
But maybe iits a hair brain idea and I just done had a brewski too many tonight..?