I can't speak for National Match, but Springfield DID use receivers that originated at RIA as NRA Sporters. I know, because I have one (#1,295,379) that is listed on SRS as an NRA Sporter. If any of you have access to the SRS list, there are vast numbers of NRA Sporters listed that were made from RIA receivers (1,289,000-1,301,000). I only saw one NM rifle listed in this range, a 1,291,514. The largest numbers seem to be in the 1,294,000-1,295,000 range, with smaller batches in the 1,296,000 range and 1,298,000 range.
I didn't think RI receivers were used as NRA Sporters, either, but a quick look at SRS changed my mind!
Chuck, I would disagree on the date of barrels used. I have seen everything from 1926 to 1929 barrels "original" to RIA receivers sent to Springfield.