Stoner had nothing to do with the SR-15 series of rifles. It is simply an AR-15 variant with certain KAC accessories, and in keeping with product lineage / naming conventions, shares the "SR" designation like all other KAC rifles. For example, the 7.62x39 SR-47 was designed just months ago (well after Mr. Stoner's death), however is packaged in / operates on the original principle he engineered.
As far as Stoner's involvement in the RIS: not sure about that one. I've heard Stoner was against using the forearm of the M-16 as a mounting platform (this is pre- free-floating RAS school of thought, remember). Also, my boss's name (Doug Olson) is the only one on the patent, which incidently is dated the same year as Mr. Stoner's death.
5subslr5:
You are 100%. The LMG (light machine gun) is in fact the Stoner 86. The 96 is essentially the 86 with some mods to the stock and trigger group, among other things. Neither of these systems has any real operational similarity or parts compatibility to the SR-15 / -16 series.
Suggested retail price on the SR-15 M4 is $1550.00. CFI Arms had them cheaper, I think.