The M1903A4 sniper rifles did not have star guaged barrels. They were no different than the normal M1903A3 -- no tuning, no accurizing. In addition, if the front sight cuts show ANY evidence of a sight EVER being mounted, it is not an original M1903A4, but should be assumed a counterfeit UNLESS it has DCM release papers or Springfield Armory verifiable documentation. All M1903A4s had the split receiver markings.
The RA barrel marking is for Remington Arms. Rock Island (RIA barrel markings)ceased M1903 production in 1918 and all parts on hand were tranferred to Springfirld Armory or other rework facilities. The RIA receivers, both marked and unmarked went to Springfield. When Springfield could not meet expected demand for Garands, and the War Dept. felt it needed additional rifles, the RIA tooling was shipped to Remington Arms. Very early M1903 Remingtons are identical to late RIA M1903s.
To speed production, Remington suggested modifications to the M1903. These were approved and became the M1903 (modified) to collectors. These have the round rear sight bases without the lightening cuts. In a further mover to simplify production Remington again proposed to modify the M1903 with many stamped parts and 2 groove barrels. Testing by the military showed they were servicable and the design was adopted as the M1903A3. Smith-Corona (SC barrels) also manufactured the M1903A3. The A3 actually has a better battle sight. Some early SC rifles had 6 groove barrels. Some Remington replacement barrels were 4 groove.
Marine/Unertl sniper rifles are very rare advanced collector items and if encountered, should be documented given the well over $3000 plus price tag. I have only ever seen 2. Only one was documented. The Marine rifles were based upon M1903 National Match rifles with star guaged barrels. These rifles have been counterfeited as have most US sniper rifles. These are just harder to counterfeit due to the rarity of the parts needed.
Before you invest the money in any M1903, especially the more specialized variants like the sniper rifles, National Match versions, NRA/DCM sales rifles, Springfield Sporters, or the .22 variants, buy the Col. William Brophy book "The 1903 Springfield Rifles". Is is $59. Also get the Jesse Harrison book "The Collectable '03" for $35. The less than $100 investment will save you from getting stuck with a "rare, transitional, prototype, etc., etc." put-together or rework. Good collecting and shooting!
[This message has been edited by 700PSS Shooter (edited May 17, 2000).]