I really think it depended on which Parish you were from. I have several references as to the men being from Union and Sabine Parishes but only one reference as to it being the "Union and Sabine Rifles". To quote the Minutes of the Police Jury of Sabine Parish in the year 1861 "Acknowledgments were tendered Gov. Moore for his kindness in assuming for Sabine Parish the cost of uniforms and equipment for the Sabine Rifles and to N.H. Bray for equipping the Sabine Rebels". I don't know anything about McArthur but in last weeks historic edition of the local paper it states "in April of 1861 a school teacher from the Toro community named Arthur McArthur organized a company of soldiers named the Sabine Rifles. The company were soon in service as Co. A, 6th La.
After the death of McArthur, C.C. Nash was Commander of this unit. I am sure these men were from Sabine and Union Parishes.
All I can find on Co. B, 17th La. is it was called the Sabine Rebels.