I've checked with Blandford Cemetery in Petersburg & the Petersburg National Battlefield, of the 30,000 Civil War Soldiers buried in Blandford, unfortunately only approx. 2,200 were identified and recorded. If a soldier was temporarily buried in Dinwiddie Co. eventually he was reburied in the city which would be in Blandford Cemetery. However, coincidently, their was a Newton F. Gentry that died on the very same day as your John. He is recorded as being buried in Blandford, enlisted at Marion, Alabama, 20th Alabama, Co. H. Taking into consideration records aren't always correct and there were so few to record them back then I'll keep looking to see what I can find. I get out more in the fall to review more resources, I will get back to you if I find anything.