I have hunted Phelps a couple of times but found there were just too many people roaming around on horses and foot for my liking. I went way back in along the river, or at least I thought I was way back there, and still had lots of folks out there. I went there once for the dove opener and I never saw that many hunters in one place in my entire life. They do have planted crops and such but it seems to me that Phelps caters more to the fox hound guys.
If you live in Stafford, you could try Quantico. It's huge, but you also have the check in hassles you get at Ft Belvoir. I have not hunted out there in 10 years or so but used to hunt there 40 years ago a lot.