Reading through out the CMP forums and even the descriptions between the rack, field and service grades the most outstanding difference between them seems to be muzzle and throat wear.....my 1942 service grade SA is overal a nicer looking firearm but the 52 SA I have has it beat in both muzzle wear and throat by a friends gauge also the crown on the 52 is minty but the overall condition it looks rougher. both have newer barrels 42 has a 57 I believe and the 52 has a 55 dated barrel or maybe the other way,,,,,anyhows its late and Im not remembering well.
personally if I where collecting on the manufactures I would not hesitiate to purchase a win from the CMP. You will not find one anywhere else unless through a friend or a fellow shooter in better shape for anything close to that @ a FFL dealer. 98% of all the garands I have looked @ at gun shops under 1500.00 are rack grade @ best. The others are so over priced I couldnt even tell you what they where cause I dont bother looking. The ones in between tend to be rack grades refinished.