The coordinates given are for a random spot in the High Rock Town Forest in Needham. Although you are going to the same forest, you won't find any cache at the numbers listed. Solve the puzzle to find the correct coordinates to locate the ammo box. (Closest parking is off Central Avenue at the Horsford Pond entrance.)
You can validate your puzzle solution with certitude.
Mrq vf gur YNFG YRGGRE bs gur nycunorg. Znlor hfr gur ynfg yrggre...
Snyyra gerr