I can't even seem to find a bulletin for the 251 called recruit trainer, do you mean Officer Training?
The recruit trainer for the 251 and the m5 half-truck are not in the game but they are in the files, they are suppose to grant them 5% more armor.
For clarification, their is supose to be 3 types.
Recruit: 5% armor (in game file but not in the game, adds more health to the 251 also).
Officer: Speed modifier works as intended.
Veteran: Grant the M5 the rotation modifier but grant the 251 a 0.01 higher bonus plus 2% more health.