ok at school we have 7 foot 45 lb bar ,and at my house my bar is only 6 foot ,and it weighs 15 lb. does this make a difference ,when your bench pressing?? ,because at school i can bench press 250 lbs ,but at my house i can only do 240 lbs ,and t feels real heavy.

i dont really understand why i can bench press more ,when im using the bar at school ,but whenever i use my bar at my house i cant do has much.