I don’t think the ASKMR answer on car length was very definitive. Not really sure what a “striker” is and I know the prototype doesn’t measure car length to the inside surface of the drawhead.
There are 3 common lengths of a car depending on what you want to measure.
Inside Length (IL): commonly used for commercial purposes since it denotes how much room is inside the car to load. On a boxcar iths the length inside the car from end to end, on a gon, its the distance between the ends and on a flat car its the length over the deck. A “40 ft boxcar” is forty feet INSIDE the box. It is commonly used by the marketing department.
Length over the Buffers : this is the overall length of the cars. It is the length over the buffer plates on the ends of the car. It is typically a foot or two longer than the IL. This is commonly used by the mechanical department.
Length over the pulling faces : this is the length between opposing pulling faces of the knuckles. It is the length of a car in a train. It is commonly used by the operating department. It was common for railroads to estimate siding capacity in 45 ft cars. That’s because a 40 ft IL boxcar (the most common car from the 1920’s to the 1960’s) was about 45 ft over the pulling faces.
Here is an illustration of the different lengths and wher they are measured to on an actual car:
Striking Plate. A steel casting placed on the ends of the center sills of freight cars against which the horn of the coupler strikes, preventing damage to the draft gear and center sills.
The drawing makes the the note: “Inside face of coupler knuckle with coupler against striking casting” in regards to total car length which, in this case is a total of 24" less than the length over striking castings.
The definition of Buffer is a little longer but the highlights are:
Buffer. The apparatus applied to passenger cars for the purpose of closing the space between adjoining cars. Equipped with a shock absorbing device similar to a draft gear, the buffer also helps absorb the impacts incidental to coupling cars and in addition cushions and smooths out other minor shocks and vibrations which occur during train movement. The body of the buffer telescopes the platform end framing, its action being controlled by the buffer springs.
