Why did Remington stop productingthe Model 78 Sportsman?

I am the one who asked this question. I am a Remington fan, but I never heard of the Model 78. I loaded some ammo for a friend that owns a model 78 and when measuring the lands if realized that the overall length of the bullet was much longer than rifles I have loaded for in the past. When I looked up the Model 78 I saw that is was only produced for about 4 years and wondered why.