If you need to shorten the overall length, it is probably because the gun is chambered for .32 short. It is NOT safe to shoot .32 longs in a .32 short. The long is longer specifically to prevent it from being used in a .32 short chamber because it is loaded to significantly higher pressures. To press the bullet in deeper will only compress the powder charge and cause the pressures to go MUCH higher, dangerously high.
Find the correct ammo for the gun.