While looking through my late grandmother's garage, I came across a cigar box with various military caliber cartridges in it. Along with all the other cartridges was a Garand clip with 7 casings Headstamped 53 LC . They have a red filling on the end. Look to be blanks.
What are these and what were they used for?

Those are 30.06 blanks used in the M-1, M1903 or M1917.  The red cardboard in the case mouth is used to hold the powder in the cartridge.  These were used in training, salutes, funeral details, etc.  The current supply is exhausted so Lake City is now making new ones with crimped case mouths.  LC 53 means they were made at the Lake City Army Ammunition Plant in 1953.  Lake City is currently the manufacturer of most US military small arms ammunition.  The plant is located in Missouri.

If your thinking about shooting them, they are corrosive.  Don't forget to clean your weapon real good.

MM