[PGR88]

The objective of the EXACTO program is to revolutionize rifle accuracy and range by developing the first ever guided small-caliber bullet

I know what they mean, but I still find it funny - if you know the damage a .50 round can do, its not exactly "small."

[556x45]

It isnt by a small arms caliber standard. OTOH is tiny compared to all other guided projectiles, fired from artillery. Its hard to imagine how a guidance system could be shoe horned into the thing still using barrels w/ a standard twist rate. Perhaps its so secret not even the designers know it. ;)