It is my understanding that they Don’t make them anymore? I was in a Local Sport store about 2 months ago and they had 8-10 Boxes of the Hornady Great Plains Bullets in .54 Cal, They have likely had them a Long time, That is not uncommon around here. I have seen Blackhorn 209 Sit on a Shelf at Clearance price of 19 Dollars a pound and Stil not Sale. (I helped Sabotloader Score on a Bunch of this BH 209 )
Perfect Reason to Start Casting your own Bullets Get yourself a Lyman Plains Bullet Mold!
If Lyman no longer makes/sells the bullets or if they no longer offer the mould, the Lee R.E.A.L. is a similar design. The mould can be had for 20 bucks at Midsouth and about another40-50 bucks for a furnace and you can make all the bullets you want.