Projectiles for what case?

I have a few large calibers in the collection but very few projectiles. These two were added and I am trying to properly identify. Projectile to the left is magnetic above cannelure. Appears to be tracer? Pink/white substance in base. .55 boyes? British?
O/A- 2.368
Blt/Dia-.510
Wt.- 41.1 g


To the right, fired, with jagged base cut out . Magnetic above crimp in Blt. Is this normal construction? Country?
O/A- 2.265
Blt/dia- .505
Wt.- 44.4 g

Both US .50 cal BMG.
Tracer and Ball (mild steel core) or could be AP ( hardened steel core)
Doc AV

OK thanks, DocAV4901! And as far as the base on the non tracer is it typical to be cut out like that jagged edges? Sorry for weird photo as I have a jewelry loop in front of cell phone camera!!

Philip