Good blood trails come from trauma.

I use mono’s (hornady CX) because I don’t want much meat waste. If you want a heavier blood trail, use a bullet that rapidly expands and transfers that energy to the deer, which causes more trauma.

Sometimes they just won’t bleed regardless if you poke it with a 5.56 or a 50 cal, but the softer the bullet, the more energy You’ll transfer for a greater blood trail.