When you use a size or two larger lead pellet in a shotshell, in this case 1-1/4 oz. of #4 lead out of a 20 gauge through a Trulock Precision Hunter Modified choke, you'll get:

1. Less wind drift

2. Less drop

3. Larger wound channels

4. Deeper penetration

5. Rounder shot, as larger lead pellets deform less on initial setback

6. Higher strike velocity

7. Shorter Time of Flight

While penetration in 10% ballistic gel is a good comparison media, ballistic gel is an attempt to emulate soft tissue only, which is exactly what we are not hunting, unless we are hunting jellyfish. The average density of soft, fleshy tissue is not similar to bones, skin, and feathers. Moreover, the anatomy of large mammals cannot be compared to birds, nor can a 1200 fps lead pellet rationally be compared to a 130 or 150 grain bullet. When pigs fly, their anatomy would likely be far closer to a bird, but for now, flying pigs are rare.

When hunting pheasants with one dog, there is a good chance that the vitals are not well exposed, so you will need to break bones and plow through feathers ans skin to get to the goodies. In that case, penetration numbers don't tell the story, for it is the strength of the structure that we need to break, not merely soft tissue. The “Texas Heart Shot” is common on going-away birds, and #4 lead does the job instantly where #6 lead fails to do so. Driven birds are a different matter, but for flushing birds with scant little head, neck, or breast exposed, using a larger diameter lead pellet than what is often the most common can pay noticeable dividends.