Seem to remember he sat on an elevated platform in the elephant grass which allowed him to see the elephant foreheads sticking out like islands sticking out of the sea but the elephants couldn't see him or each other because of the tall grass. He thought the 256 Mannlicher* or 275* Rigby were plenty good enough for that type of shooting.
From his own book, as well as the writings of others, most of Bell's elephant hunting was done on foot.
He accomplished impressive feats with small caliber rifles for three reasons:
1. He was a phenomenal shot. He was known to shoot birds on the wing with a rifle.
2. He was very methodical. In specific, he took the time to carefully map the position of an elephant's brain within the massive skull and learned how to hit it from virtually any angle.
3. He picked rounds that had excellent penetrating power.