Yes, making a big hole through a major blood vessel ends things relatively quickly, but its amazing how long a Cape buffalo's heart can keeping pumping blood even with major leakage in the circulatory system. In Tanzania in 2011 my hunting partner shot a bull facing us, right below the chin at 40 yards with a .458 Lott, the bullet a 500-grain Nosler Partition. The bullet shattered the spine and the bull dropped right there, never moving again, but when approaching the "dead" buffalo, the PH told my partner to put an insurance bullet in the bull's chest. He did, and a spout of blood started pumping out of the hole, the pumps obviously timed to the heartbeat. I immediately looked at my watch, and the flow's rate did not start slowing for almost a minute, when it started to gradually subside, but didn't stop for at least another half-minute.
The heart may continue to pump, but (in the absence of the spine shot in your particular example) for how long of that period would it be up and at 'em, as opposed to walking a circle in wobbly boots, or unconscious? A genuine question, as I've never shot a Cape Buffalo, though I've shot or been in at the kill for more than a couple of dozen of the buffalo we have in the NT. I soon worked out that spinal shots were a much quicker means of putting them on the ground too.
