Hi JMS,
Not intended as a dig at you, but according to the Lapua website the Lapua Mega's are bonded:
"[snip] The mechanical bonding locks the lead alloy in place, allowing the bullet to achieve up to 97% weight retention."
OK, that's interesting. I didn't realise or had forgotten that. The Hornady Interloc is another "mechanically bonded" bullet. Its no more than a crimp or cannelure of the jacket into the lead core. Both of them (Hornady and Lapua bullets) will shed their cores, and it's more common than many people realise because most of the time we don't recover the bullet. As long as the object of our intentions expires rapidly then the bullet worked.
In contrast, the Hornady Interbond is "welded to the core" according to Hornady. In other words, it is bonded at the molecular level. That's what I meant by a bonded core. Hornady themselves say the Interloc's jacket is "mechanically attached ot the core and in extreme case the jacket can separate from the core". The shot I had on that roe with the MEGA was an extreme case, it smashed along 6-9 inches of neck spine. I wasn't criticising the bullet's performance, I thought and think it performed admirably. But the core separated and I doubt that would happen with a chemically bonded bullet.
I had a similar shot on a massive kudu bull in Namibia in 2005. The bullet was the Hornady Interbond 180gr .308 fired from a .30-06. The kudu was beneath me, down a hill, 200m (230 yards - lasered afterwards). The bullet hit the kudu in the spine in middle of the back of the neck. The kudu collapsed on the spot. A kudu's neck spine is very heavy bone. The bullet pulverised the spine and didn't exit, because it bullet broke up into fragments, but the fragments comprised of bonded jacket and core. Given that it shattered his spine, I'm sure the 185gr MEGA or Interloc put in the same place would have had exactly the same effect on the kudu as the Interbond.
Here's a photo which illustrates the size of that kudu's neck (and body for that matter!)
In summary, I don't think that we should expect 'mechanically bonded' bullets to stay intact on anything that involves anything more than ribs. I'm not saying we should all switch to chemically bonded bullets, far from it. For all of our deer, a standard bullet is fine. There is an argument for using a tougher bullet - one with a thicker jacket - on boar.
-JMS