Few modern houses will have concrete block walls to fix to, external walls anyway.
For lightweight blocks, I doubt anything less than a bolt right through, with a plate on the other side, will be strong enough.
A few years ago, a cabinet in Weymouth was stolen by knocking the wall down. I think it was all retrieved, but they hadn't been able to get the ammo compartment open where they would have found over £2,000 in cash.
The owner was the son of a retired police officer.