The Beesley action Purdey is a true self opener, it springs open whether fired or unfired. The H&H system opens crisply when unfired but if both barrels have been fired it needs a little help to get started and then accelerates. I have seen a Boss, where the ejectors push against the breech face, but didn't get a chance to use it. Likewise the wrist breaker boxlock.
The Beesley designed Lancaster “wrist breaker” in both sidelock and body action versions, most definitely falls into the self opener category.
