I "believe" the Lancaster "Wrister breaker" - not it's real name but was it was commonly referred to - was a Lancaster invention.

By way of design - I believe due to the compression of springs on closing but hopefully someone else can give a better technical description - they are hard to close (for some people.

very similar to closing a Purdey shotgun. Self pening is great until you have to close it. However, that's what you have a loader for !!! LOL