Sure, weight is a trade-off. Too heavy and it's a club. Too light and it doesn't swing well for snap shooting on moving game, and recoil goes up, and recovery time increases. My Leonard built .400 is 10 lbs, 2 oz, and I wouldn't want it any lighter. Heym's new PH/88B in .400 will be 9.75 lbs.

I understand what you're saying about width vs. weight, and yeah, and you're exactly right. There's a BIG difference between the British and Teutonic guns here that dates back to the origins of the design. The British DR "formula" that emerged as the DR developed was very different from the Teutonic designs. The British prized "weight between the hands" - 50% of the weight in one-third of the length - to give a heavy DR sparkling handling characteristics. The Teutonic designs have always prized slimness over weight distribution. If you look at say, a Merkel .465 from the '30s and compare it to a current Merkel .470, you'll see that nothing has changed. At the same time, they never built the quantity of large bores that the British did.

You're right. Compare the action of a Merkel .470 to your Jeffery .450. It looks like a sports car parked next to a U-Haul truck. The action size is the cornerstone of weight distribution. The British guns use larger actions with much more barrel profile to concentrate the weight between the hands. With the tiny German actions, it's utterly impossible to achieve this. The small action requires much smaller barrel shanks which permit much less barrel profile, resulting in a lot more weight in the ends of the gun - anathema to really great handling in a 10 to 11 pound rifle. The trap that many fall into is in thinking that slimness equals great handling. It doesn't.

Of course, not all of the British guns are the same. The Leonard design is more agressive in this regard (it's a big action), while the Webley built doubles, like Kapu's lovely Lancaster, are slimmer. The Webley actions are still substantially larger than the German though. Curiously, the Leonards in .400 are usually 4 to 6 ounces lighter than the Webleys are in .400. At least that's true with the boxlocks, I don't know what Kapu's sidelock weighs.

Regarding the .577s, I've shot them at 13.5 pounds, and it isn't as bad as you might think. I find the .500s more unpleasant.