If we declare a barrel length too far away from 105mm and being "useful" for hunting, we jepordize the shorter barrels.
interesting point.. athough two things come to mind, 1 - i doubt there would be an need to restrict anything for small game like grouse. It's generally believed that grouse you either hit (and they die) or miss (and no harm done). That may not be entirely true all the time, but it's a generally accepted belief. So any restriction on large game wouldn't necessarily have any impact on the overall 'use' of guns in general, and 2 - these aren't going to be ipsc guns or anything

so the legitimate sporting uses that already exist will still be around. And i think we've seen that if the liberals try to come after gun owners, they're done with trying to put 'little' additional restrictions on things, they've moved on to banning whole classes, like all handguns or semi-autos.
I say we go with 4" as allowed by law and negotiate as short as acceptable if push comes to shove.
I'll tell you what my concern is - this isn't going to be a 'negotiation'. It's going to be a sales pitch. We will either be able to convince people or not in a fairly short time. So the need to present a picture that's 'buyable' is important out of the gate.
That's not to say we shoulnd't go for 4 inch guns per se - but the challenge is to try to defeat everyone's arguments out of the gate. One of those is 'handguns are toys for plinking or for cops to shoot at bad guys - they're not for killing game and animals will be wounded'. That's why i like the idea of the 'purpose-built hunting handgun' argument - "these guns are not the plinkers you might have seen at the range, they are mega-poweful super handguns designed to slay deer in their tracks. (look - this one even says 'magnum'!)" You get the picture.
The other argument we'll get is from leo's and CO's who have expressed the idea that when they approach hunters, they can SEE their rifles and know what they're dealing with, but that if they have a handgun it could be hidden or not visible or something and they could get 'surprised' or the guy could 'quick draw' on them.
Now that's just stupid - but i've heard the argument more than once. So to be able to say 'this isn't a 'quick draw' gun, nor is their any chance of someone stuffing this down his pants and you not seeing it' has some value. Obviously some of that could be addressed by law - you must wear your gun visibly displayed and not hidden, blah blah blah.
Now - maybe there's some other ways to deal with that. For the first issue, if there was some 'measure' of killing power that was appropriate it would sure help. right now we use kinetic energy for rifles - which isn't an accurate measure of killing power as we both know, but serves as an effective tool for saying 'this gun has more than enough killing power to cleanly take game out to x range'. If there were some measure for handguns we could hold it up to people and say 'look, this gun is obviously capable of taking deer out to 100 yards cleanly, and that's more than enough range to be an effective and ethical hunting tool'.
Maybe 'momentum' is the answer there - maybe there's enough evidence out there that a 40 cal or larger bullet with x amount of momentum is known to give clean pass thrus on deer and bear out to 100 yards, and therefore that's all we need to concern ourselves with. That way - any gun could be said to be sufficient if it had a minimum calibre and x amount of momentum, regardless of barrel length or the like.
I still believe tho that success will come from demonstrating that these guns are 'differnet' - and the best way to do that is to have something visual. A guy sees a 6 inch or 7 inch gun at the range in 44mag or bigger, and there's no mistaking that for a little 9mm glock or something - it LOOKS huge, it looks like a gun designed to kill deer. Especially with a scope on it - you show that to a ministry official and he'll be saying "wow - that IS a big gun".
The idea is to promote the hunting handgun as a specific breed of handgun that is built and sold BECAUSE it's effective on deer, so there's no reason to think it will 'wound' animals. And when people go online and read about it while they're trying to make a decision, they see that handguns in this class are indeed lethal on big game.
I don't know - maybe the answer is some sort of combination of things, like 'must have a minimum momentum of x, and you must qualify with each gun you intend to put on your hunting att by getting five out of five in a pie plate at 50 yards from the bench' or something - just to prove that anyone going out there will have a suitable tool and can use it accurately so there's no valid claim that people will wound animals.
Or possibly the answer is a list of 'approved guns' (which i utterly hate, because it means forcing them to update it regularly) which the ministry has deemed to be 'handgun hunting' platforms. People are weird - they believe anything a ministry has 'ok'd' MUST be true. If the ministry says 'this is an effective hunting handgun' they'll buy it. But then we just have to make a case to the ministry for which guns are included, and the 'average joe' doesn't have to think about it, they'll just assume any gun on that list is a good deer killing gun and the ministry won't allow 'bad guys' to take out 'weak guns that wound'.
You can see where i'm going with this. But whatever we push, remember, we're not negotiating as much as we are making a sales pitch, so it's got to be good.