But there are a few discrepancies that I find myself wondering about ....

As you can see, the barrel is longer and thicker than the 88 L/71 on my HL JagdPanther, despite them being basically the same gun, historically.
Now, I know length isn't that big a deal, since a considerable amount of barrel is inside the vehicle, so I'm willing to discount that, but that leaves sheer thickness of both barrel and recoil sleeve. Even the muzzle brake on this replacement barrel is thicker and larger than the one on my JP.
So I got to measuring my barrel. (There's something very few men will admit to doing ... ) and it measures 360mm long, uncluding muzzle brake. This is a reasonable length, if you do the math: ((88*71)/16)=390.5mm.
The inner diameter is also reasonable, being 6mm. An 88mm caliber barrel would have a 5.5mm inner diameter in 1/16th scale, and a 105mm caliber gun a 6.6mm inner diameter. The 6mm of this barrel could just be for airsoft reasons.
... Which gives me pause. My HL JagdPanther has airsoft, and its barrel isn't nearly as thick as this one in external diameter.
In fact, it's the external diameter that gives me the most problems. I have to seriously file away at the old Tamiya Konigstiger's mantlet in order to make the recoil sleeve fit, all the way into the nuts around the recoil sleeve. Though in all pictures of Konigstigers you can see that there's still a small bit of space between those nuts and the sleeve.
So, what gives?
Is the barrel on a HL JP notoriously thin and is my replacement barrel for the Tamiya KT proper scale? Is my replacement KT barrel unceremoniously thick? Was I accidentally sent a 105mm barrel? I don't know of any german 105mm guns of this length that are historically significant enough for small webstores to stock them. Should I just file out the Konigstiger's mantlet down to the nuts and give it a slightly more 'chunky' barrel?
What do?
One thing I have been considering is using this barrel, minus the (very thick) recoil sleeve and just approximate a proper thickness recoil sleeve with heat shrink. Ofcourse, this would mean the barrel won't be able to recoil into the recoil sleeve, but at least it'd look right.