Re post #8. In general..... The speed of a pellet increases as a the barrel is made longer - up to a point. For a PCP rifle, that effect lasts for about 400mm. Let's just believe that figure for the moment. Some folk argue that if you could measure pellet speed at any instant, then the pellet speed would actually still be increasing after it has left a barrel of 400mm.
Now a pistol barrel is only about 175mm, but the pellet power is nominally 50% of a rifle, and both the velocity and forward air resistance of the pellet are about 70% that of a rifle. In a pistol, the internals have to be tweaked to accelerate the pellet at a fast rate in a shorter barrel - that is inefficient, especially for 0.177 - the result has to be that more air and potential energy is wasted. And that is heard as a noise at the barrel end.
If that air is constrained at the barrel output, then its forward motion and hence energy is highly likely to be transferred, in part, to the pellet.
In terms of whether the pistol becomes a rifle, the major (but very arguable) definition of that being barrel length, could an official choose to count a moderator or silencer as part of the barrel? One thing is certain. If the pellet speed was measured, that could only be done at the accessible end. After the extra bit. Because the catchall law uses the phrase "is capable".
So if it's now a rifle, it's still almost certainly legal, and if it's a pistol it may be illegal. The stock is irrelevant. This subject has been discussed extensively in earlier threads. The lawyers could have a field day!
