...if your registration certificate says 'handgun'...and you've put a rifle stock on it, is it not now a restricted rifle?
No, it's not a restricted rifle.
As someone above sez,
in Canada, once a pistol, always a pistol.
Handgun is defined as sumpin intended to be fired with one hand,
regardless of the fact that someone changed his mind
and modded it, put a 2-hand stock, etc.
Restricted rifle has another definition altogether.
Generaly, in Canada (unlike in US) you can put a stock on a handgun.
...AND can a cop now harass you for not having it registered as such??
As a general rule, cops can do ANYTHING (and get away with it too).
In Canada, as long as you do
what you are supposed to do with handguns
(re: storage and transport), you are
probably within the law.
You also should be aware that on a Charger
you may not be able to install a barrel that is less than 106mm
(while on a rifle -
registered as a rifle, restricted or non-restricted-
you
could, at least in theory,
install a barrel as short as you want,
as long as it is a rifle barrel manufactured at that lenght).
However,
the way I read the law, the good news is,
as long as that thing is
registered as a Charger,
I would be able to put a sawed-off
rifle barrel on it,
as long as it is not shorter than 106.
Also,
the way I read the law, I would use only
either OEM Ruger 10 rnds mags
or aftermarket mags manufactured
for 10/22 rifles only (regardless of capacity).
I would
not mod my own mags.
Clear as mud?
In the future, it would be wise that you do not ask
the CGN for definite legal interpretations of the law,
nor you put your complete faith in what you read here.
If the law is a little to confusing for you, then go see a lawyer.