Help me understand reverse taper barrel

[Shawnba67]

So I have seen several reverse taper rimfire barrels.
My own thoughts are that it is there to provide "choke".
Is this way off base? Is it more of a harmonics thing?
SECOND QUESTION
How much taper is necasary for any effect?
Specifically could about .100 over a 19" hunting rifle tube be of any use at all? .700 at breeach to .800 at muzzle?
(im a bit bored today)

 

[Tim s]

Reverse tapers have been around for a long time.
Choke, no. Remember most of’em are button rifled which means they are lapped, taper lapped, after profiling.
Some use/used them feeling they tune better, right or wrong.
Most of them are used in sporters primarily because they give you greater length at a given weight which is tough to be 7.5 lbs. all in.
These days not a great manyused for heavier guns.
In a hunting gun I’d imagine the only reason would be weight consideration.