The purpose of a choke is so the muzzle is somewhat smaller, which ensures gym the pellet has good engagement with the bore at the instant it is released out into the world. (Imagine the extreme counterexample where the muzzle opens up very loose, where the pellet is free to pinball around just before it leaves. No bueno.) It doesn’t necessarily serve to enhance the best achievable accuracy, but it tends to make the barrel less pellet picky. That is to say a choked barrel will generally group a broader selection of pellets at least decently, but don’t count on its favorite pellet doing any better than an unchoked barrel’s favorite pellet. That outcome could go either way. Too many variables to predict it with any degree of certainty, absent of some other knowledge about the specific brand or model in question.
Some OEM airguns use choked barrels, others not. For the most part it doesn’t track with price or brand or any other outward characteristic with enough certainty to be useful, you just have to read the documentation to know whether it does or ask on the forums.
If you have a barrel in hand and want to determine whether it’s choked, push a couple of different pellets through it. If you feel a constriction for the last inch or so near the muzzle, it’s choked. In virtually every case, it will be very obvious. Usually at least a doubling of effort to get the pellet through the choke.
Lastly, note that chokes are really for pellets only. For slugs, a choke tends to negatively affect accuracy. Every once in a while, someone lucks out and finds a slug that groups well from a choked barrel but it’s the exception rather than the rule, underscoring that slugs need to be very dimensionally consistent and matched well to the barrel. They don’t respond well to being sized on the fly with the relatively anemic pressures available in airguns versus powderburners.
