The last I heard (several years ago) was that if you had the components to fire it (balls, caps & powder) then it was illegal. You could have it as long as it wasn't accompanied by these.
We used to take the pistol to PA, buy the load materials there, shoot it, & return with a pistol only & never had a problem, but that was because we only had the cap & ball without the materials in NYS.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”