I used the Factory ported, extra-full turkey choke for quite a few years. It throws a good pattern. I could count on 20 hits in the head/neck at 40 yd. with Win.#4's or 6's. A couple of years ago I got an Undertaker tube and had the forcing cone lengthened. I get an average of about 30 hits at the same range now. I've got one of the older model BPS's with the regular Invector choke system.