Just goes to show that every gun is different. I have shot 3 different 1300 with 6 different choke tubes. All the .665 tubes( hastings, tru glo and H.S. Strut Undertaker) shot good to very good patterns as long as you tried different loads to find it's preference. The factory ext. full shot horrible as did the Mad Max in .655.

None of the chokes I've shot liked #4 shot. Maybe a more open choke would work better. Some liked #6 shot and other's liked both #6 and #5 shot.

None of my gun/choke combos liked the lighter H.V. loads. They all liked the heavier payloads. I've never tried the Hevi Shot ammo. Just haven't had a need to.

Hope you fine a combo that works in your gun.