What's the barrel length? My old 870 with 28" barrel liked the Rem factory extra full with Rem Duplex 4x6 and my two 870 magnums with a 23" and 26" barrel likes the Kicks tube .665 with Win HV #6. My 1187 likes the Kicks tube as well but with a 21" barrel I had to drop down to a tighter constriction, the .655 diameter. The ported Kicks tube helps with the recoil when I'm shooting the 3.5 loads.