Mossberg 500 rifled barrel, strange accuracy

[don421]

I have a new 12ga. fully rifled barrel/integral scope base, for my Mossberg 500. I'm using winchester platinum supreme sabots. On a cold barrel shot the the accuracy is great at 50yds. A second shot from a hot barrel will be off 4 inches. If the barrel is allowed to cool for a couple of minutes, the next shot is dead-on again. The winchester rounds are 1700fps and develop a very heavy recoil. With time allowed to cool the barrel, the shots will cloverleaf at 50 yds. Should I try different make of sabot? Please help. Don