After a lot of shooting with different slugs and some home brewed. I was getting the best groups with the Hornaday SST in my 1187 Rem. 20, but for my ML I do like the Barnes for knock down power on deer. I had been thinking about what a hornaday would shoot like if I changed to some Barnes TEZ 250 grain bullets using the hornaday sabot and hull. I very gently with a small screw driver pried the crimp open on a hull to see what the dimensions of the SST bullet were and was surprised to find it was a .452 and the Barnes being .451 but a little longer had me trying the swap. There is a little shim under the SST that is about the difference in height and I did remove this and knurl the Barnes to give it a little more size and grip in the sabot.
You will find that the best way to get the bullet and sabot out of the hornaday is to tap it until it is at the end of the hull and then pull it out with needle none pliers. there might be other ways but this is what worked for me. After sliding the sabot and bullet down the hull and crimping the result was almost perfect.
Now off to the range. The results were a great group and slightly better than factory SST, but about 8".
high. I have not changed the scope yet and will over the next few days be trying more to make sure.
A little expensive at $13 for a box of the SST and about $1 per bullet for the Barnes, but for deer and how much I shoot during the season I can live with this.