got a chance to shoot some woth sierra 55 gr HP at 100 yards it was shooting 2 foot groups. this was out of an AMD 65 with a 12" barrel 3x9 scope& worked trigger. I also tried some hunting reloads 123 grain .310 hornady the did a 1.5 " group out of the same gun, about the same as the PMC.
I will get back to the sabots when time permits I have some 68 grain boat tail hollow points I will try with differant powders I will try some in a 16" barrel rifle that i have that shoots good.
One thing I did notice was that when I started reloading for these guns was that the rommy chamber has a huge amount of free bore like a 1/4" on the gun I checked. one could seat the bullet was past what the mag would allow and still have space before the bullet contacts the rifling.