I yet to too see a inline not handle the hornady xtp 240 or 300 grainers.I shoot the 300 xtp and 85 grains of T777 in my inline but I change the factory black sabot that comes in the box.I like the harvester crush rib sabot : I think they mike to .500 and my t/c barrel is tight the factory set -up sabot are a o.k. only if I clean the barrel before loading otherwise they can be hard getting down the bore.I never did ask I hope you don't lube the sabot some guy also swap with t/c bore buttter??????
I would recommend plain spit if the sabot are tight going down the bore.
I would also say to mark your ramrod or make sure you are not seating the bullet too much,I know my setup i only sit the bullet/sabot over the powder never crush it.
I would say some guns shoot better with dirty bores so it something you have to play with my bores like them clean so I swap after each shot nothing more then window cleaner on a cloth jag followed by a clean jag
I hope it helps
The funny part I can load up to 115 grains of real BP in my inlines and handle the recoil with no problem but with T7 my max is 85 grains.
I shot the Qt's before still have a few in the bag,I am not a big fan on them only because they will (most of the time) only have one entrance hole and blood trils can be hard to follow;I shot a huge 8 pointers in Pa. a few years back ran 140 class almost lost him to a poor blood trail.I can say the silver lighting in 300 grain will put deer down were they stand I shot a few large does that never took a step and the holes are large enough to leave blood all over the place.
I also shoot the bufffalo Sb 375 grain HPBT another outstanding bullet and again 80 to 85 grains with T7 in my max:
hope all helps