for accuracy loads i'd stay away from a boat-tailed bullet if shooting at 100 yards. they can be tough to get the best accuracy from up close. you'll see that the competition shooters will recommend, those who know, flat-based bullets for accuracy out to approx' 300 yds.
i'd forget about IMR 4895 for use with anything but varmint bullets in the .270 Win'; and would think that IMR 4064 would be much better for them anyway. this is because of a better loading density with the slower powder. even so, IMR 4350 would be even better in a cartridge like the .270.
for heavier bullets, like the Match-grade Sierra 135 gr' btsp, i'd definitely try some H-4831 SC, which meters better than standard H-4831.
I use a standard primer, such as CCI-200, to touch off a single-based powder like you are using in a case the size of the .270 Win'. a magnum primer will not be needed and may produce less accuracy.
be sure your bench technique is proper with that rifle. the irregular shape of the Handi's forearm is problematic unless benched properly.
take care and let us know,
ss'