As a long time .277 underdog shooter out at competition meets. (Nobody , but me ever shows up with a .277 target rifle) I have not ever seen the value in the 135's Logic should have told the manufacturer that 140-160 grain would have been a wiser weight. all I can think of is they were going for the standard twist rifles.
.277 dia. 135 gr. HPBT MatchKing .277 135 gr
.251 SD .488 @ 2800 fps and above
.482 between 2800 and 2000 fps
.440 between 2000 and 1500 fps
.390 @ 1500 fps and below
.277 dia. 150 gr. SBT .277 150 gr.
.279 SD .483 @ 2800 fps and above
.476 between 2800 and 2200 fps
.462 between 2200 and 1800 fps
.435 @ 1800 fps and below
Some of the above poster preferr the 140 sbt. I tumble moly coat the 150's and it increases the BC.
I also use mag primers and either R-22 or IMR 7828 powder.
.458 Barnes X 405 grain - 169.5 grain Wild Cat - 150 moly SBT and the end is a 140 Barnes x