155s, definately. 42gr broke 2700 in the 26" barrel I developed the load for. Start around 37.
175s, maybe. I haven't had much success in getting them to shoot well, but it is doable if your goal is putting lead downrange... who knows... it may be great in yours. I got mucho pressure signs at 43.7 and 2600... id guess max at about 41 or a little less... but watch your stuff.