Just curious, why choose the 178 over the 168. They have similar BCs and the velocity of the 168 would be higher, which would help for point blank coyote shooting i.e. 0-400 dead on hold. I am just curious, is the 168 not a good bullet, better put, is it not as accurate as the 178 in an Ultra Mag? I have no problems shooting slower, if it will be more accurate.
I've shot 168 A-Max out of a Rem Sendro in 300 win and they have performed very well. In fact I shot my best group with them. I haven't shot them at anything live over 400 yds but the 275# wild pig at 375 yds fell dead in its tracks on a shot that impacted in between its shoulder blades. In my opinion it would be an excellant coyote bullet. The load I shot was very light though with a muz vel of 2850 with 60.0 grns of IMR 4350. I also shot it in my 30-378 wby (26" barrel)at 3400 fps and 121 grains of w872 and it shot very well with higher powder charges.
I too shoot the RUM and mine loves the 125gr Noslers.It does a nice job on coyotes.With 90gr of H-4831 its running at 3625.It was surprising to me for this bullet to shoot in the 3's,you might give it a try.
How accurate are those 125 grain NP? You can go a little hotter with that load, the book lists a 125gr nosler with 100grains of H4831 listing 3800. Does the slower load work out a little better.
I cant explain this,but the 125nosler shoots as good as the 200 smk.I know,I found it out by luck.Doesnt make sense.This combo of 90gr of h-4831 headspaced to 4thou about 5thou off the lands has repeadedly produced 1/4in or just over it.Yes I can run it faster but it opens up somewhat.92.5gr was 3710 to 3722.I havent pressed any further.[no signs of pressure]This rifle isnt stock.Its a pps model remington which I rebarreled with a 26in shilen match barrel.I also neckturn all brass and size only half the neck with redding s-dies.I use a redding case comparator to check headspace and bullet seating depth.89.5gr of h-1000 with 200gr smk will do about the same.They run a little over 3000fps.The 175 berger with 7828 also does well at times but temperature seems to change things around.My load data is diffrent than yours,the max with 4831 says 95.5gr.Whats up with that?I shot a 5-shot group at the Whittington center at 1000 that measured 8.75,for me thats the best Ive ever shot.OK it was [no] wind I was using a 36 power Leupold.Honestly,I think the brasswork made the diffrence.Just FYI, I have had no luck with Retumbo in 180 to 200.And NO,I tried 125's with h-1000 and it was around 1-1/4 and less velocity.Heck of a muzzleflash though.Probally only burned 90% before bullet left.By the way,this is a great site.