Re: M118LR Specs? I got a 1.5 Group @ 500
I don't know if I would base my opinion of a load on a single 3-shot group. Still, I understand the desire and it is all the data you got.
I should note that the links above are to a great article, but the link above is a history of National Match Ammo, M118LR is similar but different.
I would focus on 175 grain SMK's and use a thicker brass, Lapua, IMI, Norma, or shoot and reload some M118LR brass if you can find any. Reloder 15 for the powder. I don't know about the primers, but I would probably use Federal 210M, or these days, any large rifle match primer you can find.
The stickies on handloading for long range in this forum provide an excellent guide. Did your buddy actually work the loads up using your gun? In other words, did he do a ladder test or some equivalent with your rifle or did he just load up some relatively safe generic loads using different components? If he did the latter, the loads really weren't "worked up" for your gun. You can still do some work on the optimal charge length and distance to lands.