Folks are saying that you are not showing the accuracy of a rifle by shooting 3 shot groups. So I don't know if this qualifies by others standards or not. This was three, three shot groups. These were 2 different powders, same bullet. Shot at a mere 300 yards. I think the third of the third was the nut behind the wheel. I shot three, went and marked the holes, shot three etc. I never get my barrel to scorching temp so I don't really know or care what five shot groups do. This is a hunting rifle, I like to shoot once. That said I have shot similar sized 3 shot groups at 400, a little bigger at 5 etc. I have about five different load combinations that are hard to determine a stand out winner. Not near as impressive as the bench guns and custom groups you see but still not bad in my eyes. It is indicative of my Accumarks performance.
The trigger on mine is very heavy, but, I gorilla grip this rifle, and the trigger has no detectable creep. So I left it alone. I would defiantely not change the trigger on mine. Weatherby posts instructions for lightening them on their website if you wish.
If you buy a x-378 of some sort the aluminum bedding block gets smashed and peened over. These must be bedded regardless of what they say about not needing it with this type of stock. The forend of the stock, while flat, is really not designed to bring you back to a flat, level state and a scope level is therefore needed and its use adhered to.
I did the "barrel break in thing". I don't know if it helped but this is the easiest cleaning rifle I have ever owned. But, I have never owned a custom barreled rifle either. I have over a hundred cases, most of which have 4 and 5 ejector marks on them. I lost count of rounds but do the math. That "my good group" posted in another post was at the end of these rounds. Fired cases measure just a touch under 1 thousandth out of concentric on the low side of the chamber. The bolt and action are much less sloppy, in feel anyway than my five remington 700's. Initial firing showed not all of the nine lugs were touching. After 100 they all made full contact. Many say "they can't be putting match barrels on factory guns". IMO just because it wasn't installed by a some guy in some machine shop. In all fairness, most likely, in the right hands, the 1 thou irregularity in my chamber would not be there if "custom". I still can't see how it would be unbelievable that a factory, dealing in $1400 guns could not come up with a $300 barrel for it though. Anyhow, the only reason that I made the purchase I did was that I couldn't get a 30-378 from remington. But I'm glad I did get it and to me it was worth every nickel.
Action. First, in this design you have a flat bottom to ride on, which is a good thing if you look at custom bench rest actions. Then we have a screwed down huge recoil lug that in theory to me would further inhibit action torque since the mounting point is out at a further radius from the bore. Add to that a generous side area of the lug to further prevent this torque. I'm figuring the recoil lug is greater in mass, cannot move, and would serve very well in making a switch barrel rifle. I do not need the thicker match lug or the lug pinning done to perform this same function.
I don't know how they compare to others you mentioned as I have not owned or even looked at any of the others listed.
You can have McMillan build a bench stock for it if you so desire. I had to send them a blueprint, and $500 for the MBR stock with decellerator installed. The tang area does not fit as nice as a 700, but fits.
That pretty much sums up what I know about an Accumark.
Good luck to you