I own and reload a number of Ruger's. Some shoot great and some not so great.
First I have a Ruger 77 Mark II 7mm Rem Mag purchased sometime in the mid1990's that will shot almost anything into less that .75 inches. My favorite practice load in Nosler 140 BT loaded in RP cases, WLR primers, and 62 grains of either IMR-4350, or IMR-4831 This load is mild and only gives 2900+ ft/sec.. But this gun will also shoot high velocity loads using 140 Accubonds, 140 TSXs, 160 Accubonds,and 160 TSXs into less than and inch. I have purchase two different stocks to replace the boat paddle factory stock. It does not seem to matter which stock I use it still shoots great.
On the other hand my friend bought a 30-06 Ruger 77 Mark II sometime in about 2003. I tried to find something that would shoot in this gun.After months of trying different loads and after free floating the barrel and putting a Timney trigger in the gun, we were both ready to sent it back to Ruger, since the best groups were in the 2.5 to 3.0 inch range. I told my friend that we need to follow Ruger owner's manual, before sending it back. The manual said that before shipped it, we needed to shoot a number of factory loads and sent the targets along with the gun.
We purchased two different factory loads. One a box of Remington 125 grain bullets and the other a box of Federal 150 grainers. We shot both of these loads and to our great shock and suprise both produced three shot groups of .75 inches or less.
Long story short since that time I have found a number of loads that will shoot less than 1.0 inches for three shot groups. I still do not have the answer as to why this gun took so long for us to find a load. I think that it may have just needed to be shot enough to smooth out the barrel.
I have a number of other Rugers. They all shoot quite well. I am giving you my two extremes.