Simon,
I have a couple of M100s in 308. One of them in my safe is my 4 year old grandsons first deer rifle, which he does not know about yet. (don't tell him please). My brother has a M88 in 243 that dad gave to him and he has two M100s, one for himself and one for his son. Through the years we have got to know these rifles very well.
None of them are accurate by my pd rifle standards. But they are minute of deer accurate. We reload for them and that helps. The other thing that I have found in tuning mine, my brothers and several other M100s is the tension on the front screw can have a profound effect on accuracy. I have found that if I locktite the front screw so it is just "snug", I usually find some better accuracy.
I must tell you IMO the M88/100 were not designed for long range hunting. These rifles are a "carbine" style rifle. First of all these rifles have a stock that is for sighting with iron sights, not scopes. Secondly their mechanical design, if you really research them carefully, does not lend itself to accuracy. Thirdly, the trigger mechanism was not designed with simplicity in mind and so does not lend itself well for replacement or tuning to the point where it will become a "light" trigger. I think of them (M88/100) as the next technologic step above the M94 lever action that has very likely killed more game than any other rifle.
We tried to make them something they are not. We put 3-9 scopes on them and tried like h--- to make them shoot to 400 yards. We finally realized they are a sweet little carbine to be used at shorter ranges, on drives, out of stands in woods, etc. I have a 1-3 power scope on mine as my eyes can't focus on iron sights any longer. But I can throw that rifle up to my shoulder and keep both eyes open and chest shoot a running deer as fast as I can shoot a grouse with my shotgun. And if a tree gets in the way, (and they can move pretty fast sometimes) I can get another shot off instantly.
Please understand I am not passing judgement on what you want to do with your rifle.
Just offering some insight as to what we have found over the years.
Jim