When a gun shoots better than you it's good enough.
There is a lot of value to be had from taking this approach (setting the accuracy requirements of your rifle in accordance with the accuracy capabilities of the manner in which you are shooting). I would suggest that the rifle's accuracy be somewhat better than the shooter (perhaps 2X and even better 3X as good as the shooter).
A rusty SKS with a bent barrel is probably good enough to reveal the scores I am capable of shooting offhand.
If I shoot prone fullbore (iron sights and sling), I am a good enough shooter that I will be able to notice that a 2-MOA rifle is causing me to lose points. I won't be able to tell the difference between a 1/2-MOA rifle and a 1/4-MOA rifle though (both are more than accurate enough that neither will be affecting my shots to any detectable degree).
If I shoot F-Class, I will notice that a 3/4-MOA rifle is "inaccurate" to some extent and is holding me back.
how accurate can a TR rifle shoot? As good as an FTR rifle...
Very true, and a good point.
I have to disagree

. If a shooter can hold 1moa and a gun shoots 1moa then that can result in a 2 moa group.
FWIW, two "independent" error sources (the rifle's grouping, and the shooter's grouping) add in a square-root-of-the-sum-of-squares manner. So a 1-MOA shooter firing a 1-MOA rifle will produce 1.41-MOA groups. The same 1-MOA shooter firing a 0.5-MOA rifle will produce 1.22-MOA groups, and with a 0.25MOA he'll get 1.12-MOA groups.
Thats only good enough when you play by yourself

, On the range with other people I need my rifle to shoot as good or better than the others because the proof is in the score for all to see. I wish I could be happy with a rifle that only shoots as good as I do, I'd have saved a lot of money over the years. I've got some 155 amax that I'll try today. I'd like to get it under 1/2 moa with a load that remains supersonic at 1000yrds. Warning shooting at organised events can be addictive & hard on the wallet
The Lapua 155 is a very high quality bullet, but I have found it to be a tricky bullet to tune to shoot well. Once you have, it is as good as the very best bullets out there (after all, it is one of them).
If you can consistently get 3/4-MOA groups, to be honest that's good enough to get on with and shoot in fullbore (TR) matches.
If you want better grouping, you might try an "easy" bullet (e.g. B155.5), you might get good results sooner.