Lapuas are some of the highest quality match bullets out there.
The 167 Scenar is not typically chosen for 600-1000 yard competitions (any of the modern 155 match bullets will outperform it). They'll certainly get to 1000 yards and be reasonably accurate, so for "fun shooting" at 600-1000 they'd be find but if you are at all interested in getting good results I'd suggest a better bullet for the task (load up your 167s at magazine length and shoot them at 100-500 yards to your hearts content).
With your rifle you could use one of the modern 155 grain match bullet, or you could use a Berger 185 BT.
I recommend that you do *NOT* use the 155 Lapua in your rifle; it is a poor choice to use in an Obermayer (or other short-leade chamber) that you have (and so do I). It is a very good, very high quality bullet, but it can be quite a fussy bullet to get to shoot accurately and it is also quite unsuited to short throats).
The best 155 bullet I can suggest you try is the Berger 155.5 Fullbore. Load it "somewhat" off the rifling (30 thou is as good as anything), and load it up to full pressure (I use 45.5 H4895 in a Lapua case, Obermayer chamber, .030" jump which is IIRC about 2.950" COAL).
If B155.5s aren't an option for you I would suggest you use old-Sierra 155s (Sierra part #2155). This the the original 155 target bullet and nowadays is one of the very lowest performance (wind drift) 155 bullets out there, but it still works well and and a relatively unfussy bullet. They can still be used to win matches. Load them to magazine length (2.800"), which gives about .015" jump in an Obermayer chamber. Use standard target loadings (e.g. 46.0 or 46.5 Varget, depending on your powder lot and case volume; or 45.0-45.5 H4895).
Another good bullet to try is the new Sierra 155 (part #2156). It is a high performance bullet, in the same league as the B155.5 and the Lapua 155. My personal (and very limited) experience is that they first load I tried was only mediocre (3/4MOA-1MOA @ 100y) and to be honest I have not had the time to bother with load development on it (my B155.5s simply spoil me!). Many of the American shooters use them and they win matches with them. The winner of this year's
Canadian Championships shot #2155 Sierras from 300m-600y and #2156s at long range 800m & 900m. The second place shooter used B155.5s. I think third place used B155.5s and I also think fourth place used Lapua-155s (but his chamber is longer that yours and mine).