I haven't seen any rudeness. Thanks for so many answers!
The rifle is a Rössler Titan 6 Luxus .308 Win. They don't say
anything about short action or long action. The magazine
is 88 mm = 3.46 inch long.
They have "bolt groups". The .308 Win. is in the bolt group "Standard",
please look at the PDF
Interchangeable Barrel System.
All the listed calibers in my first post are in the group "Standard" which
means that I only have to buy another barrel to change the caliber.
Sometimes a different magazine is needed but nothing else.
That's quite cheap and comfortable for me.
But: Some of the listed calibers have a twist rate which is perhaps not appropiate
for long range hunting. For example 6.5-284 Norma has a twist of 1 : 9".
I would prefer 1 : 8".
Please look at the PDF
Twist Rates.
The following calibers have a twist rate of 1 : 8" = 203 mm :
6.5 x 47 Lapua / 6.5 Creedmoor / 6.5 x 57 / 6.5 x 65 RWS.
I can get any twist rate for each caliber but the price is much higher:
perhaps $1200 instead of $700 for the barrel.
(One important point: The minimum caliber must be 6.5 mm = 0.264" or 0.250"
because it is not allowed to hunt hogs with a smaller caliber in Germany.)
Rössler is using barrels from the company "Lothar Walther" which are
quite good. I can shoot groups of less than 0.2 MOA with my .308 Win.
barrel and I don't want to lose precision when I change the barrel !
So the easiest way for me is to choose one of the 4 calibers
6.5 x 47 Lapua / 6.5 Creedmoor / 6.5 x 57 / 6.5 x 65 RWS.
To choose one of the other calibers I need a good reason
like less wind drift, more precision, more power etc.
Thanks
Jürgen