The 6.5 Bullberry does seem to be a fine cartridge. However, I thought you might be interested to know that, after gathering a lot of data, I chose and ordered a 6.5 TCU in a Bullberry bull barrel(20inches).
My view is that the TCU is reportedly a more accurate cartridge; still capable of punching out a deer within 150 yards placing the shot(1000 ft.lbs with 120 gr), and great for varmints with light recoil and blast. Brass is cheap. If I need a lightning spitter I have a 30-06 and a 308.
To me the 6.5 bullet is superior to any other; i.e. sectional density, ballistic coefficient , proven again and again in the field.
If I wanted a powerful, accurate cartridge in the Contender and wasn't concerned about varminting with 100 grainers, recoil etc., I would go , for certain, to the 7-30 waters...hands down.
But, like I said, I don't need a boomer.