I highly recommend the 140 grain bullets in the 26. The best shooting bullet I have found is the 140 Accubond. The 143 ELD-X has also done well.
The 129 LR AB, and all LR AB bullets, have a much softer lead inside the bullet. It's so soft, if I am not careful during bullet seating, the seating stem of the die will mar the bullet and leave a ring around the bullet. For a big magnum like the 26, I would not recommend this bullet.
Also, forget about shooting any Berger in the 26. I tried most of them, and had poor results with them also, which surprised me.
If you need some match grade 26 ammo loaded right, let me know!