GEMSBUCK,
I have worked up a very accurate load with the 450 gr. Barnes TSX. It consists of 72 grns. of H4895, with a Fed. 215 primer. Since the throat of my CZ is rather long, I am able to seat the bullet out, and crimp in the second groove on the bullet, giving me more case capacity, and less powder compression. This may vary with other rifles. This load clocks 2225 fps. out of my 25" barrel, and gives me 1 1/2" groups @ 100 yds. with open sights. Which is to say that the load shoots better that I can shoot it!
The only downside to these bullets(other than the cost), is that they do foul your bore considerably. I have found that the foaming bore cleaners take much of the concern away regarding this problem. Your bore may be smoother than mine, and I hope that is the case.
I regret, I do not have any experience with 400 grn. bullets to pass along. Short of ordering the North Fork versions in that weight, I have not been able to find a supply of 400 grn. bullets designed for anything above 45-70 velocities. If you do shoot 400 grainers, you may find that you have to get a taller front sight, if you are using the irons.
Hope this helps, and good shootin'