Remingtonman_25_06, You might struggle to get enough H1000 powder into the 25/06 case with the 100 grain bullet to get to maximum pressure. Consequently you will struggle to reach 3,250 fps let alone 3,400 fps.
Judging from my lots of H1000, you would have to be able to fit about 63.0 grains into the 25/06 case (with bullet seated) to get near maximum pressure, and with the case capacity you mentioned, I cannot imagine how you would do that.
For the reason above, I did not test H1000 with the 100 grain bullet in the 25/06, but believe it should be ok with the 115 - 125 grain bullets.
My Remington 25/06 cases took 59.5 grains of H4831sc to fill to the base of the neck, (63.9 to the top)and the Winchester 25/06 cases took 60.7 grains to fill to the base of the neck and 65.1 to the top.
Using Winchester cases, and the 100 grain Nosler BT, in my custom 25/06 with Sako L61R action, and Shilen 24 inch SS barrel:
58.0 grains H4831sc - 3232 fps (Max)
59.0 grains Viht N165 - 3342 fps (Max)
My lot of H1000 was about 4 grains slower than Viht N165 in the 25/06 AI with the 115 grain Nosler Bt. ie:
59.0 grains Viht N165 - 3305 fps (Max)
63.0 grains H1000 - 3271 fps (Max)
I did test H1000 in my 25/06AI with the 100 grain BT, and a load of 64.0 grains (100% load density) only produced 3300 fps at mild pressure.
I would suggest you try powders such as Re 22, Viht N165, H4831sc, or other powders of similar burning rate with the 100 grain bullet. Brian.