It will be a challenge to get to 100 FPE at 3000 psi with a 25" barrel but it can be done.... You certainly won't do it at 2000 psi, not even close.... Trying for 120 FPE with those specs will not happen.... you would probably need at least 3600 psi to do that.... If you do go regulated, you will need at least 1 cc per FPE of plenum....Also, a 14" twist will not work with a bullet the length of most 55 gr. ones.... Concentrate on bullets the length of the Arsenal Bowman 47 gr. or less.... In fact, that could be the ideal bullet for your build, at 950 fps it would be 94 FPE, which should be achievable....Do NOT run the Gauntlet tube at 3000 psi, but you know that anyways.... You could use a CrMoly tube of 7/8" OD x 0.065" wall for your build....Bob