This may help your FPE calculation when you select the new/modified spring for your rifle.FPE Formula is Pellet weight (gr) x FPS x FPS divided by 450240.Assume that your H&N FTT pellets weigh 14.66 gr and the rifle is shooting at 710 feet per second.Example 14.66 gr x 710 FPS x 710 FPS divided by 450240 = 16.41 FPE450240 is 2 x velocity of gravity x 7000, (2 x 32.16 x 7000 = 450240)450436 is 2 x velocity of gravity x 7000, (2 x 32.174 x 7000 = 450436)The constant 450240 or 450436 depends on which value you use for the velocity of gravity, 32.16 ft/s/s or 32.174 ft/s/s. There are 7000 grains in one pound. The difference does not matter which ever constant is used for the FPE calculation.FYI the Caldwell Ballistic Precision Chronograph iPhone/iPad APP uses 450240 as the constant value for FPE calculations.
The 98k is the Diana version of the 98k Mauser of WW11 its the same as the 460mag with different dress
or you could just star cutting of coils of the spring until you reach the desired power level your looking for, but don't go to far to where you make the the piston sluggish, another option is to buy a 12lb spring for a 34 it will work in the 460
I sent my 460 to Motorhead for detuning. What a gem he returned to me. What he did is none of my business. But if you want yours done right, send it to him.