hello everyone i shoot a mathews reezen 6.5 29/70 i use easton flatline arrows with a total arrow weight of 396 grains and i am shooting at 308 fps. my question is can i benefit from changing to a 125 gr head instead of a 100 and how much speed will i lose. also will the lost speed be made up for with penetration.

25 grains is not going to slow you up that much, and yes the penetration will be well worth it. I shoot 220 gn's up front, lots of FOC percentage and good K.E.

back in the 90ties, it was accepted that an arrow was slower than a 30/06. One had to adjust for the slower speed.

3gr of weight=1fps
You may want to look a arrow chart before changing tips, adding that weight would change your spine deflection. Make sure your new set-up will work without having to get stiffer arrows

Well you are good at 5.6 grains per pound if your bow weight is 70 lbs. Also weight forward is good. Dont be concerned with speed its overrated and penitration is more important for hunting. Shoot them both and see what your arrow flight looks like and what your set up shoots better. May I ask what broadhead you have chosen. Happy hunting!