Reloading advise for 58g v-max in 243

[warbucks]

Using 43.5gr N140 and 58 vmax , I'm getting 1 hole groups at 100yds, very accurate in my Tikka.

Any idea roughly what speed they will be doing, or point blank range on a 4" kill zone, i am wanting about 300 yds if possible.

Dave (warbucks)