A couple things come to mind...
- the lower the twist rate, the better they shoot heavier bullets. 1:9" will stabilize the lightest (55 & 58gr) .243 pills just fine, as most factory twist rates are between 1:9" & 1:10... Custom/aftermarket barrels typically go lower/faster (1:7" - 1:8"), as the heavier bullets (with higher BC's, that distance shooters want) require a tighter twist to stabilize them & perform well.
- 3800fps for a bullet less than 60 grains is nothing for a .243... Most factory ammo is rated anywhere from 3800 to 3950 fps (Hornady SuperFormance 58gr). It's the pressure that matters, but once you get into reloading a bit more it will become more clear.
- I personally use Hornady 58gr Vmax pills for song-dogs, and depending on the ambient temp my load runs between 3850 (summer) & 3900 fps (winter). At under 300m, it leaves (sometimes big & messy) exit wounds. My barrel twist is 1:9.25", and this load is sub-MOA (~0.75" @ 100m).
What brand of rifle do you own ? I can give you my personal load data, and can show you lots of other data to give you reference (aside from the manufacturers websites).
Good luck, and always start low !
My personal coyote load;
Hornady .243 58gr Vmax
Hornady brass prepped & trimmed @ 2.035"
Winchester WLR or CCI #200 LR primers
IMR 4064 powder @ 43.8 grains
COAL @ 2.620" (measured to bullet tip not ogive, 0.030" off the lands)