It sounds like you' ve done good, slee!

I warned you that 100gr of 777 made quite an " impact" ! []

Just keep playing with the powder charge until you find the " sweet spot" for your rifle. You might also just try the 348gr bullets too, to see if they offer any better accuracy (they should need about 10gr less 777 than the 405s).

Good Shootin' to ya!