Re: 243 loaded with hornady 58 gr v max
I prefer to have more than that inside then neck, but you've still got 1/2 caliber burried, so in theory you'll be ok. (.243 / 2 = .125") Just don't handle the ammo real rough or you could get the bullets out of concentric to the centerline of the case/chamber.
From where you are now, you can adjust your seating depth in a little at a time and test for best accuracy at deeper seatings. If accuracy degrades as you seat the bullets deeper, I'd personally try a longer heavier bullet.
Aim small = Miss small