Someone else's OAL means nothing to you and your gun. If it fits and functions in your gun, it fits and functions. Nothing else matters.
Newer Remington rifles have chamfered firing pin tunnels and will sometimes show primer cratering at normal pressures.
However, 2.800 is quite long for a 243Win cartridge. If that bullet is touching the rifling, you could be increasing pressures dramatically. QuickLoad internal ballistics software tells me that load is at least 62,000PSI and as high as 70,800psi if the bullet is in the rifling.
If you started at that load without working up to it, you did a very dangerous thing. You should always be starting at listed starting loads or 10% below max, whichever is indicated.
It's not always dangerous to exceed published max loads, in fact many of us load cartridges for which published data does not exist, but it is ALWAYS dangerous to start at high loads. One small mistake could be catastrophic. Maybe you set your OAL wrong (as I did recently) and are creating excess pressure by jamming the bullet in the rifling. Maybe you've got a small chamber or a fast lot of powder, too many variables to list.
Starting low lets you find these things before the pressures reach dangerous levels.
Your friend should also be aware of this fact and if he allowed you to shoot those rounds without working up to them I would never fire another cartridge that he created.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.