there is no safety problem with compressing powder if you work up to it, even ball powder.
the main issue is that bullets can be pushed back out of the case, increasing the cartridge overall length in relation to magazine and/or throat length.
this can in part be overcome by leaving the round in the seating die in the press while you weigh the next charge.
serious compression might also bulge the case.
homework will establish how these issues can be dealt with.
one advantage of compressed charges is that bullets cannot be forced further into cases by recoil, thus mitigating the need to crimp, which will destroy brass.
the other advantage is that very low velocity differences come from compression of powder.
the slower burning the powder, and the longer the projectile (barnes), the higher the probability of needing to compress.
the slower the powder, for the same velocity there is less pressure.
many urban myths surround powder, and one of them is compression.
in fact a compressed load of slow powder might well have less pressure than a loose charge of faster powder, while giving higher velocity.
bruce.