Compressed loads are not all the time dangerous. If you will notice in your reloading manuals, there will be a notation by the max load for each powder "C" meaning that particular load is compressed, but is still within the saami limits of pressure for that cartridge. That being said, there are varying degrees of compression. I would err on the side of caution if I heard an extreme "crunch" sound when seating a bullet in a charged case. The more compression, the more powder kernels are broken thus changing the burning charateristics of the powder which in itself can cause a spike in pressure. We all know that a full case is advantagoues to accuracy if pressure limits are not exceeded (100% loading density). Alas, 100% loading density is not possible with all powder and bullet combinations. This has to do with pressure and the position of the powder in the case at the time of firing. In a full case, the powder does not have room to wander around inside the case which is aids accuracy. In a case that is only 2/3 full, the powder has room to wander around so the position of the powder at the time of firing can change, ei powder charge near the base of the case as opposed to the powder charge being close to the base of the bullet. This can cause drastically different pressures which will cause a larger extreme spread which in turn does not aid accuracy. That is why most reloading manuals advise when choosing a powder for accuracy loads, choose a powder that most nearly fills the case for the velocity you are looking for.
Sincerely,
Dave (Bubba) Thornblom
PS: In temperatures in excess of 90 degrees F, watch your compressed load very carefully at the range. If they start to exhibit signs of excessive pressure. Stop shooting them. Save those loads for a cooler day. A good rule is to NOT load compressed loads to the maximum and DO NOT shoot them on days over 100 degrees F.