I think everyone covered this quite well, but to reiterate some of this, when a particular recipe designates compression, all is good.
OTOH, if your experiencing a compressed charge and no such designation is made, there are a few possibles that need verification.
1. Check your data, verify that the specifics of the load are correct, bullet weight and the powder being used are consistent with compression.
2. Make sure your scale or measure is throwing the designated and desired charge published.
3. Sometimes it is possible for heavier brass to create a compressed charge, this can often result in higher pressures when compression isn't designated within the published data, or at that place in the charge table.
The only reason I am addressing these specifics is because I witnessed a major catastrophic event the result of a new reloader who misconstrued the conditions that justify and support a compressed charge. In short, this fellow some how thought that a compressed charge was acceptable as a general condition with any powder, thus an extreme over charge was the result. He was pretty badly burned and bruised up, and his very nice and expensive Weatherby was completely destroyed. The root cause was that this reloader took published information completely out of context at every level, therefore he failed to use the published data for the powder / cartridge / and bullet he was loading with.
But all that aside, published compressed charges are perfectly safe, and often produce very consistent loads, at least in my experience.
GS
