ntxt

THis has been brought up several times on this forum and the big bore forum. A search of each will give you a lot of background info.

The ONLY ones I would use are the LaPour and the Timney

Can't say anything about the safety, but I purchased a Timney for my 550 in 416 Rigby. It took me about 30 minutes to install, including adjustments to trigger itself. I think it is a great trigger. I have shot one with an AHR trigger, and it was very crisp and I liked the looks. Didn't take the action out of the stock, so can't really compare the two as to installation and ease of adjustment.
One other pionter...the last time I called Timney it took a few days to get through to talk to someone, so be patient, I think they are worth the wait/trouble, it takes to get in contact with them. Once I talked to them, I had the trigger in about 2 weeks.