I have a Lawrence titanium mod on a Mauser MO3 in .300 winmag. Excellent piece of kit. It's an over barrel mod so keeps everything as short as can be, and he has cut and rethreaded my 6.5 x 55 barrel so it can be used on both barrels. That's what you get when you deal with someone in the UK who you can visit - flexibility.
Not the cheapest, but I've had it for about 6 years now. Also no maintenance required.