If you shorten you will need imo a faster bullet to use up the powders in the lenght it travels up and out of the short barrel.
I reduced my 308 down to 16", and it shoots 150g @ 2700fps, and once I found the right load, it shoots better than I can.
Which model Laurence precision titanium you got as I got the neon model which does Nothing for soundJust got a DPT Duralium over barrel,its very good so far,also have a couple of Lawrence Precision Titanium over barrels which are also very good...........