As some of you are aware, I have a 416 Ruger built on a P14 action with a really tight bored TSE barrel.
I have been having trouble with it not getting the speed I thought I would get from a 400 grain bullet.
After some discussion with Daryl here, I had the throat lengthened out to 0.375", from about 0.185".
My next job was to give it a fire-lap, as the barrel is full of tool marks and fouled really badly.
Last weekend I put 20 rounds of fire-lapping through it, two different grades of paste, cleaning between each ten rounds. A borescope inspection before and after revealed a real change in the amount of tool marks present.
Today I shot some 400 grain Taipans with AR 2208 (Varget), long story short, I got up to 70 grains of it and had the 400 grainers travelling at a touch over 2200 fps. 70 grains was the highest load I had today, as I wasn't sure where to stop. In any case 70 grains showed a nicely rounded primer still, so I'll try a bit more in coming weeks, although I'm not sure I need anymore than 2200 fps anyway?
Two lessons learned for me today, fire-lapping works, the barrel fouled noticebly less, requiring a quick clean-up instead of days like before. I fire-lapped using Trailboss and cast lead projectiles BTW. The other thing I learned is that the longer throat absolutely let me get some more speed from the Ruger without undue pressures, and actually improved the accuracy as well.
I'm now back on the "Happy Track" with the 416 Ruger.

Here is a photo of a local vistor we had on the range today, they don't seem at all worried about being on the business end of a rifle range, we closed the range while he and his mate wandered all over the range and eventually left.
To be politically incorrect, I did really wonder what a 400 Grain Taipan would have done, not that I would have.