Re: 22-250 speed
I shot many pd's w/a 22-250 and my bullet of choice is the 52gr a-max.The 1-14" twist is made to order for that bullet in my xr-100.
Barrel life has more to do w/ not overheating the barrel and cleaning it at 40-50 shots downrange.If the barrel is hot enough to feel a little uncomfortable to your hand it's too hot.
I wouldn't get wrapped around the axle w/velocity just get a good balanced load that isn't destroying your brass and pound away ,pd's don't know the difference in 100-150 fps.
Also i'd stick w/the plastic tip bullets ,the 55gr sierra blitzking has the best bc and opens up hard on impact.You could try those if you have a 1-12" twist rate.
Pace yourself and clean the barrel often and you can get 2000 shots of MOPD=minute of praire dog.
Happy Thankgiving to you'all -Mike
AIPAC for president !!!!!!!!!!!!!!!!!!!