I would fully agree with LTLR on this one. There were many claims that the 257 STW was a 4K round with a 100 gr bullet in a 28" barrel. While I am not saying this is not possible, I am saying its not possible with anything remotely close to good brass life.
In my testing, mainly with Lilja 1-10 twist barrels of 28-30" in length, the 257 STW will get you 3800-3825 fps in a 28" pipe and 3875-3900 fps in a full 30" barrel and those are full tilt loads.
I read some wild claims from a smith with the last name of Ferguson who supposedly made the first wildcat called the 257 Hot Tamale. Unfortunately, the 257 STW was already around at this time and there were no differences of any kind between the two.
He made some claims of 4100 fps with the 100 gr XLC Barnes bullet in 28" barrels. I contacted him and asked him how he was getting this performance and he said it was his chamber and throat design.
Well, I knew he was full of something but could not prove it as he said he was using special barrels to get this velocity as well.
A few years later, as luck would have it, I ran into a guy on-line that had one of these wonder guns. I asked him what velocity he was getting and he said 4100 fps with the 100 gr XLC..... I asked him what his actual velocity strings were over the chrono.. His reply was that he never had chronoed the rifle but it was dead on the money out to 300 yards so the velocity had to be on the money.............
That must have put a bug in his mind though because about a week later I got an e-mail from him, he was not overly happy with his chrono results, 3810 fps I believe it was!!! Over 300 yards or even 500 yards it was close enough at those velocities that be never could tell a difference.
I had to contact Mr. Ferguson after that, there was no reply about his snow job on his customers.
Anyway, if your expecting 4K with a 100 gr bullet, 9 times out of 10, you will be VERY unhappy unless you are using a 33-34" barrel length.
Barrel life, all depends on how you treat the barrel. If you really baby it NEVER overheating it, you will likely see 800 rounds of useful big game accuracy. If you heat the barrel up, you will see half that.
I have never seen an STW get much over 1000 rounds without some serious velocity loss and noticable accuracy drop off as well.