Jim, look at the Barnes TEZ ML bullets as a option. This is the bullet I hope to use in my bolt gun project.
The 250gr version is 1.090 long, so about .150 longer than a 250gr FTX. Not sure what's left in the case for room with the powder your using, but just a idea.
another option is the 250gr Bonded Shockwave ML bullets, same profile as the FTX so in theory should fly the same.
I'm Barnes or bonded anal when it comes to hunting big game, sure they will cost a good bit more but still the cheapest part of your hunt.