Best guy to talk to about that is Bill Shehane at DB supply on BR central website has his link www.scopeusout.com
and (704) 824-7511. He shot a 40 cal (true 40) with custom turned .400 bullets at the first mile match in Ohio last year and first guy to hit a clay pigeon at a mile.
Right now he has either 4 or 5 personal .40 and 408 cal guns and building more for his customers. He has several guys turning bullets.
We were talking last week at the IBS meeting and it is getting very expensive to do that and he does not think 408 is going to take off until some custom bullet maker starts making a good VLD jacketed bullet that is reasonably priced to shoot. He is talking to several about it.