You're thinking of the 257 Blackbird that's a necked down Blaser. The Blackjack is a modified and necked down 7 SAUM33 nosler would be close but a lot of necking to do. Maybe the 25 blackjack? It is the 7 blaser necked down. I have a reamer for a 6.5 on the 308 norma case changed to 30 degree but it is belted.