FNB stand stands for Fred N Barnes and the 450 Express is part of a family of wildcats Barnes sold back in the 50's. I have a 404 Express, that is really .416 caliber by Barnes.

Barnes later teamed up with a fellow out of Alaska by the name of Johnson and they marketed the guns as BJ Express.

The FNB rifle was most likely acquired from P.O. Ackley and was made by a student Gunsmith at Trinidad. Johnson made the BJ Express guns.

The 416 Chatfield Taylor is virtually the same as the .404 Express. The Express is just a hair wider in the shoulder and longer in the neck and will not fit in the Taylor chamber. The Express predates the Taylor. The Taylor is made from 458 Mag brass, which is short in my Express chamber. I make my brass from 300 Win Mag or .375 H&H.

I don't have reloading dies for the gun. I just use my universal reloading dies.

It's going to take a chamber cast and bore slug to realy determine what you have.

My Gun is made on a 98 Mauser and is extremely accurate.

Ackley's books on reloading have some imformation on the BJ Express cartridges. I don't have those books with me to look them up.