There were several interpretations of the .450 3-1/4" cartridge. Many makes of rifles will accommodate the current "standard" .450, which is the same as the .450 Nitro Express.

However, there are older rifles that are made to different chamber dimensions, often tighter. I first encountered this with my Alex. Henry double .450 BPE. I had the same problem of brass not fully chambering.

When that problem arose I contacted RCBS and spoke to the head of their custom die shop. He was very familiar with the problem and asked me to send chamber casts. He said he was sure he had the proper reamer and could make the determination from the casts. I did what he asked and soon received a perfect custom sizing die, which eliminated the problem.

I also have a .450 BPE Holland & Holland. It requires this "small base" sizing die and will not chamber a modern "standard" cartridge. Yours probably was chambered to the same specs as mine.

The same issue exists with the .450/400 3-1/4" cartridge. My Woodward .450/400 3-1/4" BPE double is chambered to modern "standard" dimensions.

Later I acquired my Army & Navy Farquharson single shot in .450/400 3-1/4" Nitro Express. It will not chamber a cartridge sized in a "standard" die. Fortunately, the custom .450 die mentioned above is perfect to size the body of the .450/400 for my Farquharson.

You will need a custom die, and that's all there is to it. I think you should contact RCBS. On the other hand, I am told that Hornady now has a custom die shop. You might get in touch with them.

I hope this helps. It is the solution to your problem. Your brass is fine, it just needs to be sized to proper dimensions. If you are going to play this game we play you can't be scared off by the need for a custom die occasionally!

Curl