How are you going to cut the slot for the bolt handle? Do you have an indexing head or are you going to do it some other way? I plan on making a breech also but I don't have an indexing head. I have a small rotary table and I thought I might use that but I'm always open to suggestion.
That looks really good. An exact duplicate of the Crosman breech. Did you use a small ball end mill in the loading slot to get that radius between the horizontal and vertical faces? I thought I might make one out of 6061 first. If all goes well I'll make another out of steel.
There's no radius. It's just the way the light hits the cutter marks that make it look that way. I wanted to put the radii in and tried to grind them on an end mill but ended up actually dulling the cutter. I was going to use 6061 but I didn't want to buy the material and had the steel anyway. You might end up just using only the aluminum but I don't know how well the bolt handle slot would wear.