.458 american load questions

[cp3head]

I have been searching this site and the internet and I have not been able to find what I am looking for. I am having a .458 American built and I want to utilize the 450 grain Barnes triple shock X bullets; however, I have not been able to locate any load information for this. Most of the data pertains to the 45-70, .450 marlin, .458 win mag, etc. and the bullet weights seem to stop at the 400 grain level. I would appreciate any insight that you can offer. The intent would be for target shooting and hunting if that matters. Thanks in advance.

 

[cdparker]

Do you know about the 12% rule? Take the difference in weight of either bullets or brass in grains, multiply that by 12% and add or subtract that number in grains from your powder charge; depending on which way you are going. In your case it would be subtract. That should give you a fair start.
The .458 American came along quit a while before the 450 gr. Barnes bullet. That bullet was designed for the .458 Lott. The Lott would be too long for the magazine box with the 500 gr. Barnes bullets.
HTH

 

[ireload2]

There is plenty of data for the 45-70 with 500 grain bullets for strong single shots in Hornady manuals
Same for 400 grain bullets in the Speer Manuals.

Check the data and see if it makes sense to interpolate half way between the two bullet weights.
The .45-70 case has slighly more capacity at 2.1" long but the belted case is designed for higher pressures. Pick out what you think would be a reasonable top loads for 3031 and 4198. Then find someone with Quick load to give you an estimated pressure.
Or give them the powder and bullet weight and let them give you the estimated load at standard pressures. Be sure you use a reliable individual with quick load.
Contact the bullet maker for data also.
NO MATTER WHAT DATA YOU USE START LOW AND WORK UP TO THE TOP LOADS.

 

[watercam]

I found some info via Google. Most said the American is similar to the Marlin 450 Mag. and to use that data to start. Loaddata.com has loads listed up to 500 gr. bullets if you are a member there or want to. Recommended powders were Reloader 7 and 4198. I would think that Reloader 10 might work well with heavier bullets.
According to Wikipedia the case holds about 73 gr. of water.

 

[cp3head]

Thank you to all for your input. Once I figure out loads and velocities I will post back.