Just a comment or two on your stock design. I notice that in your video you are shooting with your head upright, which essentially puts your cheek to the rear of the Monte Carlo cheekpiece on your stock, thus defeating its purpose, which is to keep the stock from slapping you in the cheek when the rifle is fired.

I am attaching a photo of my wildcat .505 SRE, built on a P14 Enfield action. The rifle weighs 8 3/4 pounds, but is manageable to shoot because of the stock design. The photo shows that the stock has a negative drop, that is, the drop at heel is less than the drop at comb. This produces the same effect as the Monte Carlo along the entire length of the comb.

The cartridge, the one in the middle in the photo, fires a Kynoch 570 grain .500 NE bullet resized to .505" at 2150 fps, the same as the 500 NE, and generates identical recoil. It just handles it differently than your rifle.

You might also consider your stance. Your standing position would be good on the target range, but is not very well adapted to heavy recoil. If you shoulder the rifle as you would a shotgun, leaning forward into the recoil and locating your cheek farther along the stock, I think you will find the recoil much easier to deal with.

I highly recommend practice with reduced loads, particularly with cast bullets. You can get a lot more practice in if you don't have to shell out big bucks for the components. I also recommend AA5744 powder for reduced loads. I have used it in a number of applications with my .505 Gibbs and .500 Jeffery (I don't own a .500 NE), and it has proved to be ideal.

To quote the manufacturer, "Accurate 5744 is an extremely fast burning, double-base, extruded powder. This unique powder can be used in a wide range of rifle calibers and magnum handguns. 5744 is characterized by excellent ignition and consistency over a very wide performance range. Low bulky density and superior ignition characteristics make 5744 an excellent choice for reduced loads in many rifle calibers and in large capacity black powder cartridges such as the 45-70 through 45-120 and 50-90 through 50-120. Made in Canada."