Brooks

Degoins is refering to my 75% rule.
I cannot take credit for "inventing "it, but i do take credit for "rediscovering" it.

Here is the "75% Rule".

Develop the load for you double in the normal way using the standard full weight bullet, in your case of the 450/400, 400 grains.

Then take a bullet that is 75% the weight of the original bullet, again in your case, 300 grains.

Shoot it with the same powder charge. You might have to tweek it a few grains up or down, but you should be able to fine a load with the 300gr bullet, that hits to the sights and regulates well.

Velocity should be around 2250 to 2350fps depending on what powder charge your gun likes with the 400gr bullets.

This 75% Rule has worked on several 450/400's both the 3" and the 3 1/4", 450 Nitro and 450 No2's, 470's etc. The bullet does not have to be EXACTLY 75% but the closer the better.

I have a 450/400 3 1/4" double. The 75% Rule works for mme with 300gr. Hawk bullets and with 300 gr Barnes X bullets. My double used bullets of .408 diameter.

I have killed a pig with a 400gr Barnes X, and a 300gr Barnes X, both with excellent results. Neither pig took a step.

See if Barnes will make you some 300gr X bullets in the diameter suitable for your rifle.

When not in the Condor Zone, and for testing the 75% Rule in your double, see if Hornadays 405 Winchester 300gr bullets are the correct diameter for your double.

If not just use the 400gr X bullets.