Capt, first let me ask if this double is the fastest chambered double rifle you have ever owned? I'd bet it is!

If it is, there is a little thing that is unique to very fast bullets in a double rifle! The faster the bullet, and the lighter the rifle, the adjustments to make change in POI become very minute! A very fast cartridge in a light double rifle is the hardest double rifle in existance to work up a regulateing load for! Even Holland & Holland built a custom double rifle chambered for 225 Win Mag, for one of the magazine writers, and they took a month of working every day with this rifle to get it regulated. If this rifle had been a 450NE with a 480 gr bullet at 2150 fps,in a 9.5 lb rifle, they would have regulated it in a couple of hours. The recoil of the rifle would have been far more forgiveing than a 180 at around 2900 fps.in a 8 lb rifle, thus giveing the regulator a wider lattitude in his load adjustments.

In your post, you didn't say exactly how the rifle was shooting! "Spreading" is not exactly explanatory.

Were the 180s shooting High or low, and were they crossing, or shooting wide. This is more important with this type of cartridge, than with a slower chambering usually paired with a double rifle. The adjustments in speed become very tiny, the faster the cartridge is normally. Where, for example, the 180s were shooting LOW & CROSSED, the slowing down of the load, or the upping of the bullet weight would move the POI in the right dirrection. As Tony suggests, if you use the 220 gr load with the 180 gr bullet, would effectively slow the 180 down, and reduce the recoil, placeing the 180 higher, and reduce the crossing. Just some things to think about!

It makes little difference, because you have found a load that works like it is supposed to, no matter how you found it. You can simply use the 220 gr load, or if you want to use the 180 gr bullets, then try slowing it down, with the load used for the 220 gr bullet. If that is close, the adjustments in podwer charge will likely be in the 10ths of a grain in powder weight,because of the very sensative nature inherent in double rifle chambered for very fast cartridges.

I'd be very interested in knowing exactly what the difference in the load would be when you find a load for the 180 gr bullet!

GOOD LUCK with the 180 gr bullet, but then you always have the 220 gr bullet load that works! That is a lovely rifle, and needs to go to Africa for a full bag of plains game, and a big Leopard!