I ASSUME THIS IS THE SAME CHAMBERING??? NOT SURE WHAT THE RIGBY #2 IS. ??? IF NOT PLEASE DISREGARD.

.450 No. 2 NE cases were $7 each from Bertram last time I bought some. One of the more expensive cases. I would purchase more than twekve if I was you to allow load development ie enough different loads to try at a sitting.

In my .450 No.2 NE (3 1/2" case) I use 105 gr of AR2213SC with a foam filler for a 480 Gr Woodleigh RNSP or FMJ. I would suggest starting with a lighter load. 105Gr works well in my Jeffery DB rifle. I think I started at about 98 grs to 110 grs. 105 grs regulated best. A filler MUST be used as the case is nowhere near full enough and without a filler would be potentially dangerous ie hangfires.

I suggest you purchased a copy of Graeme Wright's "Shooting the British Double Rifle". I have some in stock for sale and can post to you if you are interested. The Bible for shooting these sorts of rifles.

Use a chronograph when test shooting loads. And don't exceed the normal range of velocity expected, ie around 2100 fps to 2200 fps for a 480 gr projectile. The pressure signs won't be apparent on a double rifle and if present the pressure may already be too great. I did not notuce any with the range I mentioned.

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Good luck with your rifle and a great family heirloom. Any more historic photos please post.