Hello, everyone. Well, it looks as if I have gotten ahead of myself..I ordered new Hornady .450/.400 brass & a set of full length RCBS dies for the Watson Farquharson. Dies arived yesterday..the Hornady brass wouldn't chamber fully..lacked about 1/2". Full length sized brass...still no-go. Used die without shell-holder in arbor press, pushing case in until rim touched die mouth..press out with rod. Still wouldn't chamber fully..Next using a wood dowel, I tapped case in chamber until it bottomed out solid..again wouldn't go in that last 1/2" or so. Case marked about 1" down from shoulder & neck very bright.
I spoke with dealer I purchased from..he said he knew original owner had shot it quite alot, said he would try to obtain some fired brass from it for me. He said this is a common problem with early British ctgs. I am thinking the newer Hornady is alot thicker than original Kynoch..might have to neck ream/turn to allow cast bullet shooting. Bore slugs right at .411"
Probably have to have custom sizer die made..has anyone else had this problem? Thank you!

Are you sure it is a 450/400 THREE inch??

Could it be a 450/400 THREE AND A QUARTER inch??

Try this, turn a case around backwards and press the rim of the case into the rim cut in the back of the barrel.
Does the rim go in flush?

The 3" rim is a lot thicker than the 3 & 1/4" rim.

Hello, N E 450 No2. I'll try rim fit..but the case is still chambering short of head by about 1/2". The rifle is stamped Cordite 60 400Max, and above this is .400 EX. I don't have cerosafe..did do a chamber cast of a .255 Rook rifle using pure beeswax..surprised at how tight casting was in there..not too good for "miking" but for finding length should be ok. Thanks for reply!

Hello, N E 450 No2. You were spot-on..got to thinking of how that .450/.400 bottomed out solid in there..but 1/2" short. Tried an old original .450/.400 paper-patched(copper-tubed!) 3 1/4"..fit like a glove!
This morning, I made a chamber cast..it's the 3 1/4" case! Brl. marked L.H. side, 400 EX
under this is Cordite 60 400gr. Max. Also, all my books say groove dia. is .405" to .408" in this chambering..mine slugs right on .411"
Told dealer..he's embarrased..just prooves you must check for yourself to be sure.
One lucky thing..Hornady makes .450/.400
3 1/4" brass..called & verified dimensions from my casting..they should fit fine. Thanks again!

First rule of buying a Vintage Double Rifle. Check to bores. Then you check bore caliber and you cast the chambers. Wide variety of bores in the 450/400 3 and 3 1/4 class doubles. My 450/400 3 inch is .408 and I know of .411s as well. You can't tell unless you slug or mic the bores.
Also get you some Imperial Sizing Die Wax. That paper thin rim tears if you get a case stuck in a die. Been there done that!

Hope you enjoy your "new" double!

Glad I was able to help.

Yes definately get some Imperial Sixing Die Wax, it is now qalso the same as Redding Sizing die wax, except the redding is green colored. Nidway USA has it in stock.

If you barrel is .411 after you work up a load for the 400gr bullet, try some Hornady 300gr bullets for the .405 Winchester.
They are great for deer and pigs. Just start out using the same powder charge as the 400gr bullets, and then adjust up and down if necessary, watching for pressure signs.

Thanks guys, for helpful advice. I do have the Imperial..and even something better for the real tough jobs..Corbin swaging lube..just a tiny bit goes a long way.
Once I get all the copper out, I plan on using only cast bullets..300gr. to 400gr. plain base..hoping I won't need to go with a gas check design..only after mild accurate target loads. Has anyone had any experience with cast bullets in these? What powders are you using? I have read & re-read Graem Wrights Double Gun book..Thinking 4759 would be a good start. Thanks again!

Did you slug the barrel all the way thru?
Sometimes they used a taipered bore and the muzzle will be smaller than the breech end.

Hello, Mike Brooks..Tight all the way to breech.
Funny thing about that rifling..7 narrow lands..but the grooves are tapered on a circular plane..shallowest point right next to a land..tapering down to maximum depth at side of adjacent land..viewed on end looks like a ratchet..ratchet rifling.