Been shooting the 400H&H since 2011 a .3785H&H action is the one you want as the OAL of the 400H&H is 3.60. Pheroze brought this topic up in another post
http://www.africahunting.com/threads/400-h-h.21018/
You can check there..
Here is some info that I have collected any questions please send me a PM
Remember there is not any known pressure data out there for this cartridge....so this is trial and error so use caution using someone else data please. Start low work up
You can also find good information in Pierre van der Walt's book
African Dangerous Game Cartidge
Been shooting and loading for the 400H&H since 2011. Got the 400H&H bug from Duke McCaa and his son of Gulf Breeze Fire Arms after meeting them at the SCI show 2010. Gulf Breeze is a Dakota dealer and they have been selling 400H&H bored Dakota's for some time.
I have shot numerous animals with the 400 including a Cape Buff in Zim in 2012. Can't say enough about this cartridge other than there is no commercial loadings for this round or SAAMI specs, there are a few custom loaders like Superior that loads for the 400H&H. Gulf Breeze worked very hard to get Barnes to load for the 400 H&H but they stopped short at getting it SAAMI approved perhaps cost? Gulf Breeze purchased all of Barnes’ brass and .411 dia 400gr TSX bullets (would like to get a box or two) they have also aquired .410 dia Woodlieghs with the proper jacket thickness for the faster velocities of the 400 H&H
It will push a 400gr bullet at 2400fps for the magical 5000lbs of energy and send a 300gr TSX down range at 2700fps. Perhaps it is the stock dynamics of my gun but, it's is a very soft shooter and the cartridge feeds extremely easy. My rifle started as a new Win mod 70 in 375H&H, a Shilen barrel in .411 dia was chambered and fitted with irons and a Z6 1x6 scope. So far it seems to shoot everything I have put through it sub MOA.Some of the .411 dia bullets on the market are, Barnes, Hornady, Northfork, CEB, Swift and Hawk. Varget, RL15 or H4895 will get you down range.
Brass..
Been buying it from Quality Cartridge
http://www.qual-cart.com/ , or Midway. 375H&H brass is easily resized I’ve been re-sizing them in the 400 H&H re-sizing die then loading them with a light load to iron the wrinkles out of the neck. I’ve been trimming to 2.840 If you resize 375H&H brass it will be a little short, but the neck is so long in this cartridge I don’t think it matters much.
Primers.. Magnum either CCI 250 or Federal 215
COAL... Dakota Rifles was cutting their 400H&H chambers to load Woodlieghs at an OAL of 3.540. this is what I had my chambers cut for.. The CEB Bullets I load out to 3.60 as they are a bore riding bullet as well as the TSX’s out to 3.60 as the have a very long ogive, if you think you can use some more powder space.
Bullets.. Hornaday.. makes a .411 300gr Spire point designed for the 405 Win good training and varmit bullet
Barnes… makes a .411 300gr TSX,
Hawk ….makes a variety of .411 dia bullets I use these for practice
CEB… I had Dan at CEB turn .411 dia bullets 400gr Solids and 370gr Raptors. These bullets were especially designed for the cartridge demensions I gave them they have them in stock.
Woodliegh…. their Bullets are .410 dia which would not seat in my cases if I had a collet sizing die I could fix this problem. The Woodlieghs are also designed to perform at a lower velocity and I would not use them.
NorthFork… makes a .411 360r SP have a couple of boxes waiting for loading. I am considering this bullet for a possible Buff and Eland hunt.
300gr Hornady and Barnes TSX COAL 3.540
H4895---ADI2206H
77gr.......2633
78gr.......2695
78.5gr.....2683
79gr.......2700
this load has been deadly on elk size game and an honest 300+ meter round. Using the Hornady 300 at 2700fps has become a favorite varmit/pest load as it turns everything into a grey mist..
I started out using the Reloader powders then switched to Hogdons
RL15 300gr TSX COAL 3.540
78gr......2620
I used 69grs RL15 and a 300gr Hornady to fireform 375H&H brass that had been re-sized in the 400H&H die.
400gr CEB Solid COAL 3.60
76gr Varget.....ADI2208.....2400
370gr CEB Raptor COAL 3.60
75gr Varget.....ADI2208.....2400
(I was REALLY hung up on getting 2400 fps and 5000lbs of energy out of this round)...
400gr Hawk Bullet COAL 3.540
Win 760
77grs.......2190...Fun practice load
I hope this helps at least it is a start..
I can cut and paste some Quick Load data that was done for me It was a good starting point but honestly I found it some what lacking but then again I had nothing to compare them to other than my chronograph..
Let me know if I can do anything else for you