I am pretty sure the Kimber 8400 has a long enough action that it could accommodate H&H length cartridges if you modify the action by removing the magazine box(?).

(I don't have one to look at. I know this can be done with a M70; not sure on Kimber).

Anyway if possible you could use a standard old 300 Win Mag or 7mm Rem Mag and seat bullets further out. With the 300 Win Mag you could seat (say) a 180 gr spitzer even with the base of the case neck. This should function through the magazine and still allow longer seating of the heat 30 caliber bullets without i trudug too much into the case below the neck.

You can do the same seating with the 7 Rem Mag.

Of course you could also chamber for something new like the 30 Nosler or 28 Nosler which I am thinking will fit if they feed OK. You will probably need a new barrel a bit sooner than with the 300 WM;and brass is one source far as I know. These may or may not be important issues for you.

If I were doing it I'd build a 7mm Mashburn Super, which keeps up pretty well with any modern 7mm and has favorable bullet seating in a H&H action with heavy 7mm bullets.It is formed from easily available 300 Win Mag cases.

Here is a picture from RCamuglia on here of (L-R) 7mm Rem Mag, 7mm Mashburn Super, and 300 Win Mag. with long OAL seating.I believe that's a 195 Berger in the Mashburn.

Rick built a 7mm Mashburn on a Browning action. He may chime in.The picture gives a comparison. Not sure if you want a wildcat but a Mashburn is as easy as it gets.


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Last edited by BobinNH; 11/28/16.


The 280 Remington is overbore.

The 7 Rem Mag is over bore.