Generally speaking. The draft angle on the bottom of the stock ranges from 2 to 3 degrees. Most DBM's are built at 3*. The idea being you inlet perpendicular to the bore centerline so that the cartridge in the magazine ends up parallel. If the gods play nice the floormetal will lay parallel to the bottom draft on the stock belly.
The trick here is getting the receiver height in relation to showline. If I were solving this problem I'd first mock up an action, DBM, and pillars to get the correct case presentation to the bolt face.
Case presentation: The rule I have adopted is what I call the upside down figure "8". The receiver bore is the "big O" of the 8. The primer of the cartridge is the "small O". The primer circumference should lay tangent to the receiver bore. Doing this presents the full width of the rim/head and provides enough overlap with the bolt face so that the rim does not slip under it during the transition up the feed ramp.
Push feeds like a magazine that hangs onto the cartridge longer in terms of the feed stroke. CRF actions seem to respond better the sooner you let go of it. The body of the case underneath helps to exert pressure on the case being fed so that the extractor claw gains purchase and hangs onto it.
Then I would note the distance from rear of DBM to receiver CL as well as the front. From there its pretty easy to measure the stock and see where your at. If the stock is "fat" you could bed it to showline, sink the DBM, then file/shape the wood back to bring everything flush for presentation purposes. This only works so far though as the grip transition can start to look weird. -Think "guppy belly" stocks used on DG safari guns where the magbox is intentionally made fat.
The alternative would be sinking the receiver a bit and shaving the showline to catch it back up. This too can create issues if the barrel channel is petite and at the tang section. If your parts are grossly out of whack (rare, but it happens) you may find yourself having to hit it from both sides to get it right.
Just measure twice and cut once cause its super easy to go too far and end up with a trigger shoe that contacts the guard bow. That sucks to try and fix elegantly. (so I'm told, lol....
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Hope this helped.
C.
