[How much does the action expand after shooting 4 or 5 round in a row?]
As posted above, negligable.
[The book i've read doesn't say anything about leaving room for expansion. I'm inletting the reciever and i'm wondering if i should leave room for expansion ]
Not really - But there has to be certain areas left with clearance, both for accuracy and stock integrity (preventing splitting). See answers below.
[The original factory made stock has clearance between sides of action and the sides of the magazine. do I need to do this?]
In short, Yes & No.
The wood of the stock should ideally touch metal along both top sides of the barrel and the entire sides of the action - but not along the magazine sides or front.
The other parts that should be firmly/evenly bedded are:
the bottom of the receiver,
the rear face of the recoil lug,
the bottom/rear 3" of the barrel channel in the area of the barrel re-inforce, and
the entire trigger guard/floorplate metal.
There should be slight clearance at:
the front/bottom/both sides of the recoil lug,
the rear of the upper tang,
the bottom of the barrel (unless accuracy testing indicates barrel up-pressure just in back of the forarm tip is needed),
the front & sides of the magazine,
around both front/rear guard screws, and
the trigger mechanism.
FWIW, there are several good books available, that discuss in depth the inletting and bedding of Mauser-pattern rifles.
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