I think that it is common to have to run a few boxes of ammo through any newly manufactured firearm before the bore starts to smooth out. If they've been shooting cast bullets and leaded up the barrel that will definitely mess with jacketed bullet accuracy.
It is possible that the particular rifle might have a "bump" in it -
basically a bore diameter anomaly in the vicinity of the keyway
for the rear sight, but I think this is a pretty rare event.
My 1.5 year old Marlin 1895 w/ 22" barrel will shoot between
1 - 2" groups at 100 yards from sandbags and a low (3x) power
scope. Someone with better eyes or higher powered scope can do better.
some factory ammo is much more consistent in MV than other
factory ammo. Please provide more info on factory or reloads
and maybe we can provide more useful advice.
When they shoot at the targets, do they wait between shots for
the barrel to cool ? Do the groups tend to form a "string"
(usually running vertically) ? If so, then there maybe some
force/torque exerted on the barrel from the magazine tube
support or forearm.
