Re: Is it necessary/beneficial to bed scope bases?
I've never had a base loosen up that was properly torqued. The big reason to bed the base is to try and eliminate any torque/twist on the base from the action/base interface not being perfect.
I've done them two ways. The first being trying differnt single screw combination to try and find one that leaves the other end of the base off the receiver, then bed using that screw only (the others are loosely installed to keep epoxy out and align base). The second is to bed the base using the two inside screws. I haven't had a problem with either. In theory I like the single screw method better, as to me in putting in two screws on either side even the inside ones, you can be potentially twisting the base. The upside is you get good metal to metal contact on both sides of the base.
The best way is to bed the base, mount it and your rings, and then use a set of scope ring alignment tools to verify that the rings are aligned. Usually after bedding the base either of the above ways it's significantly closer than before bedding it. At that point depending on how close it is to perfect I'll lap the rings or mount the scope and go.
people have not bedded bases way more than those that have, and their systems work fine, don't fall off, still shoot true, so certainly it's not a requirement, and with a custom receiver I wouldn't bother with it (though I do still check my rings with the alignment tools).
I guess the bottom line is if you mount everything up, and use alignment tools and it says it's aligned it's all good, I wouldn't bother bedding, this has rarely been the case in my experience with factory guns. If not I'd try bedding the base, and check it again, if it's still only a tiny bit off, I'd lap the rings to get it perfect. If it's quite a bit off I'd try different rings etc.
The argument that the rings or base are machined to perfect tolerances is fine, and I don't doubt it in many cases. The issue becomes once you mount everything up tiny differences show up and things get slightly out of alignment. That to me is why you lap, I'll bed my bases just because in my experience it has reduced the amount of alignment issue, but with factory rifles I've yet to see a base/ring setup from any maker end up being absolutely perfectly aligned using a gauge. Is it necessary....nah you can mount a scope up on a set of rings that's not quite perfectly aligned and be fine, I see it every other day. I'd just prefer it to be as close as possible out of the gate.
Usually with anything so controversial as lapping rings, the fact that there is no clear cut winner and people do it both ways very successfully means either way can work just fine.