I've used the foam plugs, my Colt Hbar match came with a wedge, it makes no difference in accuracy. I had to convince myself of this, the hard way...
A few years back, I was convinced my 243 was stringing vertically, not really stringing but showing 2 separate groups sort of. I found on the web somewhere that bedding the upper to the lower would tighten up groups. So I went to the trouble of bedding that upper to one of my lowers, and I picked the one that is marked 300 saum, it is a complete dpms rifle, kind of rare. Well all that did was create a lower that no other upper would mate up to, so I had to spend all kinds of time carefully sanding the thin layer of JB weld off the mating surface of that lower. Hard to say how much I devalued that rare lower/rifle. Oh and you guessed it, groups didn't change at all. Turns out that upper had a scope problem that was causing the issue.