will epoxy bedding improve aluminum block bedding?

Messing with the powder charge can change a whole lot IME.

At .4", you might make things worse, of course, but it'd be downright silly not to find out.

Pat,
The good news is you are consistently hitting sub 1/2 MOA. I would say bedding would help. Devcon is good. Marine Tex is similar and can be found more places. Both are from parent company ITW. The Marine Tex Grey is about the same price but can be bought in a smaller quantity. Marine Tex white had different properties IIRC.
Load testing will probably yield a better group as well. I have a friend that gets his best group at 44.2 & I get mine at 44.3. The only thing in common is they are both Rem 700, .308, Varget and 168 grain bthp match style bullets.
ETA: I got to where I could hardly tell which charge weight to use. I basically made a composite of several groups to decide. OCW helped me.
At this point don't discount yourself as you may make some gains just from fine tuning your shooting. Shooting setup can get you some improvement also. Trigger pull / cheek weld / loading bipod / position behind rifle / rear bag / breathing are all going to be more critical.
Just my opinion, hope it helps,
WNTFW

I agree with WNTFW. There are lots of "free" factors that will have a big effect on accuracy. Start with those first before you start spending money on your gun. By free factors I mean the things that WNTFW mentioned like positioning, breathing and etc.

Keep in mind, .4 inches at 100 yards is less than what a person can even see that far. Nevermind actually being able to hold onto something that small from that far away. I have never calculated it, but imagine what little of a fraction of a degree angle you're already doing.

Good work. You're already ahead of the game.

1/157 of a degree roughly

I consider myself an intermediate shooter. I have the basics down fairly well but am still working on the refinements & consistency of the basics. It is mostly basics anyway.

When trying to discern which groups are better I have found a few things.

I have had to get second opinions from shooting buddies on which charge weight is better. A fresh set of eyes can break the ties. When you get 3 loads that are hard to tell which is better that is a clue as to where you should be.

I have had to force myself to accept the results at face value at times. 44.3 was better than 44.2 for me. Didn't matter that is was higher than most guys loads or the norm. IE it was what it was. I had to go with what was best.

I have had to admit to myself that those 30 rounds were a waste of load development. Example was too windy a day but shot anyway. Not a waste of shooting, just no load development info was not usable.

I hate load development in a way. I'd rather have a good load already. But that is the way it works. No free ride. I bought 500 bullets. I quickly settled on what was the best load to the best of my ability. I was pretty sure my shooting was not helping. I left the load constant and groups constantly shrank. I don't think varying the ammo load would have been conducive at the time.

I read this a few time and I think it really helped find a fast track to load development.
http://optimalchargeweight.embarqspace.com/

I absolutely love shooting .22's and believe it helps. I use mine as a test bed.

Someone had some advise: Free recoil doesn't work on a .308

I had to try it both ways. Too loose doesn't seem to work for me.

Right now I'm really focusing on cheek weld. I taped cut up mouse pad to my stock and did better with it. Now I'm trying to get to a proper piece. I think rifle fit is underated except by more experience rifleman getting good results. With most rifles and shotguns I have found I need to be on the gun.

NPOA - Natural Point of Aim - I definitely believe in it.

I've bedded 3 H-S Precision stockes on heavy barrel Rem 700's. All three shot exactly the same after the bedding. H-S's claims that bedding isn't necessary with their bedding blocks is true. I still do it though.