I’ve heard different things from different sources on this.
Some say that the dimensional tolerences and rigidity of the upper will have a noticeable effect on the accuracy of an AR. These people tend to favor CNC-machined billet uppers.
Others say that any effect the upper has on accuracy will be completely eclipsed by barrel quality, ammo quality, shooter quality, and/or enviromental conditions. These folks prefer the conventional forged -A4 uppers.
What do you guys think? Assume that I’m trying for consistent 1MOA/500yd. performance in my build. Will the choice of upper matter?
As long as the upper is in spec, it will not influence getting to your goal of 1MOA accuracy. The largest variable would be ammunition consistency, chamber and barrel, and trigger.
Using match ammunition, a match barrel and trigger, and the limiting factor on group size at 500yards will be external ballistics.
Obviously I am disregarding the ability of the shooter for the sake of the discussion.
I have a Daniel Defense match complete upper that will consistently shoot sub MOA with a standard upper receiver. It does have a Wylde chamber, match barrel and match trigger.
I’m not an accuracy guru…but I don’t think anyone has ever shown a measurable increase in accuracy attributable to one of the thicker/stiffer uppers available. To me that says a lot. Ammo, barrels, free floating and what not have all been clearly shown to be beneficial.
I can’t imagine that a wonder upper would hurt anything, but I’ve never seen anything that shows them to do anything better than a regular upper.
While they may be stronger in structural way, I don’t think that they add to the accuracy of the rifle any, or at least not to any noticeable degree. I do like the look of billet upper and lowers though, especially if they have integrated finger grooves or an integrated winter trigger guard.
I’ve been reading a bunch about precision gas guns while debating whether or not to purchase a bolt gun or upgrade the AR10; the custom guys will tell you that for accuracy in a gas gun, it’s all about the barrel.
A billet upper is stiffer and machined straighter than a forged upper and is worth about 1/4MOA improvement over forged however if you’re using a scope mount like a LaRue, ADM, Bobro etc which stiffen the upper this will likely be less like 1/8MOA or less improvement over a forged upper.
I used to use a VLTOR MUR 1 upper on my 3 gun rifle. It was very nice and smooth with a JP carrier. The things I disliked about it was that it’s heavier than a forged upper, I had to modify my Daniel Defense RIS II rail to fit it, B.A.D. levers wouldn’t fit it.
No B.A.D. lever on the MUR1… Hm… I have that upper on the list for my first build. I really like the convenience of the B.A.D… may have to rethink my strategy here.
Let’s not assume a billet upper is any stiffer than forged. Two things conspire against them - the common use of a marginally softer aluminum alloy, and the actual profile after machining.
Bending tests have shown a conventional A1 upper to deflect less in a fixture because of the upper sighting “handle.” It makes sense a flying buttress design would deflect less as it adds to cross sectional area, and does it further from the centerline of bending, giving it more leverage in resistance.
Comparing A4 billet to A4 forged, the flattops seem to be pretty equal. Forging is a stronger method overall, as the material can be shaped to work more efficiently with less bulk and control of the molecular slip lines that affect bending. The auto industry forges wheels for the same reason - in volume, it makes a better wheel cheaper than billet.
Why LD precision users tolerate billet is to use sidecharger bolt handle uppers at a reasonable cost. Sidechargers allow bolt manipulation without disturbing cheek weld or sight pictures, which a milspec handle will destroy.
“Billet” isn’t a magic bullet that makes superior parts. In the aftermarket, it’s often the cheaper way to make low volume parts. How well it performs has a lot to do with the engineered shape, materials, and treatment more than simply hogging a hunk of aluminum with a tool.
Otherwise we’d all be shooting billet Chinese uppers.
One would think that single shot accuracy wouldnt vary much at all. The bolt is locked into the barrel extension and doesnt move until the bullet has exited the barrel. The stiffness of the upper could impact the optics mount and the zero.
The weight, and the incompatibility with the B.A.D. lever, are what give me pause about a billet upper. It looks like I’ll go with a BCM A4 upper for this build.