I went to the range today to shoot my Daniel Defense AR15 (16" barrel and I believe 1x7 twist) and had a very disappointing session.  Up until now I have been shooting at distance with a custom built AR15 that had a 17" custom Hart barrel with a 1x10 twist for the ton of PMC 55g .223 ammo that I have.  The custom rifle was shooting pretty good with the PMC round as I was averaging 1.5 MOA and hitting steel out to 600 yards (semi-consistently).  I decided to use the Daniel Defense for cheap long distance shooting practice (I also have a 6.5 creedmore Bergara on order) instead of the custom AR (for reasons that are unimportant and too long to explain).  Here is the issue, my Daniel Defense was shooting about 3-4 MOA with the 55 grain PMC round and was shooting only 1.5 to 2.5 MOA with Hornady 75 grain ammo.  What a disappointment.

I am wondering if the barrel on my DD is wonky as 3 to 4 MOA is horrible.  Will a 1x7 twist barrel shoot a 55g round that poorly or is my barrel messed up?

Try a heavier bullet..,.62/69/77 grain versus the 55 grain..1:7 twist is for the heavies....

There's a few other factors affect performance rifle , do you reload?

Definitely stick with a heavier bullet though with that 1/7

The 55 grain will give you decent groups but not precision

I'm curious, what accuracy were you expecting from your DD?  While DD makers fine AR's, most are NOT what I would call a precision rifle.

PMC 55gr. FMJ is just shoot'em up ammo in my mind - get a box or two of Black Hills 77gr. SMK HPBT ammo if you want to see what guns accuracy potential might be.

While you do certainly need to step up your ammo game for the performance you seek, I think both of your rifles are performing abnormally.

One is abnormally good with the stated PMC ammo, which is great for you.

The other, abnormally poorly, which sucks. It happens though...

I'd expect closer to 2.5moa from a "premium" (albeit duty oriented) AR15 using PMC (IME very consistent for ball ammo). However, shit happens and sometimes the house wins. I would NOT expect the 1.5moa you're getting using it in the first rifle.

Try shooting some other ball ammo such as PMC x-tac, wolf gold, American Eagle, or IMI through both rifles and see what happens. If the DD still won't group, I'd suspect something is wrong. Also try two flavors of match or varmint ammo. You can not expect ball to do that great all the time, but 4MOA is too loose for my taste.

Anecdotal side story... my one rifle eats everything pretty much according to its price, ball usually does about 2.5moa. I'm happy with it. It's not a precision gun. It shoots varmint loads near 1.75moa. Cool, mind you it's still a "rack grade" rifle if you will... my brother and I got a batch of 5.56 that would only group 7moa at best. I tried and tried. I cleaned everything, including all copper fouling and fired some WG to foul it up from bare. Still 7moa. Checked my scope... you name it. No cigar... tried my other rifle and it shoots around 2moa... ran it trough his rifle, shoots 2.5moa. I just chalked it up as a loss and sold him my portion of the lot.

Another one is that his .308 absolutely loves some cheap steel case. It will do close to 1.75moa with off brand junk, but hates well reputed PPU and MEN ammo. Barely accepts some common hunting loads.

Moral of the story... win some, lose some...

Make sure your gun is 100% and try some different ammo.

Sometimes some rifles just don’t like some rounds. It happens. Secondly, DD makes a GOOD barrel, but they’re made to be duty barrels that shoot fairly precisely, not the other way around. I’d be happy with anything <3 MOA assuming decent ammo. Third, I’d expect meh results from any 855 clone, and Hornady 75’s have always been hit or miss for me (and a lot of others here). I like them, but they haven’t been nearly as consistent of performers across rifles as SMKs.

Were I you, I’d bench it with a decent optic and trigger, and load up some 77gr Black Hills or FGMM. That’ll tell you what your barrel is capable of, for better or worse.