AR-15 accuracy issues trouble shooting

Rab1515 · Feb 29, 2016

I recently decided to build an AR myself for the experience, and ran into some HUGE accuracy problems. I started with ZQI (supposedly 1 moa) 55gr ammo, and then tried 62gr green tip. Both types were shooting 6 MOA groups at both 100 and 50 yards, which is down right disgraceful, considering my .17 HMR will shoot 1 MOA at the same distance. I assemble the upper myself, and wanted to walk through what I should do to make it more accurate. Here's what's on it:

80% lower
Single stage trigger
Mako group stock
Magpul M-Lok rifle length hand guard
Anderson RF 85 upper and BCG
20'' red x arms SS fluted barrel 1-8 twist (torqued to 35#)
adjustable gas block
Nikon Prostaff 4-12x40 with Millett 1 piece scope mount.

What should I do to start trouble shooting? I already tried different ammo weights, should I try a different scope rings? I am concerned that the problem may be the barrel itself, but I want to make sure before I drop in a new barrel.

BradMacc82 · Feb 29, 2016

55gr and 62gr rounds shouldn't be expected to give grand results in a 20" 1:8, hell 62gr greentips - not exactly known to be the tightest flying pills out there.

I'd find some Winchester Match, they use the Nosler 69gr custom comp. pill, should give you better results than what you've already gotten. And they're cheaper and easier to find than FGMM in .223

ashershapiro · Feb 29, 2016

Rab1515 said:
I recently decided to build an AR myself for the experience, and ran into some HUGE accuracy problems. I started with ZQI (supposedly 1 moa) 55gr ammo, and then tried 62gr green tip. Both types were shooting 6 MOA groups at both 100 and 50 yards, which is down right disgraceful, considering my .17 HMR will shoot 1 MOA at the same distance. I assemble the upper myself, and wanted to walk through what I should do to make it more accurate. Here's what's on it:

80% lower
Single stage trigger
Mako group stock
Magpul M-Lok rifle length hand guard
Anderson RF 85 upper and BCG
20'' red x arms SS fluted barrel 1-8 twist (torqued to 35#)
adjustable gas block
Nikon Prostaff 4-12x40 with Millett 1 piece scope mount.

What should I do to start trouble shooting? I already tried different ammo weights, should I try a different scope rings? I am concerned that the problem may be the barrel itself, but I want to make sure before I drop in a new barrel.

Did you check the headspace?

Shazam · Feb 29, 2016

Similar thoughts about the accuracy potential of the ammo.

I have an upper with a Red-X SS 20 inch bull barrel that has not impressed me with factory match ammo or handloads. Maybe I'm expecting too much for the price it cost me. I'm thinking of re-crowning it and see if it improves.

Nodak Kid · Feb 29, 2016

Check optic mount to ensure it is not moving on recoil?

Melnic · Feb 29, 2016

Stock trigger?
Do you have another AR that shoots better?
6 is pretty bad. My dads bushmaster and my Delton shoot 2-3 with cheap ammo @ 100 from bags 1-2 with better ammo.

Is the POI moving around from group to group?
What is the time spacing between shots?
Using bags or some other rig?

Rab1515 · Feb 29, 2016

Melnic said:
Stock trigger?
Do you have another AR that shoots better?
6 is pretty bad. My dads bushmaster and my Delton shoot 2-3 with cheap ammo @ 100 from bags 1-2 with better ammo.

Is the POI moving around from group to group?
What is the time spacing between shots?
Using bags or some other rig?

Stock (cheap) trigger
I do have another ar that shoots much better with the same ammo.
POI in consistent, just not precise.
Using sandbags.

Rab1515 · Feb 29, 2016

BradMacc82 said:
55gr and 62gr rounds shouldn't be expected to give grand results in a 20" 1:8, hell 62gr greentips - not exactly known to be the tightest flying pills out there.

I'd find some Winchester Match, they use the Nosler 69gr custom comp. pill, should give you better results than what you've already gotten. And they're cheaper and easier to find than FGMM in .223

I will try some and see what happens.

outrider58 · Feb 29, 2016

Did you square the receiver face/extension?

BradMacc82 · Feb 29, 2016

How tight in the receiver was the barrel extension when you built it?

Rab1515 · Feb 29, 2016

I did not square the receive face/extension
The barrel extension was snug, but not tight. Slid in by hand easily.
I did not check headspace as the barrel extension came installed with the barrel.
Thanks guys your giving me a lot of things to check.

BradMacc82 · Feb 29, 2016

Squaring the face, if you have the tool and paste already, doesn't cost you anything. You will see improvements if the face isn't square, you just have to address the issue of having exposed aluminum after truing the face, not a large inconvenience.

The fit between the barrel extension and receiver (IMO), should be snug. To the point you need slight force to get the extension fully seated in the receiver.

Green Loctite (I forget the #, Chad would know), will act as a bedding compound. A drop or two goes a long way.

good guy 176 · Feb 29, 2016

I had an entry level Bushmaster AR a few years ago that shot erratically for nearly a year. Talked with a Bushmaster tech and he said to send it to them (under warranty) so they could evaluate the matter. They retorqued that barrel and the problem was solved.

Shot my best ever match score with that piece, a neat 484/500.

Lew--Ranger63

clandestine · Feb 29, 2016

BradMacc82 said:
Squaring the face, if you have the tool and paste already, doesn't cost you anything. You will see improvements if the face isn't square, you just have to address the issue of having exposed aluminum after truing the face, not a large inconvenience.

The fit between the barrel extension and receiver (IMO), should be snug. To the point you need slight force to get the extension fully seated in the receiver.

Green Loctite (I forget the #, Chad would know), will act as a bedding compound. A drop or two goes a long way.

Loctite #620

BradMacc82 · Feb 29, 2016

clandestine said:
Loctite #620

Thank you sir, knew you'd remember. :thumbsup:

TheBulge · Feb 29, 2016

Rab1515 said:
What should I do to start trouble shooting? I already tried different ammo weights

Start with better ammo. 1 moa from ZQI? Not a chance. I would expect it to be more like 4 moa.

Magnumite · Feb 29, 2016

I've shot ZQI out my 20" RRA HBAR ant an Armalite carbine upper and it does no more than 3 moa. With those same guns, Federal 55 grain 223 brown box 100 round packs easily play inside 2" and frequently give me 1"'or slightly less groups.

Barrel or indtall is the culprit maybe?

Rab1515 · Mar 14, 2016

I have re-installed the barrel after squaring the receiver face. I also used Loctite on the barrel extension. I have some better ammo to try as well, hopefully Ill get better results.

Rab1515 · Mar 17, 2016

Range report. I reinstalled the barrel with Loctite as suggested after squaring the receiver face, although it required significantly more torque, I don't remember the exact number but some where around 60#, it required a lot of lapping to get it to that point. Its down to 4 MOA with Winchester target 556, which is the best I could find. While disassembling I noticed the end of the barrel was not crowned. I think that might be my next step before replacing the barrel. Any other suggestions?

Mark75H · Mar 17, 2016

Rab1515 said:
I recently decided to build an AR myself for the experience, and ran into some HUGE accuracy problems. I started with ZQI (supposedly 1 moa) 55gr ammo, and then tried 62gr green tip. Both types were shooting 6 MOA groups at both 100 and 50 yards, which is down right disgraceful, considering my .17 HMR will shoot 1 MOA at the same distance. I assemble the upper myself, and wanted to walk through what I should do to make it more accurate. Here's what's on it:

80% lower
Single stage trigger
Mako group stock
Magpul M-Lok rifle length hand guard
Anderson RF 85 upper and BCG
20'' red x arms SS fluted barrel 1-8 twist (torqued to 35#)
adjustable gas block
Nikon Prostaff 4-12x40 with Millett 1 piece scope mount.

What should I do to start trouble shooting? I already tried different ammo weights, should I try a different scope rings? I am concerned that the problem may be the barrel itself, but I want to make sure before I drop in a new barrel.

Is this barrel marked 5.56?

AR-15 accuracy issues trouble shooting

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