Lack of accuracy AR 16"

[kamikaze1a]

After working out some loads for my newly acquired AR, I have come to the conclusion that the lack of accuracy must be hardware. I got it in a trade for a handgun and thought I was getting a great deal but beginning to wonder if the previous owner could not get it to group either so traded it. It has a RRA receiver and a 16" SS barrel of unknown origin. The barrel is part way fluted and was told 1/9 but never bothered to verify...yet.

I can shoot great groups with my bolt action hunting rifles so I do not think it is me but this is my first tactical rifle and keep reading about others with minute of angle from their's. I tried working on the original creepy, heavy trigger but eventually got a JP when lightening/smoothing the original did not help. After loading various loads with various brass, bullets (55-62gr) and powders with poor results, I surrendered and tried store bought ammo, which gave me the same sort of groupings. I'm getting about 2-3" at 50yds and minute of paper plate at 200yds. This is from a solid bench off of bags using 1X3 optics mounted solid. I got to admit that all my other rifles have higher magnification but 3" at 50yds with 3X convinces me that something is just not right.

Should I remove/reseat the barrel? Or where else should I look? I'm kind of wondering how well it was assembled. One of the first things I had to do after acquiring was reposition the free floating handguard because it was not mounted correctly...

[Beretta Lover]

I hate to say it but its probably a bad barrel, maybe a bad crown on the barrel?

If you shot factory ammo through it, and its bad ou have removed a bunch of variables already

ALso has anyone else shot the rifle? My guess is the barrel was manufactured with worn out equipment and has very shallow rifling or the bore is oversized.

You could swap uppers and remove any problem with the lower from the equation. Also make sure your sights or scope are cranked down.

There is a pretty well known AR manufacturer that had a bad run of barrels (I wont say who they were). The guys I know that got bad barrels sent them back and they were replaced.

If you find out it is in fact the barrel, you can get preety good deals on generic 16 in barrels on CDNN, Midway, Cheaper than dirt and Brownells from time to time.

I have seen 16 in non chrome lined GI profile carbine barrels for $100. Fortunatley just about any AR barrel is going to shoot close to MOA, except if they were made bad and this is pretty rare,

Benny Hill who is a forum member/vendor would be someone you might want to PM here

[benny hill]

Does it have the factory plastic hannguards on it?

[Vlad]

Double check your optics and mounts. Then triple check. I have a AR that used to shoot minute of watermelon, despite me making sure the scope was working right and the mounts were rigid. Apparently they still weren't, I replaced the scope and mounted the new one in a SPR-E, and like magic the guns shot better.

Try iron sights?

[kamikaze1a]

The barrel was suspect to me too. Was hoping the install could have been messed up. I had considered the crown too so should have removed the flash hider and checked... Will do that when I finally get around to confirming the twist rate. Thanks!

As for the forend/hand guard, is a free floater. YHM quad...not necessarily my choice, it came with it but I'm starting to like the picatinny rails for stuff like vert grip/bi-pod mounting...

Re; the optics, it's a flat top so have not tried iron but I have tried other optics as well as another mount but never with magnification higher that 4X because I kind of like the 1X option... Not had any beau coup bucks mounts or rings either but always good solid one piece mounts and it always grouped about the same. I had wondered if the low magnification was the cause but the groups at 50yds pretty much convinced otherwise.

So, unless something comes up, I might start shopping for a new barrel. Probably not going for a megabucks barrel, just something reasonable that will do the job. Probably will stick with a 16" (maybe 18) and the twist is not locked up yet but will probably shoot mostly 55gr so might stick with 1/9... Any suggestions?

[Vlad]

Before you spend money, also have someone else shoot it. You never know, sometimes the wrong combination of parts screws with the shooters. Also when you repositioned the handguard, are you sure that everything was left tight? You may want to check the barrel nut is at the correct torque.

[CocoBolo]

For comparison my Academy store bought Bushmaster shoots nice groups at 50 yards about an inch, with PMC Ammo. Wolf ammo tends to spread a bit. I did work up reloads with BLC(2) and found that POI and grouping can be destoryed or created with a couple .2gr either way.

I didn't see it but if it has a compensator try shooting it without the comp, all it takes to send those bullets into orbit around another solar systems is just a whisper of contact that might not even be visible to the naked eye. I had that with my open gun.

Swaping optics was my first guess but you did try that. I have had jumping cross hairs before.

Best guess a wanna B smith aka metal mangler fit the barrel and bolt assembly.

I am very intrigued with Benny's response, I can't wait to hear the punch line.

[Dan Sierpina]

What are the components you're using for your handloads? Try loading Sierra 52 Match Kings over 25-25.5 grains of H335 if you have the powder. Remington 7 1/2 primers work very well with H335, again if you have them or can get some. 62 grain bullets are generally poor quality for shooting groups, most 55 FMJ's are also of questionable quality. Garbage in, Garbage out.

[cas]

I had a rifle where the barrel nut was so loose the FF tube rocked back and forth. The gas tube was the only thing keeping it from unscrewing, that silly rifle shot great. I never put much stock in precise barrel nut torquing after that.

Do you know the person you got the rifle from? Could it have been a blaster with a million rounds through it and never seen a cleaning rod? (or just the opposite, someone who JB'd the hell out of it)

[kamikaze1a]

Before you spend money, also have someone else shoot it. You never know, sometimes the wrong combination of parts screws with the shooters. Also when you repositioned the handguard, are you sure that everything was left tight? You may want to check the barrel nut is at the correct torque.

The forend was screwed too far in and touching the pivot for the lower. The forend nut was locktited so I heated it up and back out the forend a half a turn to clear the receiver pins. Never actually removed it but also never checked the barrel nut. From a rest, I have confidence in my shooting but letting someone else pull the trigger is easy enough to do. I'll give that a shot.

As for the previous owner, I don't see him at the range anymore and have been watching for him because I wanted to ask how the barrel manufacturer is. From the looks of the throat, it does not look shot out but not sure about the bore. Also, shooting without the hider would be another possibility.

As for loads, not tried anything lighter than 55gr yet and been waiting for those Hornady 55gr pills to get back in stock... So far, H335 and BLC-2 gave me the best...unfortunately, their best not close to MOA.

Lot's of great suggestions! Thanks!!!

[m134b]

It's pretty hard to make an AR NOT shoot... Exceptionally rare are the lemon barrels. After that, the barrel nut can be torqued TOO much, or not enough... Check for a bulged bore, that'll send projectiles into the next time zone. Also, pull your brake and check the pattern escaping gasses have left, if it's not even your crown is bad. You've checked your optics and mount, so that rules all those variables out.

I'd be VERY suprised if it's not one of the above!

Ken

[kamikaze1a]

It's pretty hard to make an AR NOT shoot... Exceptionally rare are the lemon barrels. After that, the barrel nut can be torqued TOO much, or not enough... Check for a bulged bore, that'll send projectiles into the next time zone. Also, pull your brake and check the pattern escaping gasses have left, if it's not even your crown is bad. You've checked your optics and mount, so that rules all those variables out.

I'd be VERY suprised if it's not one of the above!

Ken

Great tips. Short of a visible bulge, how would I determine that the bore is bulged?

Thanks!

[m134b]

You can usually see even a slight bulge by looking at a bright light through the bore. It won't "look" right..... Sometimes you can feel it when cleaning with a really tight patch being pulled through, there you'll feel a slight change in resistance at the bulge. A lead slug can definately tell you if you're careful.

There are other options, but I've no experience with them, like the Hawkeye borescope, air gage, etc. both are NOT cheap, the above will usually tell you though

Ken

[mdschappell]

My rifle started shooting all over the place, and I noticed that the barrel had gotten a little loose. It was tightened up and the groups tightened right back up to where they had been. 3" at 50 yards is pretty bad, and not at all where an AR should be shooting. Re-check that barrel before buying a new one.

[LT45]

Brand new out of the box AR-15.. took me a couple of years to find out that the barrel nut was never tightened at the factory.

Must have been the last one off the line on a Friday!

I went through 4 different optics thinking they were the problem.

Tightened the barrel nut.. now it splits hairs!

[kamikaze1a]

Question for all of you that had loose barrel nuts...could you tell it was loose visibly or only by turning the nut? I tried to move my barrel by hand and it did not appear to have any play laterally. If looseness can only be determined by torquing the nut, I will attempt to remove the forend as the previous owner used locktite on the forend nut...

[kamikaze1a]

Well, it looks like the "good news/bad news" adage is very applicable here...

I heated and removed the forend and found that the barrel nut was not "loose". It was snug but not tight, probably the low end of the torque range.

Using my YHM wrench, I backed the nut a bit and snugged it back down. With light tightening, the nut went back to the original position and more torque, it went past the original position but the gas tube did not align. I tourqued it more and one of the pins snapped off. So now, the nuts tighter than it was but the gas tube hole is out of alignment and no way to turn the nut in either direction.

So, ordered better wrench with five pins instead YHM's three and the new tool has provisions for torque wrench attaching. The YHM tool is less than a foot long so pretty sure I did not apply much more than 80 ft/lb...I guess I am stronger than I thought or the tool is weaker...

Question, I believe 30 ft/lb is the min and 80 the max, should I use shims if the holes don't align at 30 and 80 won't get it to the next hole?

Oh yeh, I confirmed that the rifling is 1-9 and found a thick (1/16") layer of very hard carbon on the crown of the barrel. It was hard enough that it would not come off with my thumb nail even after soaking in solvent overnight. I ended up very carefully scraping off the deposit with my knife being sure to not damaging the crown. Maybe that carbon contributed to the inaccuracy...

Edited July 5, 2010 by kamikaze1a

[warpspeed]

I'd guess the fouling at the crown had more to do with the accuracy issue than anything else.

As far as the torque, get to 30 then just enough more to line up. Making sure to use the appropriate grease of course.

[kamikaze1a]

I'd guess the fouling at the crown had more to do with the accuracy issue than anything else.

As far as the torque, get to 30 then just enough more to line up. Making sure to use the appropriate grease of course.

Thanks for that...as for tightening the barrel nut, problem was, cinching it down to about 30ft/lb indexed the hole just past aligned. And tightening to the next lineup required a lot more pressure, which broke the pin off the tool. I used to be a mechanic so I would dare say I could get pretty close to 30 by feel but getting to the next hole with less than 80ft/lb may be a problem... I think the original assembler probably found the same results so backed it off to align. If I'm not mistaken, that's a bad practice. I believe it is align by tightening? So back to my previous question, should I look into barrel shims?

[Loves2Shoot]

Make your own hole...

[dshooter3]

Don't worry about shimming the barrel just grind off the tab when you have the torque that you need.

[m134b]

You can tighten and loosen the thing a few times to get it to "line up". While others are correct that you can grind the offending tooth off without detrimental effect, it's still best to do things right. Apply either silver anti-sieze, or high temp bearing grease, and torque the thing til' it ALMOST lines up, back off, repeat, then tighten to where it needs to be. Little more work, but no grinding slivers and dust, looks better, and allows you to reuse the nut if you ever decide to swap barrels!

Ken

[Vlad]

I can tell you that the last set of YHM barrel nut instructions are rather bogus. They say to hand tighten as far as you can that use a wrench to align the next gas tube hole. That is a recipe for it to get loose after .. oh 100miles of rattle in a cargo container of an RV? Ask me how I know. I'd say you are on the correct path, tighten by hand, use a wrench to go to the next gas hole, and then the next one is your friend.

[kamikaze1a]

Thanks guys! Just received notification that the new nut and tool is in the mail. Regarding the nut indexing, unfortunately, this barrel nut is not like the original design so no tabs to grind off. This ff forend uses a nut with threads on the outside and holes running the length of the nut. Good idea though...

Thanks again and will use those torquing methods and hope I get a good indexing with the new nut.

[warpspeed]

Hopefully the new nut will work but cutting out the section necessary for the tube to line up is not unheard of, just not super clean.