I finished my first AR build this week, and hit the range with it today. The rifle ran 30 rounds without a hitch, cycles and functions flawlessly.....but it shoots 10-12" low at 100yds. Even with the elevation knob cranked all the way up, it still shoots a foot low. To add insult to injury, groups are 5-6 inches.

Parts include: Spike's Tactical upper and lower, 16" Red X carbine barrel (stainless, fluted, 1-9 twist), Troy low-profile gas block w/ Spike's gas tube, Hogue mid-length free-float tube. I tried two different scopes, both VX-III 3.5-10's, with the same results. Mount is a LaRue LT104, and it was tight.

I put the rifle together, so what did I screw up? Bad barrel, maybe?

Pretty hard to put it together wrong if you followed instructions.

The hitting low issue, can be resolved with offset burris ring inserts.

But I'd bet the barrel is a bit non concentric and causing the issue.
5-6 inch groups could come from cheap ball ammo, thats not unheard of.

But the low impact is either the mount, and would be hard to believe with a La Rue supposedly. Or the barrel.

Jeff

how cold is it where you are shooting, how old was the ammunition, who made the ammunition, and did you try any other ammunition to see if it was similar.

Interestingly we've shot down to about 10 degrees in matches, I've never seen an impact issue to speak of other than the expected due to MV loss.

Swap the Larue end for end,

Were all of the upper parts new, or a mix of new and used?

What was your torque on the barrel nut on the Hogue tube? Did you back it on and off, or just torque it down once?

What do you have on the muzzle?

we have no idea "what" ammo he is shooting or how cold it is. It would at least be nice to know if two different ammunition would hit in about the same place.

Here is a picture of the rifle:


More info to answer some of your questions:
- The rifle was built 100% from brand new parts, mostly from Brownells (barrel, handguard, gas tube, gas block, lower parts kit, stock kit). I got the upper and lower receivers from a gun shop. The charging handle and bolt carrier group came from a different shop. If it turns out to be a barrel issue, I'm hoping Brownells will accept a return.

- I just used a standard A2 flash hider, nothing fancy. It aligned properly without needing a crush washer, so I skipped the crush washer.

- The scope mount is a LaRue that I'd bought 5-6 years ago, directly from LaRue. It's been on 2 or 3 different AR's without issue, so I don't think it's a mount issue. Using two different scopes on the same day, with identical results, leads me to believe it's not an optics issue, either.

- I put the Hogue barrel nut on the way Hogue describes in their directions....finger tight lined up between two holes, so I tightened with their plastic tool to line up with the next available hole. I tightened it in one motion, no back and forth, and the gas tube slides in without issue. Once it was tight, I've never touched it or backed off.

- The ammo was my handloads (69gr SMK, Benchmark powder, Rem 7-1/2 primers, Rem cases). This particular handload consistently shoots under an inch in the previous AR's I've owned from Rock River. I didn't have another AR at the range yesterday to compare against and know for sure, but my gut tells me that the 6" groups are not an ammo problem. It certainly could be, though, so I'll bring some decent factory ammo along next time, just to see what's what.

- Temps were in the upper twenties/lower thirties. It was raining on the way out, and we were commenting that maybe we really didn't need to be out on the winter roads. We saw several bad accidents on our way to the range.

well the 1-9 should be OK with the 69MK's so that ain't it, and its not some chineese ardvarkian ammunition, two scopes leans against scope problem unless they were both hosed...

Nice looking build!

I'd look at the barrel nut, just one seating of the barrel nut may not have been enough to fully snug the barrel extension into the upper receiver extension. Generally, tightening it down, and loosening back up a few times (3-5) will get the barrel extension fully seated against the upper receiver. I would also get a torque wrench and get to the recommended 30-80 ft lbs.

It is possible that the upper reciever face on the extension is out "true" on the top and is forcing the barrel to point down a few degrees. But, it would be as likely as a barrel bored out of true with the bore, possible but not likely.

Can a plastic barrel nut wrench even get the nut tight enough without stripping?

Ddin't see this before my last post... thats a bad barrel IMHO.

Can't be much worse than the orignal rubber strap wrench ideas...

Brother Rost, respectfully, that post doesn't help him much without the "why" behind it.

Just for giggles turn your scope mount backwards and see what happens.

AH64, you don't always find out why. I love finding out why. But sometimes its not in the cards.

The first thing I"d do, besides flipping the scope mount, would be get a new barrel.

Pull old off, put new on. If problem goes away, its solved. Send old barrel back in with a note etc.... and hope to get your money back.

Sometimes finding out why is too expensive in time... vs just spending that in cash and solving it.

Dan,

I've got a barrel you can borrow to see if it's the barrel or something else.

Tracking...you labeled that as a "bad" barrel, IYHO.

Why do you think it's a bad barrel, what in that picture gives it away as bad, that some of us other readers may have missed?

Ddin't see this before my last post... thats a bad barrel IMHO. [/quote]

Sorry, missed the point which I"m apt to do ducking in and out of office during day and speed reading....

5-6 inch groups would be a good start. As to why. I've not seen an AR that would shoot worse than 2 inches at 100 ever. And that was with the cheapest model one sales barrel you could get.

And the fact its hitting a foot or more off, actually more at 100 since its a foot off with max scope adjustment.

I've seen barrels that were not snug, still shooting good groups, well under 5-6 inches.

I'm inclined to think there is something in there, and it might not only be the barrel but the chamber.

I also have barrels Dan can borrow, but I was hoping a local would offer first. Which has happened.

But I do have a new Shilen somewhere never fired... if Dan needs to try it.

I have, a DPMS SASS. six-seven inch groups @100yd. Same rifle would cloverleaf 77gr Gold Medal.

Dan, in comparison to the experts above I'm kind of a noob in the AR game, but there a few comments above that really caught my eye.

AH64's comment about how to snug a barrel nut. That's the first thing I would try.

Rosts comments about the barrel. Personally, I've never heard of a Red-x barrel, but considering the price, and the you choose a fluted model, I highly doubt they re-stress relived the barrel after fluting.

Ammo. I have a match .308 that shoots 12 MOA groups with 155gr NCC's but shoots 0.12 MOA groups with NBT's. Some guns just do not like certain ammo's, so you need to eliminate this variable as well.

As for my personal thoughts: I've had bad luck with Hogue products in the past (excluding their pistol grips). I'd get rid of their cheap gimicky barrel nut and replace it with a real one.

Next, I'd check the front of the upper receiver to insure it appears straight and true.

Here's an additional thought. If you can, withing spec, turn your barrel nut one more hole. If your groups go from being a foot low to a a foot to the right, you know you have a bent barrel, and someone owe's you a refund.

Did you bore sight it?

How did that go? Does the rifle shoot off of what bore sighting indicates?

Carnac I mean Jeff could be right, but I would shoot two or three factory loads in it save the targets, and then call RedX barrels or whoever they are.

I have, a DPMS SASS. six-seven inch groups @100yd. Same rifle would cloverleaf 77gr Gold Medal. [/quote]

My bad, I'd assume that folks are trying a couple of GOOD ammo choices before voicing concerns. Thats standard and not just for ARs.

I have hogue tubes on a couple of cheapy uppers... never had an issue with them in regards to performance or accuracy.

Just an FYI, and its literally a sample of 3 total at this point. Everyone I have, which is 2 and a buddy has which is 1, will shoot sub moa with the right load.

BTW a GOOD barrel will shoot just about anything good.

Its the cheap ones that we've had to dig for to find nirvana so to speak.

A friend had a Model one barrel, that was supposed to be 9 twist, and we checked it, was pretty dang close.

The ONLY thing it would shoot was 40 grain bullets of some kind, but they shot around MOA or so as I recall. His may have shot big groups with the rest. I just don't remember. I know it didn't shoot anythign otehr than 40s good though.

I've had several ARs. I'm not a total stranger to the platform, but I've never put one together from scratch before. Thank you guys for all of the suggestions. I will certainly look into most of them.

Trying different ammo is easy enough, and Cabela's has a bunch of .223 on sale this week. The bullet holes from the 69-grainers were perfectly round, so I don't think it's a twist issue, but it's no big deal to check. I'll get a couple boxes of different bullet weights to shoot.

I didn't bore sight the rifle; I don't own one. When I sold my last AR (Rock River ATH Carbine), I just removed my LaRue/Leupold setup and stuck it in the safe. I figured it'd be close enough to get me on paper, and I could go from there.

I'll remove the barrel nut and see what there is to see. Maybe I got it cross-threaded or something? I'll employ a different technique when retightening it. It took considerable force to get it tight enough to line up with the next available hole for the gas tube, so I doubt I'll be able to crank it to the next hole without breaking something.....namely my hands as they slip off that stupid plastic "wrench." I think it's as tight as its gonna get without involving a pipe wrench. I don't think it needs to be THAT tight, does it?

I bought two identical barrels, one for me and one for a friend. l could put the other barrel on this same upper receiver and see what happens. I've got an extra upper and hand guard, as well, to see if that doesn't change things. I've got parts to swap around, so I might be able to stumble across an obvious culprit in the process.

I don't understand the idea of turning the scope mount around, though. Perhaps the suggestion was in jest, and I missed it, but I'm not sure I could handle the Jeff O shooting stance the reversed cantilever would require.

Did you put anti-seize on the barrel nut?

No, just a little CLP grease.

That'll do, no grease and it can seize/gall. Gettin' it off is then a problem

Just swapped the barrel with the other one I had. I got the Hogue barrel nut off, wrapped it a couple of times with a shop towel and went at it with a set of Channel Locks. No damage, crossed threads or anything like that. Everything looked as it should.

I did notice that the crown on each barrel looked less than ideal, a little rough. That might help explain the poor accuracy.

$100 for a SS barrel on their website, you can get a BHW barrel for $260.00

I've seen factory RRA wilson tubes come with a crown that looked like it was done with a 5/16 drill bit...

Had a guy that was having a few issues, but not quite as bad as yours, smith cleaned it up and it was fine then.

An AR is one of the easiest rifles there are to bore sight. Just remove the upper and lay it on some bags. Remove the BCG. Look through the bore and see where it points. Adjust your scope until the scope is pointing at the same spot as the barrel. First shot X!


At least 50 ft lbs tight.



Sometimes scope mounts are not milled straight, sometimes the mount is improperly installed and doesn't bear flat on the upper. Swapping ends addresses both of these issues. You are naturally going to pay more attention to the process when you do this.
Since your problem was with elevation, I strongly suspect improper installation, especially after you said the mount worked on another rifle.

Having seen a lower milled with a trigger or hammer pin so off center, that you could see how crooked the hammer( now that I think of it, it had to be the hammer pin) was once in place and it was bad enough we sent it back...

I wouldn't bet against anything at this point.

BUT I'd bet that off target and horrible groups say barrel.

Off target and good groups could point to something in the upper not milled correctly... such that its not stressed so to speak, but simply not pointing where we expect them to.

Wilson Combat barrels still on sale, 1/9 is $165 and $10 to ship:

http://shopwilsoncombat.com/Wilson-...ist-Stainless/productinfo/TR-556RC16-19/

Are you certain the front part of your mount is firmly seated and tightened? I'd take it off and reinstall it before doing anything drastic.

http://www.brownells.com/.aspx/lid=11004/guntechdetail/how_to_build_an_ar-15_video

It has been a while since I reviewed the Brownell's videos but I am almost certain they suggest a nut torgue of about 38 foot pounds as a minimum? Don't have time right now to verify that.

Is there a way to get a nut adapter thing and actual foot pound torgue wrench on your set up? Working with machines all my life I am always looking for verified numbers no matter if it is temp, pressure or clearances or voltages. Just an objective number to work with as a start.

The barrel nut wrench comes with a recess for a torque wrench. The FM specs 30-80lb, IOW, if the gas tube hole lines up at 30, you're good.

Yep, the mount and scope were the first couple of things I checked.

Ignore the 5-6 inch groups, that's not the interesting problem here. The problem is why it's grouping LOW.

Group size is a function of the chamber/crown/load and bullet likes - why it's grouping consistently LOW is what's bugging Dan I suspect and I sincerely doubt swapping from what he's shooting to a top tier bullet/load is going to make it go from 5-6 and a foot low to 1-2 and dead on. It will help one of them and probably not the elevation IMO.

There has to be a mis alignment there to cause that with the ele maxed out on the scope.

Any chance the scope crapped the bed and while you've maxed the ele - its not actually moving?

If the other barrel you installed still shoots low you may need to square up the reciever. Brownells sells a tool for a power drill. I've seen some have the windage maxed out and still shoot wide. Squaring the reciever thread face cured it.

I just got back from the range, and here are the results....

The old receiver with the new barrel worked just fine. I was able to sight in at 100yds without issue and shot a 2" group. Nothing special, but it worked.

The old barrel on the new receiver had the same issues...a foot low and horrible accuracy.

I'll call Brownells in the morning and see if they'll let me return the bad barrel.

Thanks Dan, we appreciate the update.

Glad to know we could steer you in the right direction.

Sucks when that happens, but its good you figured it out!

First post got it right.

Good Job Jeff.

For an "educated, corner-office" type, you don't read too damn well.

My reading comprehension is just fine.

But since drawing the conclusion involved an attention span that could transverse 40 posts over a weeks time, it doesn't surprise me that you missed it.

Eh, I don't sweat these types of folks too much....

No big deal but generally with an AR if there is an issue like this one, its almost always going to be a bad tube with that bad of accuracy and that far off on impact..

Not always but mostly. At least in the "couple" of barrels I"ve dealt with over a "year or two"

Jeff

It was the UPPER genius.

the irony here is huge....

How do you figure?

Don't doubt him, he's shot mofos in the face. And can do pull-ups.

I know. that's why I worded my insult carefully....

no worries. he's having another meltdown and will be flushed again any time now...

I'll feel like I'm playin' cards with my brother's kids".

The end of the upper needs to be trued 90 to its centerline .

You know, the part the BARREL seats against.

NEVER said I've shot anybody. Fat MOFO's like you like to make up all manner of things though.

your brother's kids must tire of taking your money.

read again slowly.

Assuming that Dan's old barrel worked, it appears the problem is in the new receiver.

Old receiver + Old barrel = OK

Old receiver + New barrel = OK

New receiver + New barrel = No go

New receiver + Old barrel = No go

So, the variable I see is the new receiver.

4321, are you really this dense? Or is it just some joke I'm missing?

I did read it you silly fuggg, unlike you, I'm smart enough to interpret it. The axis of the threads aren't concentric with the END OF THE UPPER. That is why the barrel nut will snug but there is still enough vertical play in the barrel, where it seats against the upper, to cause the inacurracy.

Only a small portion of the barrel flange is in contact with end of the upper.

so why is the 'old barrel' BAD on both uppers?

and the 'old upper' fine with the new barrel?

He put a different barrel on the upper and the problem was solved. Nothing wrong with his upper. Read it again.

That's why it ain't the barrel genius.

Never underestimate your ability to overestimate your ability.

that is why it IS the barrel, retard...the 'new' barrel is a replacement brought in to troubleshoot.

the 'old' barrel is 'bad' on both uppers

Then why is the new barrel fine with the old (read not-effed-up) upper?

'old' upper is the one that shot low in the OP...

DaninAK nailed it.

Obviously well trained in differential diagnosis and logic, as am I.

yea. as are you. problem is, the "Assuming that Dan's old barrel worked". Dan's old barrel DID NOT work. it is the barrel in the OP

Maybe that clears it up?

For the non-tards, yes.

Who's on first????

old barrel is bad on both old and new uppers.

rost nailed in the first reply

Dan gets it.

[quote][I just got back from the range, and here are the results....

The old receiver with the new barrel worked just fine. I was able to sight in at 100yds without issue and shot a 2" group. Nothing special, but it worked.

The old barrel on the new receiver had the same issues...a foot low and horrible accuracy./quote]

What is so hard to understand here. The new barrel worked fine on the old receiver. The barrel is not the issue. As I posted earlier. You need to square the face of the new upper.

Read the entire post..please

The OP is CONFUSED AND WRONG, just like you.

I think there's obviously some misunderstanding about what Dan is calling his "old" and "new".

Since he came to the conclusion that the barrel was bad, I think it's pretty obvious from the context that the "old" barrel and receiver are the barrel and receiver from the original post in this thread (that wouldn't shoot). The "new" barrel and receiver are the parts he replaced on the AR that wouldn't shoot to try and figure out the problem.

Read it again like this....

Bless your heart.

Blue, you got dragged down into a basement and issued a "bless your heart." Don't you feel belittled? Lol.

Yea right.....

I wish I could've seen his face when he figured it out.

I am afraid you will be waiting a long time. Ain't gonna happen.

Didn't have to read it the new way. It's damned obvious on the first pass.

You'd think.

You might could but for elevated glucose.

I think I'll go get another swig of Evan Williams and try to read this thread again.

I am wondering how it turned out. Did Brownells do you right?

I also wonder what makes a barrel do that. I wonder if it was a screwed up install for the extension??? Or a bent barrel?

I'll call Brownells in the morning and see if they'll let me return the bad barrel.

Yes, Brownells did right by me. I called and asked them about returning the barrel, and they said no problem.

I ordered a stainless 16" White Oak barrel as a replacement. I got notification that it shipped yesterday, but hasn't arrived yet.

Glad to hear it; seems like Brownells is a class act. Hope things work out.

Very good read, this. I sure learned a lot.