Inaccurate AR-15

[cmb3366]

I am in need of help and ideas, first I'll offer some details on the rifle. The upper is a PSA premium with FN button rifled, chrome lined 1:7 barrel, LW contour, 16" with mid length gas. Standard handguards and A2 front sight post. Lower is Anderson with a Colt A2 buttstock kit, bushmaster lpk internals, Geissele GS2 trigger, and an accuwedge. The primary sight is a known-good Leupold VX-II 3-9x40 mounted in leupold rings on a riser. I have also shot the rifle with carry handle irons.

Now the story. I built this rifle originally because I was enamored with my M1 and wanted a service rifle that was a little easier on the wallet to shoot in volume. My though going in was that if I could get a modular rifle capable of holding honest 1.5" groups with match ammo and a clean barrel I would be happy, figure 2.5" with service ammo would be acceptable.

Long story short, I can't get the rifle to group worth a damn, not with irons, not with a scope, not from a sling, not from bags. I've struck out with reload employing 55gr, 60gr, 62gr, and 75gr bullets and all manner of powder charge. It shoots patterns with m193 in the realm of 4" groups at 100yds. Today I broke down and tried Federal Gold Medal Match 77gr. Started off with a five shot group at 100 with one 'flier'... The shot felt fine, so I thought a little bigger group was in order. In strings of 5 with time to cool between each, I fired a 15 round group. Surprise, when I lay it over the initial 5 round group the horizontal dispersion is identical.

I am at the end of my rope with this rifle and I've run out of ideas. The barrel nut is tight, the flashhider is tight, the barrel has been shot both meticulously clean and pig filthy with no noticeable preference (accuracy sucks either way), and I've put a little shy of 700 rounds down the pipe and I have not found a load that is accurate enough to make it interesting.

Does anyone out there have any ideas as to what may be going on? is there something I might be forgetting to try or overlooking? Are my standard just too high for a rifle with a LW barrel? I appreciate any and all constructive input.

 

[Thermactor]

You got me at PSA.


The barrel might simply be out of spec. Did you slug the bore?

 

[Jackal]

I'm guessing you are putting stress on the handguard. Pencil barrels benefit more from a free float handguard than any other profile. It doesnt take much stress to change your poi. Try firing with the magwell on the rest, not the handguard. Then you will know.

 

[cmb3366]

Good thought.

I'll slug it tomorrow after work and post the results. I will say I feel no loose spots with a snug fitting patch, and it is one of the smoother, easier cleaning factory barrels I have been around, though I attribute that the chrome.

Keep em coming.

 

[1911 guy]

Did you install the barrel yourself, or did the upper come complete from PSA?

Sometimes, but not always, accuracy begins to suffer when you approach maximum torque on the barrel nut. However, the problem isn't extremely common and most nuts align well short of maximum.

Tho other issue, mentioned by Jackal, is handguard stress. Lightweight barrels are sometimes very finicky, especially when slung up. When shooting from bags, place the front bag as close to the receiver as possible to minimize the leverage applied to the muzzle end.

 

[briansmithwins]

Barrel nut is tight, but is there any motion between the barrel and the upper receiver?

I've got a couple light contour midlength ARs and both shoot about 1.5MOA groups when rested on the handguards.

BSW

 

[wally]

My bet is that Jackal has nailed it.

I've got an M1A that is useless with a sling as any change in tension moves the shot.

Either change the barrel (for one that is stiffer) or try a free float tube. For economy builds, I really like the UTG Super Slim Free Float tubes, ~$85 if you shop around.

 

[joem1945]

I had a 24" heavy SS barrel 1/8 twist. I fooled with it for 2 years trying to get it to group. Tried diff powers, primers and a bunch of bullets. Recrowned but no joy. Got Pi$$ed of and took a rotary file in a cordless drill to the muzzel. Felt it grab on the right side of the barrel and figured it was toast. Surprise groups under 1" with 77 gr Black Hill match ammo. Must have been a booger in the barrel.

 

[readyeddy]

I think the OP has made a good faith effort to see if the upper can perform properly. According to the PSA website, they will process returns if they manufacture a firearm that does not function properly.

4" with M193 may be within spec, but I would also be dissapointed and would attempt to negotiate a return if nothing works.

 

[NWcityguy2]

While I'm not doubting your efforts, I think the rifle is grouping within what is acceptable for a 16", lightweight, chrome lined barrel. It is at the lower end of acceptable, but acceptable nonetheless. PSA doesn't make any accuracy claims, nor is there any reason to think it is PSA's responsibility to give a refund or return.

Now I'm not going to lie, both my PSA Premium and my PSA Freedom shoot tighter groups than that, they are at or slightly below the 1.5" range. But if either of them was shooting groups like yours is, well, that's life. It's a service grade barrel, and while I sight mine in using a completely supported rest, they aren't meant to be shot exclusively in that position.

I'd recommend that you swap out the barrel, get a low profile gas block and free float it, if the primary purpose for the gun is to be shot from a bench.

 

[Lord Teapot]

that's nuts for 100 yards

even my trash bushmaster carbon 16in can do 2 inches

try putting it in a vice and seeing if it shoots tight, then you'll know if its the barrel or your method of holding it affecting the barrel on each shot.

 

[carbine85]

I wouldn't expect much from a CL LW barrel. You don't have much working in your favor. If you change the barrel I would go with a mid length, 1:8, CM or SS. You can get fluted barrels that don't weigh much more than what you have.
Have you tried the scope on anything else?
What type of muzzle device are you using?
Check the crown.

 

[Stephen1956]

My son has the same problem with his M&P-15 and Yankee Hill rifles I have a $500.00 AR with a 1:8 twist and can get about inch and half groups at that range. I use reloads and 69 grain is the heaviest bullet I use plus I shake a little and I don't use anything but a home made bag rest or just grab the front of the magwell and shoot.

 

[cmb3366]

Going to hold off on slugging, I've done the process on my 357's, but on further consideration the idea off driving a piece of lead with a dowel small enough for a .224 bore does not give me warm fuzzies.

The idea of pressure from the rest affecting the barrel is a good one. Up to this point I have only benched the gun using a bunny ear rear bag and a pedestal front providing support at the hand guard. Seems if I can get a group out of it without forend support, the answer would be a free-float tube. I will shoot it this weekend with support on the magwell and buttstock only and report back, May even fire a group without handguards attached.

The muzzle device is an A2 flashhider, no obvious signs of nicks at the crown.

The scope came off my muzzle loader, upon which it delivered superb accuracy. I initially tried a new to me Leatherwood ART 600 which I fired with crummy results. I switched to the Leupold to eliminate the scope as a variable.

I did not expect target rifle accuracy from this setup going in, just good enough to hit what I shoot at out to a reasonable stretch from field conditions. As it sits, beyond 100yd it is useless, at 300 this rifle cannot even hold the black, and I get no enjoyment shooting it for noise value only.

Essentially the purpose of this thread is to get some input on whether I am reasonable to expect better from the current setup and barrel, and assess whether options like a free-float tube could really turn it around.

If I strike out, I'll pull the barrel and install something of the heavier contoured unlined variety, which I'm now wishing I'd gone with from the start.

 

[cmb3366]

And just in case anybody is wondering why I would stick a big scope on a light carbine, the scope is just a band aid I've employed while attempting to first find a load, and now, chase down some obvious gremlins.

Just to clarify, here are some pictures of the rifle in question, starting with the barrel


The rifle as it currently sits


What my shooting setup thus far looks like

 

[cmb3366]

Also, the barrel is not a true LW contour. It's what PSA calls a modified A2, SKU28087 shown here http://palmettostatearmory.com/inde...ped-upper-without-bcg-or-charging-handle.html

 

[NWcityguy2]

Yeah, PSA's LW contour is different than most. It is approx .625 under the handguards, .750 for the gas block and then back to .625 for everything past that. It's not bad or good compared to a straight .625 barrel, just different. Their pencil barrel is more akin to what most companies call LW profile.

 

[TIMC]

Get rid of that big honker of a front sight and put on a low profile gas block. I don't see how you can possibly see good through it the way the scope is mounted.

 

[kwg020]

If you have the time, I would lap the barrel with some JB Bore Bright and make sure there is no large amount of copper in the barrel. I like Brasso for lapping bores while using a plastic bristle brush. I also like the idea of getting any pressure off of the hand guard while shooting from the bench. Good luck.
kwg

 

[Inebriated]

I'd free float it and go from there.

 

[wally]

Get rid of that big honker of a front sight and put on a low profile gas block. I don't see how you can possibly see good through it the way the scope is mounted.

Not an issue, at magnifications above ~2X the front sight tower is so out of focus all it does is make the image imperceptibly dimmer.

Only if the scope goes down to 1-1.5X do you need to consider a flip up front sight if seeing it through the scope really bothers you.

If he free floats it, a low profile gas block will offer the option using a longer free-float tube, at the added cost of needing to buy a flip up front sight if he wants BUIS, although the 45 degree offset sights then become an option. But you can free-float with the original sight tower/gas block using a 7" (carbine) tube.

 

[HB]

Hate to be that guy but it will be cheaper to buy a new barrel or upper than deal with what you have. I don't know much about ARs but we live in an era of extremely accurate rifles for the money. There's a reason that gunsmiths are a dying breed. It is cheaper to replace the gun than to make it work right.


Unless this gun has sentimental value (not sure how an AR could) I would send it down the line. If you've fired 700 rounds and have made no progress another 700 isn't going to help.

If it were your grandfathers mauser based sporter id wholeheartedly agree to keep trying but on an AR I'd get a new barrel or new upper configuration. You've already put the cost of that in time and ammo through the gun.


HB

 

[wally]

Hate to be that guy but it will be cheaper to buy a new barrel or upper than deal with what you have. I don't know much about ARs but ...

Not until he's tried Jackal's suggestion of shooting without anything touching the hand guard (barrel) to see if a free float tube could be the solution. Costs only a few rounds and some time to do the test.

If that fails I'd pull the flash hider, check the crown and try it without the flash hider in case its causing instability (very rare as far as I know). It that fails then its time to replace the barrel or live with being in the lower end of mil-spec acceptable accuracy range.

 

[TIMC]

Not an issue, at magnifications above ~2X the front sight tower is so out of focus all it does is make the image imperceptibly dimmer.

Only if the scope goes down to 1-1.5X do you need to consider a flip up front sight if seeing it through the scope really bothers you.

I agree with that for the most part but the front sight post is higher than the scope which you do not want above centerline; it is probably causing some parallax issues. Even though it is not seen by the eye because it is blurred out it still blocks the entire centerline of the scope. I also think it would be pretty hard to get a good cheek weld on the stock and center your eye in the scope.
My first corrective action before busting out on a new barrel would be taller riser.

 

[cmb3366]

Getting a cheek weld is not a issue, the scope is in a comfortable and intuitive location. The target is not obscured by the front sight post. As I said before, the rifle as it sits right now is not what I had in mind when I built it. My plan was to shoot it with irons to build a skill I grew to enjoy shooting my M1. That said, off the bat I was having a hell of a time hitting anything, so I scoped it for what I thought would just be a little extended load development. What the scope showed me was that the rifle has some issues, not the sighting system or ammo.

I will shoot it this week avoiding contact with the barrel as discussed and post the data. A float tube would be an inexpensive fix if the groups tighten dramatically.