AR accuracy issues

[Great-Kazoo]

Well my upper is in the mail being sent back as we speak, they said it had no problems and they tested it with 69 grain match ammo from Federal and Remington. Hopefully they included a target. They also said that 55 grain bullets are too light for a 1-9 twist barrel and I should shoot no less than 62 grain pills. Is this really true? It is a 16 inch barrel with a standard M4 hand guard. They didn't say how well it grouped. I should receive it Monday. It's about time though, they've had it since the beginning of January. I understand it has been cold, but this long to get it back? Springfield's turn around time has been 3 weeks tops for me, and I've sent stuff to them 3 times so far for various work to be done.

i have a few different brands of 55gr. swing by the house and i'll put a shooters ammo box together for you. my SBR and the spouses ar shoot 55gr great and both 1:9 .
i found the 55 and lighter ammo say 52gr's really shine in my 20" 1:12

[RARGUNS]

As stated above, the real formula concerns length not weight. But longer slugs are generally heavier which require a faster twist rate.

[YammyMonkey]

With the vertical stringing the first thing that came to mind was inconsistent pressure or the bipod. Have you tried shooting it off a soft rest with minimal pressure on the handguard? Pressure on a standerd forend will definitely change your POI.

Also could be bouncing around a little on a hard surface, but I'd expect to see less of a consistency in the shots with that.

[Byte Stryke]

With the vertical stringing the first thing that came to mind was inconsistent pressure or the bipod. Have you tried shooting it off a soft rest with minimal pressure on the handguard? Pressure on a standerd forend will definitely change your POI.

Also could be bouncing around a little on a hard surface, but I'd expect to see less of a consistency in the shots with that.

another reason I suggested a sled.

[jmg8550]

I have tried shooting groups resting the rifle fore end on a rest with similar results. I have not had a chance to test it with the ammo DPMS suggested yet. I will pick up some match grade ammo and see what happens.

[Irving]

You said you already did this, but here is an article you may find some what relevant.

http://www.theboxotruth.com/docs/bot51.htm

[ldmaster]

I once had an inaccurate rifle, along the lines of what is frustrating you.

Spent a lot of time on it.

Finally I realized that I was investing lots of time and stress in a 400 dollar problem. So I sold it, bought a new one - problem solved.

I used to be obsessive about getting my guns to shoot well for me, I still am, but realize that my time is worth something and some guns are just money pits.

If you've ever seen a barrel made, you probably know that a lot of it is done by hand, barrel blanks that have been bored and rifled are NOT 100 percent straight, they have to be straightened by an experienced barrel tuner. Then checked with a couple of instruments. Sometimes the tuner messes up.

Things you might want to check:

1. Your barrel crown. Even though you have a FH on it, it might have a few nicks in it (use a jewlers loupe and see if your lands and grooves are concentric and even. this is the most common problem with barrel inaccuracy, and nobody ever seems to check it.

2. Any torque placed on the barrel from the gas block interface with the handguards? Take the hanguards off to check. Think of it as a cheap free float!

3. Swap bolts with any other AR and see if you get the same results. We'd all like to think our bolts are true and mate 100 percent, but that's not always the case.

4. If you're handloading, drop velocity to 2700 at the muzzle. Sometimes the powder/primer/case/bullet combination is just wrong for YOUR gun. I was hugely frustrated with the accuracy of 40S&W ammo when it first came out (remember it's a neutered 10mm) and all the loadings were 180gr for practice. So I worked up a 155 gr load with alliant power pistol and small rifle primers. Worked very well and became a pet load of a local agency that used to reload their stuff for practice.


But personally, I'd just sell the thing if it isn't working well. DPMS PROBABLY swapped your barrel out, which may have done the trick. They don't waste a whole lot of time on this stuff, they just replace things until it works well and get it out.