Trouble shooting AR range day

[TraumaControl]

I am just starting out shooting as a serious hobby the past the last two months. I have a custom AR-15 that I bought from a family member gunsmith which has a EoTech VuDu 1-6x optic. I took it to the range today and tried to zero at 100 yards. Bore sighted at 25 then took first shot and hit left approx 5 MOA off. The scope adjusts 0.2 mrads per click so did the conversion and adjust 7 clicks. Second shot was in the red but a little high. I adjusted 0.2 mrad down then fired off a 5 shot group that I was kind of happy with. The next shot however was low and to the right, followed by high in the center, then high to the right. I figured it was just me and moved to the top right target and couldn't get a group at all. I then shot the top left, bottom left, and bottom right to see if I could pick up on something I was doing, but there was no consistent pattern. Set up a new target and it was all over the place and eventually missing completely. I am not home at the moment to check the scope mount rings but I suspect that may be the problem. Other then that maybe the barrel got too hot? or maybe i just need to stop sucking. Any advice?

 

[PinesAndProjectiles]

Stop sucking. I'm only kidding. Welcome to the Hide.

Can you give us some more details about the rifle? Caliber? Twist rate?

What kind of ammo? Factory or reloads?

Were you shooting off of a bipod?

Did you use a rear bag?

How long did it take you to fire all the rounds on the target?

 

[DrainTheSwamp]

What kind of groups have you gotten with other rifles?

That 5 shot group in the center looks good, something or someone got wonky after that.

 

[Namekagon]

This smells of optic mount or something loosening up as you went.

 

[TraumaControl]

The rifle is a custom AR15 built for me chambered in .223/ 5.56 and the spec sheet he gave me for the barrel is a Ballistic Advantage 16" barrel with 1:9 twist rate. Just shooting factory ammo (Federal American Eagle 55 grain FMJ .223). Shot off sand bag and little home made sand sock as a rear bag. Was at the range for a hour, and this target was 20 min. Rest of the time was trying to troubleshoot, which included 10 min cooling off then trying to get back on target at 50 yards without success.

Since im just starting out the only other rifles I have shot consistently are Savage Axis 2 bolt action in .308 and a Marlin 1895 SBL lever action .45-70. Both with okay groups.

 

[Spblademaker]

I’d start with some match ammo and a white background target. Then fundamentals like a madman. ?

 

[308pirate]

I’d start with some match ammo and a white background target. Then fundamentals like a madman. ?

+1 on match ammo.

American Eagle 223 is great training/blasting ammo, but it's 2 moa capable in the best of rifles.

 

[ShtrRdy]

Is the barrel floated?

 

[AMGtuned]

+1 on starting with ammo. I have a 1:8 BA barrel, and it eats up 55gr-77gr nicely. I did, however, spend quite a few rounds chasing a similar sounding problem once: I would get a great 2-4 shot group, then the fliers came. Then, some time later, another great group, then the fliers. Even with Black Hills match! WTF!?!? So, I had my barrel guy take a look at it with his scope. There was a tiny piece of metal, apparently a burr from when the gas port was drilled, that had laid over and sort of mushed itself into the rifling of the barrel. I was amazed, and stupefied at the same time. Bought a new Ballistic Advantage 16" 1:8 heavy stainless, had it Straightjacketed and never looked back. Good lesson learned, lots of ammo lost. Good luck. Buy more ammo.

 

[JimLee]

There's a multitude of things that can cause an AR to fire bad groups, check you scope mounting as you already plan, and then as others have said try some quality ammo. Hopefully you find your problem there. I personally would also check to make sure the barrel nut is not loose, I've seen those things back off a few times after taking out a new AR.

 

[TraumaControl]

Thanks for the replies. The scope mounting screws were pretty loose when I got home so I think that may have been my problem. Will start using match grade ammo as suggested. I just went out to get it zeroed quickly and ran into this problem and didn't want to repeat it next week. All this info though gives me a lot more to think through now as I get more involved in shooting. Much appreciated.

 

[Spblademaker]

I think Frank should include firearm prefire check as a fundamental. @Lowlight

 

[DownhillFromHere]

You might try 75-grain Hornady Steel Match to get a decent bullet at a decent price. This stuff is NOT garbage bulk ammo. My DMR-variant AR (18" stainless 1:8-twist barrel, 12-pound rifle with optic) would shoot consistent 1.0-1.25" 100-yard groups with it (but my Tikka bolt gun doesn't like it at all, nor does it seem to like ny 75-grain bullet). A 1:9" twist might be on the slow side for a 75 grain bullet, but worth a try.

 

[Trailgomer]

I use blue Loctite on all scope mount screws. Had the same type thing happen to me in the past.

 

[Eustice]

Sounds for sure like a combination of loose scope mount as well as “plinking” ammo. As said above, that American Eagle 55 grain stuff is 2 MOA ammo. Your results show that. Match grade stuff will change that variable. Check out Black Hills, Federal Gold Medal Match, Hornady, and (gasp) Magtech CBC 77 grain OTM for a cheaper match ammo option. I had good luck with Federal FC262 but it’s not being produced anymore. You may not be able to use the 77 grain stuff with a 1:9 twist but give it a try. There are plenty of other weights to look at. Federal Gold Medal Match 69 grain for example.

Good luck and please update the thread when you’ve tried some of the other stuff out. I love my SPR every time I shoot it.