What would make my AR do this?

[Bat Rastard]

I tried a load today. I really had no hope for it. Many things were just not supposed to work:
90gr bullets with a 7.7twist isn't supposed to work.
I thought I would see pressure before I got velocity, I didn't. I averaged 2630fps with nice round primers.
It far exceeded my expectations on several levels.
I tried 2 5shot groups. Both were a cluster of 4, and a flier.
How do I shake the flier?

 

[DShortt]

Shoot a 10 shot group on 3 different days before you get too excited. Next time might well be a bust.

 

[Bat Rastard]

I hope to take another run at it tomorrow.
The wind was howling today. Maybe it was blowing them in.

 

[Jeff Porter]

I hope they work for you.
But … Look closely at the bullet holes. IF … you were square to the target at the firing line … the beginning of some yaw is seen with the black smudge not being uniform around the hole. Stretch it’s legs out further than 100 and see if they are stable out there too.

 

[Andy Legg]

Which 90 Grain Bullet are you shooting? I have thought about trying some 90's out of a 1/7 WOA at higher elevations than sea level (higher than Texas Gulf Coast=Home).

 

[dellet]

What shot number was the flyer?

Not uncommon to have first or last round in the magazine chamber differently. More or less force can cause the shoulder to set back differently, bullet to shift in the neck, velocity anomaly.

May just be that if you shot a 30 round group you would have five down there.

 

[Andy Legg]

Typically, 90 grain 5.56/.223 bullets are required to be loaded longer than Magazine Length and are most likely being single fed.

Either way, I would recommend single feeding while attempting to identify the cause of the fliers.

What shot number was the flyer?

Not uncommon to have first or last round in the magazine chamber differently. More or less force can cause the shoulder to set back differently, bullet to shift in the neck, velocity anomaly.

May just be that if you shot a 30 round group you would have five down there.

 

[karrarararararar]

1/7 will stabilize 90's. We also havent seen any mention of what cartridge OP is shooting. If 223, then loading 90's at mag length is a no-no and can be downright dangerous.

 

[jelenko]

How is the rifle being 'held'? E.g., off a bipod, off a bench?
What types of groups do you get with your other favorite loads?

 

[Bat Rastard]

90gr SMKs.
At 2.410, they are definitely being single fed.
I was using a bag rider on a pretty good rest.
On the top group, the fier was early on.
On the bottom group, I am not sure when it was. With it hitting in the line I didn't see it and assumed it was in with the others.

As to other loads performance, I am struggling to find consistency with that rifle. It will shine today, and lay down tomorrow.

 

[Bat Rastard]

I hope they work for you.
But … Look closely at the bullet holes. IF … you were square to the target at the firing line … the beginning of some yaw is seen with the black smudge not being uniform around the hole. Stretch it’s legs out further than 100 and see if they are stable out there too.

Would they get better or worse with distance? Is that what they call "going to sleep" ?

 

[Fast14riot]

B

Would they get better or worse with distance? Is that what they call "going to sleep" ?

Bullet yaw and precession are reduced as flight time increases. Think of a spinning top, starts a little wobbly then smooths out.

 

[Jeff Porter]

Would they get better or worse with distance? Is that what they call "going to sleep" ?

I have never observed a load that grouped better at distance than at short line by "going to sleep". I have had small sample size groups that suggest that is possible but in larger samples it evens out to a load that groups at 600 or 1000 will group well at 100 or 200. But, something that groups well at 100 may not group at longer ranges. I have never had a load that always shot poorly at 100 that always shot well at longer ranges once several groups were added to the data.

Alexanders spinning top analogy has another end to it as well. When it starts to slow down it wobbles more. I think the physicists call it precession where the yaw spirals around a point. I have observed this in a spotting scope where a friend had a load of 52 gr bullets that hammered little groups at 100 and 200 yards. It was running very slow and when we got to 300 yards, you could see the trace arcing nicely out to about 240 yards then start corkscrewing into the target in a very random unpredictable pattern.

I am running 90VLD at 2800+ fps in a 1:7.

At the 2630 fps velocity you have stated in a 1:7.7, I would be pleasantly surprised if it was a consistent tight grouping load at distance in larger groups size (10-20 shot groups).

 

[Coyotefurharvester]

Being marginally stable at 2650, stability isn't improving as velocity decreases(travels down range) because the projectile isn't spinning fast enough. The bullet loses 4 % of it's stability factor by the time velocity drops to 2000 fps.

 

[Bat Rastard]

I got out again today.
I tried 10 of the same, and 10 with a different powder that I thought would give me similar velocities.

They both shot like crap, and it was a much nicer day weather wise.

The pattern on top is Varget, the bottom is Leverevolution.

This experiment is over.

 

[jscore]

Looks to me like the old bolt catch release flyer. Shoot the same load again, but this time start with a closed bolt and rack it manually. Sometimes it works, sometimes it doesn’t. Been banging my head against a wall for years with that one lol.

 

[jds holler]

I've got the same going on with mine. This is pretty typical for me. And it's not always the first shot. So far, I've been reloading skanky old brass of questionable lineage, and I'm beginning to think that it's simply the percentage of bad ones showing up.

The factory ammo I've started using is more consistent, but the groups are more like 2-3 MOA.

If I could get the fliers under control with my reloads, I'd be pretty happy with what I've got. I'm a beginner with these little rifles, and appreciate any advice such as "jscore" above. jd

 

[jelenko]

I've got the same going on with mine. This is pretty typical for me. And it's not always the first shot. So far, I've been reloading skanky old brass of questionable lineage, and I'm beginning to think that it's simply the percentage of bad ones showing up.

The factory ammo I've started using is more consistent, but the groups are more like 2-3 MOA.

If I could get the fliers under control with my reloads, I'd be pretty happy with what I've got. I'm a beginner with these little rifles, and appreciate any advice such as "jscore" above. jd

View attachment 1543418

That looks like just under a MOA [assuming the target is at 100 yards].

Have you tried varying the powder charge?
How confident are you that the flyer isn't you?
What barrel is on your AR?

 

[Coyotefurharvester]

I would make sure you don't have bullets changing seating position when loading(doesn't cost components/money to check). Or bullet jacket damage from ramps or magazines(could be a left or right side only problem).

 

[Bat Rastard]

I would make sure you don't have bullets changing seating position when loading(doesn't cost components/money to check).

With more neck tension? Or a crimp die