Someone please tell me how this is even possible.

[357Max]

Gun is an AR in 6 ARC 22" 7 twist.
Bullets are PVA 100gr Seneca's suppose to have 7T min to stabilize, but I suspect it also needs 2850+ in addition to the twist rate.
Range is 100y.

First picture is 5 rounds, 1st is in the center of the target and was single loaded. The next 4 to the right are mag fed. Load length 2.370, speed 2733.

They're obviously unstable. How can something so unstable group so tight??? Makes no sense.

I figured this was some freak occurrence & yet it did it again.
Next range trip I loaded a little longer and hotter. 2.410 x 3 in Hornady brass over magneto @ 2770. With the magneto on 1 hole was round and 2 were triangular, group was Yuge.

Then I tried a repeat of the previous which was from Lapua Brass that has +.002 neck diameter. This at the same new load as the previous 3, this time no Magneto. Target below right is 3 rounds. I don't know if 1 was stable and passed through the other hole or if 2 triangles somehow lined up, but its definitely 3 shots.
Left hand groups are Berger 109's @ 2730

I've only shot 18 of these total & the 2 groups pictured (5 rd & 3rd both from the tight neck Lapua brass) are the only groups shot without the magneto.

I just don't understand how something this unstable can possibly group this tight.

I've had unstable loads with 85.5 Berger's in 224 Valk & they did exactly what I'd expect, shotgun groups in the 4"- 6" range.

Ideas anyone? Theories/Conspiracy theories, I don't care.

Talk to me Goose!

 

[357Max]

Seriously I'd like to know how the hell tumbling bullets can hold under moa groups.

Hard to believe no one has said these will go to sleep in another couple hundred yards. Come on man, take the bait!

I'd like to here hi def audio of these things approaching the target. Must sound wicked tumbling @ 2700+

 

[Sigma]

Seriously I'd like to know how the hell tumbling bullets can hold under moa groups

I would have thought the same thing until Bryan Litz posted this a few weeks ago regarding his testing on group divergence. I would have never believed it either….

 

[McCrazy]

My guess would be that since you are at the minimum twist rate and a bit slow on velocity, your projos are unstable but not tumbling.

This is making them yaw and impact at angles but they aren't outright flipping all over the place
and deflecting randomly which would result in the massive groups you expect.

 

[btuse]

Seriously I'd like to know how the hell tumbling bullets can hold under moa groups.

Hard to believe no one has said these will go to sleep in another couple hundred yards. Come on man, take the bait!

I'd like to here hi def audio of these things approaching the target. Must sound wicked tumbling @ 2700+

maybe reach out to Josh from PVA. He's a member of the hide. (Jasent). I had similar issues with the 245's and 212's and remember him telling me it was totally possible running through my 1:8 twist OEM while waiting on 1:7
I continued with the 1:7 tube, but still experienced a few sidewinders, which I attributed to inadequate velocity or just not finding that perfect combo. so I shelved that project to rest my brain and do more shooting. I will certainly revisit, as his mono's are very impressive ballistic-wise.

 

[357Max]

maybe reach out to Josh from PVA. He's a member of the hide. (Jasent). I had similar issues with the 245's and 212's and remember him telling me it was totally possible running through my 1:8 twist OEM while waiting on 1:7
I continued with the 1:7 tube, but still experienced a few sidewinders, which I attributed to inadequate velocity or just not finding that perfect combo. so I shelved that project to rest my brain and do more shooting. I will certainly revisit, as his mono's are very impressive ballistic-wise.

Your sidewinders probably fell way outside the group correct?.

I just have a hard time wrapping my head around how tight they shot while so unstable. Makes no sense at all.

The 25 cal 120 Seneca’s shoot lights out from a 7.5T Creedmoor, but there also running 3000fps.

 

[btuse]

Your sidewinders probably fell way outside the group correct?.

I just have a hard time wrapping my head around how tight they shot while so unstable. Makes no sense at all.

The 25 cal 120 Seneca’s shoot lights out from a 7.5T Creedmoor, but there also running 3000fps.

Yes. I had several tite groups, and then a long jagged rip 4-5' away on one string. The RO who knows my ability(but not mono's), insisted it was a ricochet from another bay and started freaking out. He too could/would not wrap his head around it.

 

[b6graham]

the 95 Senecas might be better

@bohem

 

[357Max]

the 95 Senecas might be better

@bohem

Agreed! Might even get drive band to touch at windowed mag length 2.385. Lower & upper are notched.

 

[bax]

Seems to me I read about different ways or aspects that a bullet could follow as it went down range. Perfect is when the bullet is spinning around the long axis of the bullet and that log axis exactly matches the computed ballistic curve - minimum drag, easy-to-compute flight path.

When there is a wind, the bullets tend to yaw, I think they yaw "into the wind"?

There is a case where the nose of the bullet is sweeping a circle. Think of a cone where the point of the cone is the center of momentum of the bullet and the big end of the cone points forward. The bullet is spinning on its long axis but the long axis is sweeping a circle. In the perfect case, the circle radius is zero - just straight ahead. In most real cases the bullet nose is slightly off the theoretical long axis so you get this kind of cone. I'm thinking I read about this in one of Brian Litz' books. Anyone else remember reading this or studying it?

The OP's bullets could be behaving like that - where they are yawing to a substantial degree.

I agree with the comments that if the bullet is flying weird, the drag for such dramatic yaw should be higher so they should drop more. Unless ... since the bullets are supersonic the simple intuitive concept of drag doesn't apply in the same way.

 

[Nosteponsnek]

I know this might be of much help but I remember talking to a old bullseye shooter and he was saying something about the 32 S&W wadcutters would tumble but were super accurate at 50 yds but that was with a pistol though

 

[Raffy]

Are you certain your barrels twist rate is accurate? In this case I would check it and see. Its probably not a bad idea to check all of them since it takes no extra time while cleaning anyways. I have heard recently of someone with a barrel marked and sold as x, but turns out it was y, and that explained all the problems he was having with load dev.