UPDATED Can you over stabilize a bullet?

[Gunnut26]

Testing a load today and getting some tumbling bullets, shooting a 104 grain 6mm at about 3130fps out of a 7.5 twist, any ideas or suggestions appreciated

 

[Idaho-Lefty]

Short answer,.. YES you can !
That's way too Fast for, a 1-7.5 Twist, 6 MM using over 100 grain bullets. IMO.
My best Accuracy using, 103 ELD-X's and 107 SMK's, in my 6 XC, 1-7.5 TW, comes at, just under, 2,950 FPS
5 shot groups are Sub 1/2 MOA with, the 103's and in the 2's and 3's with, the 107's

 

[alf]

Here's a 105 in a 7.25 twist with no issues:

 

[SKWERLZ]

Testing a load today and getting some tumbling bullets, shooting a 104 grain 6mm at about 3130fps out of a 7.5 twist, any ideas or suggestions appreciated View attachment 1445733

Not positive about over stabilization but you certainly can have the bullet fail because of excessive forces from spinning it fast.

Sometimes they unbalance and tumble, sometimes they disintegrate.

I’d also check muzzle condition and any brakes or suppressors on it.

I’ve had bullets that should be just fine with acceptable speed and twist tumble or go poof with some lots and not others, Hornandy 6.5 147 comes to mind.

 

[Gunnut26]

Not positive about over stabilization but you certainly can have the bullet fail because of excessive forces from spinning it fast.

Sometimes they unbalance and tumble, sometimes they disintegrate.

I’d also check muzzle condition and any brakes or suppressors on it.

I’ve had bullets that should be just fine with acceptable speed and twist tumble or go poof with some lots and not others, Hornandy 6.5 147 comes to mind.

I dont shoot brakes or suppressors and crown is in great shape its a newer build, these bullets just might not the faster rotation

 

[Gunnut26]

Here's a 105 in a 7.25 twist with no issues:

Alf which 105 are you shooting

 

[alf]

Alf which 105 are you shooting

Those were Hybrids, but I also worked with 110 Sierras, 108, ELD's, and regular 105 HVLD Bergers.

 

[HTSmith]

Has it shot other bullets without issue? If so that points to the bullets. Maybe too thin jackets?
If not--
Is it truly a 7.5 twist? Could be understabilized.
Is there a barrel or chambering defect?
Got a borescope?

There is an issue for sure and I don't think it's overspin, lots of folks shooting that class of bullet in the same twist at the same or faster velocity.

Just some thoughts

 

[Ranger188]

You have another issue going on there.
Thats not fast enough to "over" spin that bullet with that twist.
That's right at 300,000 rpms. That's not your problem.

 

[Gunnut26]

Has it shot other bullets without issue? If so that points to the bullets. Maybe too thin jackets?
If not--
Is it truly a 7.5 twist? Could be understabilized.
Is there a barrel or chambering defect?
Got a borescope?

There is an issue for sure and I don't think it's overspin, lots of folks shooting that class of bullet in the same twist at the same or faster velocity.

Just some thoughts

I have checked the twist its a 7.5. I first was shooting 108 Hottenstein and had no trouble. I switched to the 104 and hadn’t shot it much on paper. But it done this twice in a row. Im gonna load more of the 108s this week see if it does it with them.

 

[Gunnut26]

You have another issue going on there.
Thats not fast enough to "over" spin that bullet with that twist.
That's right at 300,000 rpms. That's not your problem.

I will try some different bullets this week see what happens.

 

[SKWERLZ]

I will try some different bullets this week see what happens.

Yea, I personally feel it’s a bullet issue though you are pretty up there in spin rpm (300k+ rpm) that can give cup/core bullets issues.

 

[topclass2017]

in my experience, some bullets (sierra, berger) are more tolerant of high rpm (>300K), while others (hornady) are not. I've had overspun bullets keyhole like the OP's. slowed them down and "most" of the problem went away with only an occasional keyhole. Solved the problem by changing bullets.

 

[Ranger188]

Try some Bergers or Sierras and see if the problem goes away.
What caliber are you shooting?
Who's 104g bullets are tumbling?

 

[swd]

Back the speed down about 200fps and see if it still does it. Probably the core coming apart.

 

[Bulletman]

You can spin bullets faster than is needed for good accuracy and stabilization, more than sufficient stabilization may not be detrimental but is not needed. What can occur and what appears that your setup is doing is that between the necessary bullet damage from the rifling and the high RPM the bullet jacket cannot sustain the forces and spins apart. Usually a grey puff is seen downrange and no bullet impact. You have a tumbling projectile that is sideways thru the paper, it appears that the bullet core went thru the paper with no jacket material involved assuming a pointed match bullet was being used. It appears from the limited data presented that something if this nature occurred

 

[Gunnut26]

You can spin bullets faster than is needed for good accuracy and stabilization, more than sufficient stabilization may not be detrimental but is not needed. What can occur and what appears that your setup is doing is that between the necessary bullet damage from the rifling and the high RPM the bullet jacket cannot sustain the forces and spins apart. Usually a grey puff is seen downrange and no bullet impact. You have a tumbling projectile that is sideways thru the paper, it appears that the bullet core went thru the paper with no jacket material involved assuming a pointed match bullet was being used. It appears from the limited data presented that something if this nature occurred

Thank you

 

[243winxb]

Clean the barrel well right in front of the cnamber. Any damage to the bullets jacket may cause this.
Undersize bullets is another.
Heat build up in rough bore may turn the lead core to liquid. More so in 28 or 30" barrels.
https://forum.accurateshooter.com/threads/berger-bullet-failure-test.2481280/

 

[wkdickinson]

I had a 308 Win, with a 1:8.5 twist Obermeyer 5R barrel that would not shoot Sierra 155gr Palma bullets. It shot 168's and above great. I talked to Sierra about it and they had no idea why. Only thing I could attribute it to was too fast of a twist.

 

[xswanted]

I’ve shot the 95 TMK from a 7 twist 6x47 at 3165. It shot very well out to 1000 yards. Zero bullet issues.

I’m guessing you had a jacket failure either due to over spinning or a bad couple of bullets.

Try some different combos and see what you get.