I'm getting a .260 Rem with a 1:8 twist. What is the lightest bullet I can shoot from it with good to optimum performance?

optimum I think will be 139/140 gr.
sierra or nosler bullets in the 120 gr shoot good in my 6.5 1:9 twist

What will happen if I shoot a 120 gr. bullet in a 1:8 twist?

The only "potential" problem is a lack of accuracy or bullet stability and keyholing.
Stability is also velocity dependant. The faster you push them the better they stabilize is the accepted norm.
I have a 6.5x55 Swede that I shoot modern loads in and it is a 1 in 8.5 twist.
It shoots 140 grain Matchkings at 2700 and 120's at 2900 and 100 grain at 3100 very well.
The fact is you can get keyboard advice out the wazoo but you don't know what YOUR rifle will like until you load for it and find its sweet spot.

Thanks. That's what I wanted to know.

Lightest 6.5mm Bullet ?

The lightest 6.5mm bullet commercially available is possibly the RWS 93 gr bullet
Hornady makes a 95 gr bullet, Norma 100 gr and Barnes a 110 gr bullet as lightest offering.

The issue of stability for a determined twist is not how light you can go but how heavy ( long) you can go given your chosen twist rate.

A 1:8 twist barrel will adequately stabilize the lightest bullets in 6.5 in fact the 93 gr RWS was designed specifically for their 6.5x68 which typically had a 1:250mm barrel and even 1:280mm barrels.

quote:

Originally posted by quarterbore:
What will happen if I shoot a 120 gr. bullet in a 1:8 twist?

Shoot any bullet you can find. Hard to over stabilize a bullet.

OK, here is what I have actually done; I have a Ruger Precision Rifle, 6.5 Creedmoor, one in eight inch twist rate. I shoot 140s and 120s in it with each trip tp the range; NO difference in accuracy. Both shoot exactly the same groups, always sub MOA and usually around .5 MOA.
As stated, overstabiliztion might be a thing, for some applications but I have never experienced it.

quote:

Originally posted by dpcd:
[ . . . ]
As stated, overstabiliztion might be a thing, for some applications but I have never experienced it.

A quick question about over-stabilization because the term "over-stabilization" sounds somewhat ominous.

Other than a bullet disintegrating when a very short/light bullet is pushed so fast it exceeds the rotational speed it was designed to withstand, what problems would over-stabilization cause?

How would one recognize over-stabilization if one saw it (other than a puff of grey)? AFAIK, I've never experienced it either.

Am I right that accuracy might suffer?

My thought is that loss of accuracy would be less a problem than under-stabilization (I've had bullets keyhole from under-stabilization).

quote:

Originally posted by ALF:
Lightest 6.5mm Bullet ?

The lightest 6.5mm bullet commercially available is possibly the RWS 93 gr bullet
Hornady makes a 95 gr bullet, Norma 100 gr and Barnes a 110 gr bullet as lightest offering.

The issue of stability for a determined twist is not how light you can go but how heavy ( long) you can go given your chosen twist rate.

A 1:8 twist barrel will adequately stabilize the lightest bullets in 6.5 in fact the 93 gr RWS was designed specifically for their 6.5x68 which typically had a 1:250mm barrel and even 1:280mm barrels.

Sierra makes an 85.

https://www.midwayusa.com/prod...low-point-box-of-100

BL: yes, accuracy is the only downside, Look at bench rest barrels; they are not super fast twists. A good example is the 7 inch twist of the M16A2; that number was derived from the twist rate that would stabilize the heavy tracer bullet at minus 40 degrees F. And later for the heavy penetrator core type 5.56 bullets. But It is not optimum for most 22 caliber bullets. And that is what they long range shooters use for the long 80 grainers. BUT, that is not what you want for bench rest shooting. Why? Because although the fast twist certainly will stabilize the light bullets, it also accentuates any imperfection in the projectile due to the rotational inertia on the bullet; since no bullet is perfect, you want to minimize that as much as possible. Hence the different barrel twists made today.
Another area where there are no fast rules; shoot it and see is the only true way.

So, what I gather is that with lighter, .223, bullets if they are spun out of the barrel to fast they could come apart due to the centrifugal force. But with the larger, .264 bullets, that is not likely to happen because the weight to length ratio is smaller than that of the smaller calibers. And that I will be good go go to shoot any 6.5 caliber bullet that I want to through my 1:8" twist barrel without fear of problems. Is that right?

That isn't going to happen in a 6.5. They are tougher by design, whilst some of the .223s are very frangible.

dpcd and quarter bore: Thanks. I just keep learning.

Well you are in luck because I am good at making up answers.

Actually when Lampel Fuerth of RWS designed the 6.5x68 circa 1940 they ran into the problem of light jacket bullets coming apart in flight with tight twist rates. Hence their decision to forgo tight twist barrels for the 1:250mm twist rate.
( 1: 9.84 inch) thus limiting the 6.5x68 in terms of bullet choice.

I have a 260 with 1 in 8 twist. I am using 100 grain Nosler Balistic Tip Hunting with no issues. Initial load I got just under an inch so I didn't do any load development, I don't hunt at long range. No keyholes.
I have mot tried heavier bullets, I use a 6.5-284 for 140's.

I shot an antelope with a 100 grain Ballistic tip at 300 yards from my 8" twist barreled 6.5x284. They stabilized fine in my gun and would shoot scary little groups.

quote:

Originally posted by ALF:
Actually when Lampel Fuerth of RWS designed the 6.5x68 circa 1940 they ran into the problem of light jacket bullets coming apart in flight with tight twist rates. Hence their decision to forgo tight twist barrels for the 1:250mm twist rate.
( 1: 9.84 inch) thus limiting the 6.5x68 in terms of bullet choice.

I had the same problem with my 6.5x.284 on an sporterized Arasaka in 1966. At the time could only successfully use 160 gr. RNs and that was a fantastic performer. roger

quote:

Originally posted by Fjold:
I shot an antelope with a 100 grain Ballistic tip at 300 yards from my 8" twist barreled 6.5x284. They stabilized fine in my gun and would shot scary little groups.

My boys both started with 6.5x55's. I loaded them 100 Gr Nosler BT's. My youngest needed a very small rifle so we used a Mexican Mauser action and a Swedish Carbine barrel with a twist rate of 200mm or 7,87". When he was 8 YO we loaded them to 2600 fps, now that he is bigger, we have run them up to 3100+ fps. Very accurate.

I've loaded 108 Lapua OTM in the 1:8 grendel with good results. They are long for weight.

Thanks, guys. I can't wait to start shooting.

I have also had great performance from an 8 twist and 100 grain B-Tips and Partitions in the 260. The 100 grain Partition at 3250 is good deer medicine.

quote:

Originally posted by Snellstrom:
The only "potential" problem is a lack of accuracy or bullet stability and keyholing.
Stability is also velocity dependant. The faster you push them the better they stabilize is the accepted norm.
I have a 6.5x55 Swede that I shoot modern loads in and it is a 1 in 8.5 twist.
It shoots 140 grain Matchkings at 2700 and 120's at 2900 and 100 grain at 3100 very well.
The fact is you can get keyboard advice out the wazoo but you don't know what YOUR rifle will like until you load for it and find its sweet spot.

Very true advice.

We have had many 223 rifles that have standard twist.

Some would stabilize 69 grain bullets, and some would not.

I have never been able to explain this.

I run a 1:8” twist 264WM and have used successfully the 85gr Ballistic Tip. Accuracy with them is the same as the heavies I run. This rifle averages 3/8 MoA in F-Class when the wind is in my favour.

Over-stabilisation is a myth, a bullet is either stable or unstable. A bullet with thin jackets or voids can, and do break up when spun beyond their yield limits, but this is rare and only effects accuracy because the bullet fails to hit the target.

Cheers.

quote:

Over-stabilisation is a myth, a bullet is either stable or unstable.

+ 1

'Overstabilization' is indeed a myth but the fact is that a bullet can be spun too fast for its length and for its form and usually manifests as lack of tractibilty, at great distance for the bullet used. That is why most shooters do not realise it exists, they do not shoot that far, there is no need to. One would have to go at least 700yds for tractibility to start being measurable.

For distance work, one would use longer bullets with a higher BC.

Of course copper hunting and copper target bullets do not fly apart, no matter how fast they are driven. A copper monolithic hunting bullet of up to 117gr can be used. The go to bullet for general hunting in a 260 Remington or a 264 WinMag is actually a 95gr HV. We have taken Kudu with it up to 400 yds and, on a lighter animal, it would be good from the muzzle out to at least 500.

In a 260 Remington with a 1:8" twist, I would use a 106gr or 117gr HV bullet.

quote:

'Overstabilization' is indeed a myth but the fact is that a bullet can be spun too fast for its length and for its form and usually manifests as lack of tractibilty, at great distance for the bullet used. That is why most shooters do not realise it exists, they do not shoot that far, there is no need to. One would have to go at least 700yds for tractibility to start being measurable.

There is opinion and there is science

Projectile stability requires that all 3 parameters of the stability condition be satisfied ! Static, dynamic and tractability!

Because you do not realize something is there or occurs does not mean it does not exist !

Tractability is inversely proportional to static stability ! Period !

The physics that dictate the gyro theorem demand this relationship just as spinning of a projectile leads to the obligatory behaviours known as precession and nutation.

As to "overstabilization" same answer !

The fact that it does not become manifest or rather has a limited effect during flat fire trajectories does not mean it's a "Myth".

It is a fact and it exists albeit at departure angles not typically associated with small arms shooting trajectories

And lastly projectile break up !

Same answer.

Hoop stress in a solid cylinder that is spun is directly proportional to angular velocity.

Spin a solid cylinder fast enough and it will fracture !

quote:

Originally posted by ALF:
[QUOTE][ . . . ]The fact that it does not become manifest or rather has a limited effect during flat fire trajectories does not mean it's a "Myth".

It is a fact and it exists albeit at departure angles not typically associated with small arms shooting trajectories [...]

I think I get what you're saying: as a phenomenon, over-stabilization exists. But it's effects would likely be (practically) nil for shooting a rifle because our rifles are more or less optimized for flat trajectory over the distances they are intended to be shot at.

But over-stabilization could be a meaningful factor in, say naval gunfire, where the projectile is intended to describe a high arc and is intended to "plunge" on it's target.

Is that approximately right?

Yep no issue until you take that same gun with its tight twist and light bullet, point it up in the sky and blast off a few celebratory shots on July the fourth ! then it becomes a issue

The forensics folks have a name for it ! Celebratory gunfire injury ! Not so uncommon as we think.


Mathematically we can deduce that over stabilization becomes a issue at angle of departure > 70 deg.

So basically in the realm of howitzers

Alf, thanks for the explanation! I appreciate it.

'Overstabilization' is a myth. It does not exist, it is a convenient misnomer for tractability.

When it comes to tractability, there is a fact that many people lose from sight. With a bullet in flight, forward motion reduces much faster than angular motion. Gyroscopic stability (Sg) increases the further you shoot. At hunting distances up to 500, with a medium calibre rifle, the angle the bullet assumes makes little difference. After that distance, it starts to count more and more. Tractability is proportional to Sg but Sg does not increase proportional to distance.

Sure, tractability is there at 500, but the same as with howitzers, we are talking about a 260 Rem and hunting distances.

Monolithic copper bullets blowing up? Yes you can make it happen in a laboratory, I suppose, at speeds and twist rates that are unattainable in real life. I have shot a 35gr HV in excess of 5000fps and a 6mm MachIV with a 62gr HV in excess of 4200fps to find the limits. The HVs just shot tight groups, no blow ups. Alf, when you manage to blow up a monolithic copper bullet in flight from a shoulder fired rifle, let me know, I would like to know about it in real life, not theory.

I shoot several different 6.5's (all 1:8 twist and have never shot anything heavier than 120 grain, but I'm just shootin deer, but never had to track one.

For a deer rifle 1.5 inch group with 3 shots is adequate out to 250 meters.

Over stabilisation is not going to affect that.

The practical reality is what you need to focus on for a deer rifle.
I AM NOT TALKING OF BENCH REST.

I would never try a 85gr bullet on deer unless it is a mono metal.

I would try the 100gr or 120gr Bal tip. You will find out very quickly. They are both listed by Nosler as hunting bullets

I have a few boxes of old Norma 77 grn softpoint 6.5 bullets. What was the intended purpose of those things?

Norma does not offer anything less than 100gr now.

My guess is that these were designed for older combination / drilling calibers for shooting smaller game like fox and may be roe deer.

quote:

Originally posted by theback40:
I have a few boxes of old Norma 77 grn softpoint 6.5 bullets. What was the intended purpose of those things?

This is what I really like about a 6.5 mm with a 1:8 twist. There are many bullets available from 100 to 160 that will shoot in it with great accuracy. I have owned several 6.5 calibers with 1:8 twist that like them all.

I have shot the 85gr Sierra varmint bullets from my 6.5x55 and it has a 1:8 twist. I didn't see any problems whatsoever.