There is a growing beleif down here in Australia among gunsmiths and F-Class shooters that 6.5 caliber rifles are less stable vertically than their 6mm, 30, and 7mm brethren.

I am a 6.5x47 Lapua built on a Tikka T3 that I shoot F-Class with, and I have noticed I have occaisional unexplained vertical fliers.

In some of the 6.5x47, 260 and 6.5x284 rifles I have seen here, this problem is much more well problematic.

Any thoughts?

Is there a way to tell if the bullets are internally concentric?

Just a wild ass guess

Good question.

Problems seem to arrise at 600 yards and beyond.

Bullets don't seem to matter nor do barrel manufacterers.

We are using Lapua, Nosler, Berger and Sierra match bullets and Madco, Krieger and Lilja barrels.

When compared to .308 caliber rifles there seems to be a tremendous amount of vertical stringing.

Bad bullets would cause larger groups both horizontally and vertically.

You probably have greater variations in velocity.

In 14 different rifles?

Is this at the same location / facility? It may be environmental.

Nope within about 800 miles.

Varying neck tension? Cases trimmed to same length?

Whose bullets, weights, velocity, twist rates, etc.
As I understand it marginally stabilized bullets can show apparent changes in B.C. as the 'settle down' with the B.C increasing as they stop yawing (tip not spinning around flight path). An increase in the coefficient would mean less drop.
Sierra has some info on this problem in one of their older books. Anyway just a thought.
C.G.B.

These are 1000 yard F-Class shooters not people that load to hunt.

I can assure you every single one of them is playing all the right cards.

Neck turn, weigh cases, weigh bullets, same case length, same chamfer, and so on.

Lapua Scenars, Sierra SMK, Nosler match doesn't matter.

The thought is growing down here that it is an awesome 300 meter CISM cartridge and beyond 600 6mm, 7mm and 30 cals are better.

quote:

Originally posted by MOA TACTICAL:
In 14 different rifles?

There is no magic. If it is not velocity it is the BC of the bullets. Is the rifling twist really adequate for those long ranges? This one area that has been heavily explored by the BPCR guys since their velocities are so low and they shoot just as far.

There is not much left once a bullet leaves the rifle if you are talking only about vertical dispersion.


Is everyone using the same superduper powder that is really untried over decades?

Are the 6.5 barrels longer and more skinny than the 30s? Meaning are they more likely to contribute to some wierd harmonic.
The opposite occurs in #1 MkIII SMLEs. They tend to group tighter at the longer ranges of 800 and 900 yards than they would indicate at 300 yards.

Everyone is shooting a 1 in 8 or 1 in 7 twist barrel and 130-140 grain bullets.

It would be interesting to see how the 140 shoots in a 1-8 versus a 130 in a 1-7.
It seems everyone copied each other right down a rat hole.

If the bullet starts yawing a little more at extreme range it will lose some BC affecting the velocity and falling short. Maybe the twist is about .5 inch too long. Sierra's ballistic guy might be able to shed some light on it.

I have worked up loads for both, my barrel is a 1 in 8.

I am shooting Lapua Scenars and SMKs. I have Nosler Match bullets but my rifle doesn't like them.

I am using a Hornady quick trickle and hornady scales so my powder measures are all exactly the same. Down to .01 of a grain.

The loads may be the same but you may still have velocity variations.

What distances do you shoot groups off a bench?

Have you tried any 10 to 20 shot groups?

What kind of scale is supposed to be good to .01 grain?

MOA I am shooting the same bullets you are out of a 6.5-06 and a totally differant type of rifle in rem 260. I have shots these rifles more than any others I have owned, but, they exhibit the same vertical anomalies your refering to. I agree there is no voodoo involved in bullet flight but I have tried many differant bullet-powder-primer combos and have yet to come up with a solution. A few shoot fine, but... I figured problem was with my methodology. Sorry your running into the same thing. shayne

F Class here (USA) is dominated by the Savage Arms Co. team shooting their F class 6.5x284.

My ancient 6.5x55 RF Sedgley deluxe sporter shoots nice round groups with any number of bullets (although throated for 160 gr RNs in 1935), 140 Bergers seated way out (30-06 length action) shoot bugholes and sub MOA to 400.

In a hot, dry place with tons of mirage vertical stringing is not unusual. Betcha you haven't tried shooting at night when it is the coolest and wind is least, just before dawn.

At this time of year in our high desert (7000") in NW Wyoming we do our paper shooting from dawn until 0800. By then the targets at only 300 are dancing up and down 6-12 inches.

Another consideration is when do your loads go subsonic although it is more of a general problem than stringing up and down.

It a'int the caliber !