Any suggestions on proper twist for 9.3X62...250gr, 286gr

Mine is a 1/12" and 286gr Barnes X's will go under an 1" at 100 yds.

hth

My three 9,3's are 1-14".

Blaser 9,3x62's are 1-11".

Anywhere from a 10-14" will serve you just fine. I use 12" myself and have never had a problem with ANY 9.3mm bullet I've used...

1-12"

1-14" is not as accurate as I would like with 320 grain bullets, hence my preference for 1-12.

quote:

Originally posted by Rick R:
Mine is a 1/12" and 286gr Barnes X's will go under an 1" at 100 yds.

The quality of the barrel is more important than the marginal changes in the twist rate. High precision barrels imply, straightness of barrel, uniformity of bore diameter, uniformity of twist rate throughout the length of the barrel, equal depth of groove throughout the length of the barrel, a perfect crown at the muzzle, quality of chamber and its line-up with the bore and no leeway in the 'headspace'. When the twist rate shows itself to be a problem, by then bullets will exhibit 'keyholing' on the target or even tumbling.

I tested the rather long-for-caliber 325 gr Rhino Solid Shank bullet, 300 gr Swift A-Frame bullet and the 285 gr CDP (Swiss made) bullet with Pieter Olivier and there was no sign of instability with any of these bullets both in his CZ550 rifle and my Husky, both with 1-in-14" barrels. It is true though that barrels have their own idiosyncrasies and the same twist barrel (from different manufacturers typically) may perform different with the same bullet. Bullets of different makes differ in concentricity, evenness of wall thicknesses, type of metal and therefore engraving resistance, length of bearing surface and different construction. These things alone change the accuracy equation. When we add differing length, COG and specific gravity of bullets, the twist rate come directly into play, as this composite situation (the make-up of the bullet) will need to be stabilized.

The 9,3 x 62 mm has earned its reputation with its standard CIP twist rate of 1-in14". If a 286-gr Barnes-X bullet can give a 1-inch group, being a long copper bullet with a lower specific gravity than a lead core bullet, I would submit that it is a moot exercise to step up the twist rate in the believe that it is the only variable or the magic one.

Overly long bullets such as the 286 gr Barnes-X bullet only rob powder space in a cartridge case that is not known for achieving high velocities, and that is why I use the 250 gr Barnes-X bullet that I can launch faster, being a Spitzer with a better BC than those heavy RN bullets, to give me a better trajectory. When the trajectory is not that important I prefer to use 286 gr Rhino bullet, which is a Semi Spitzer bullet. My friend Pieter Olivier prefer the 300 gr Rhino RN, and now more recently the 325 gr Rhino RN configuration for buffalo at short range as trajectory is the last of one's worries.

Chris

quote:

Originally posted by 500grains:
1-14" is not as accurate as I would like with 320 grain bullets, hence my preference for 1-12.

Just out of curiousity, why are you convinced that the twist was the problem, and not some other reloading factor?

Thanks all, I've decided on one of Doug Shilen's 1 in 12

Good call!

N E 450, are you sure ? My Blaser 9,3x62 goes 1-14".

Just like to share this tid-bit of info ...

Target shooters or benchrest shooters lean towards slower twists, as they focus more on stability in air (closer to 'Just stable' condition SF=1.0)rather than hunters that typically opt for faster twists with a SF condition of between 1.3 and 1.5 with terminal performance in mind. Reason being that an 'over-twist' accentuates a wobble in a less than perfect bullet. Very few bullets are perfect in the true sense of the word.

Truvelo of SA make their .308 target barrel with a 1-in-12.5", optimised for the sleek 155 gr Palma bullet. Typically, most 308 Win's have a 12.0" twist as opposed to a 30-06 Spr that features a 10" twist. I do not know of anyone that would compete with a 308 Win that has a faster twist, such as a 1-in-10". That should tell the story.

Take care
Chris

quote:

Originally posted by Andre Mertens:
N E 450, are you sure ? My Blaser 9,3x62 goes 1-14".

My did too.

My friend just returned from a trip near the Kruger Park, where he guided 3 French hunters. He came over tonight for dinner to share all the hunting stories.

Amongst others, he told me he got 8 mm groupings with Woodleigh's 320-gr SN bullet at the range in his 9,3 CZ 550.(1-in-14" twist)

What was amazing was that it yielded the best accuracy of all the different makes of bullets, including all the lighter ones, that he tested in his rifle so far.

Curious to know what the stability factor would be of the Wdl 320 grainer, I dedcided to calculate its SF value. Based on a sg of 9.9 it came to 1.92 and that is way beyond the stability in air condition(SF = 1.0), which then lay to rest the notion of a 14" twist barrel being too slow.

Chris