OzFclass

Brains trust,

223 for F standard using 80gr Berger VLD target.

Berger website and box says minimum 8T

The Berger website calculator tool for the approx FPS and twist rate of 8T throws an SG of 1.36 to 1.45 depending on temp (22 deg being the lowest - 40 being the highest)

Now the issue is availability of a 7T barrel where there is several 8T barrels available to me.

Ill be shooting to 700m maximum with this rifle, looking to be competitive but mostly used for cheaper trigger time and as a trainer.

QUESTION - Albeit on the upper end of marginal stability (according to the calculator) how much of a disadvantage would the 8T be over a 7T which on the same calculations completely stabilizes the bullet to its full BC value. What will be the real world consequences for going the slower 8 twist over a 7 twist.

Thanks in advance.

all being well, 1.4 will not be bad.
BUT. (yes that word)
if something less than ideal appears in the weather, unforeseen things can happen.
barometer shows higher pressure, and then the bullet goes through a wind shear situation, an out of character shot might appear on the target.
as the bullet goes through the wind shear barely stable it will be forced to precess and nutate again prior to going to sleep again, if it has time prior to meeting the target.
our long range bullets are prone to tending to steer themselves where their axis points to some degree.
this of course puts the bullet in a different condition the the previous one.
quartering winds can cause similar issues.
do not be concerned about going with an s.g. of 1.6 or more for preference.
I have fired bullets at s.g. over 2.0 with no problems.
s.g. is gyroscopic stability.
there is also dynamic stability which can vary with bullet design, and might require faster spin rates than for s.g.
bruce.

["bruce moulds"]

Thats great information Bruce! Thanks for taking the time to pass that knowledge on, looks like a 7.5 twist will be the sweet spot.

Also consider that Berger is bringing out an 85.5gn hybrid which should be great in 223 and this would be even more suited to 7” as are the 90gn Sierra’s which might would be worth a try. I think more Bartleins are due to arrive in the next few weeks and there might be a 7” in that run?