In a given caliber, as you speed up the twist, are better balanced or more precise bullets required for accuracy? Another way of framing the question is: are slow twist barrels less sensitive to out of balance bullets?

No. The only real difference is that faster twist barrels will stabilize longer (heavier) projectiles, while slower twist barrels will not.


This is conjecture on my part, but faster twist barrels might actually do a little better with less precisely made and balanced bullets.

https://www.everydaymarksman.c.../rifling-twist-rate/

It depends a fair amount. There are generalizations with certain cartridges, then can get a little specialized.

According to the ballistician Bryan Litz, the faster the twist and spin rate, the more imperfections and irregularities in the bullet adversely affect precision. He says that benchrest shooters who strive for maximum precision (tiny groups) at relatively close distances usually shoot short, flat base bullets because they require slower twists to be stabilized.

On the other hand, precision shooters who are concerned about hitting small targets at long ranges choose bullets with high ballistic coefficients for flatter trajectories and to minimize wind drift. High BC bullets with their sharp noses and boattail designs are longer and therefore require faster twist rates to be stabilized. For those shooters the requirement for fast rifling twist rates to stabilize long, high BC bullets is more important than any precision advantage of slower rates. There would, though, be no benefit to a faster rate than required for whatever bullet one was shooting as long as it was enough for various environmental conditions.

But then, perhaps it’s not all that simple.
The usual twist rate for rifles chambered for the 22 Long Rifle cartridge and with 40 grain round nose bullets is 1/16". I have seen a bit of discussion that some precision shooters are experimenting with 1/14 or even 1/12 inch rates. What the status of that experimenting is, I haven’t tried to determine, but as I recall one man who builds extremely high quality 22LR rifles says he doesn’t believe there is any advantage to faster rifling rates. In any event I have much more confidence that Litz knows what he’s talking about when it comes to centerfire cartridges.

This would make for an interesting experiment. You'd need to identify the less perfect bullets in a given lott by one or more measurements. How would you determine what constitutes enough of a standard deviation from spec that the bullet would now be classified as a less precisely made bullet? Would that be by weight, run out, ogive deformity, or something else I can't think of right now?

quote:

Originally posted by SgtGold:
This would make for an interesting experiment.

Yes, it would.
I can’t think of any other factors than the ones you mention, other than perhaps(?) bullet length and some sort of meplat measurement. Then of course it would be necessary to have otherwise identical barrels except for rifling twist rate, and for most of us mortals that would be a major issue.

Now that you mention it, I don’t know how Litz reached his conclusion, i.e., was it based on hard empirical data or just theory? Knowing the other sorts of experiments he has conducted and documented in his series of books, it could very well be the former, but I don’t recall that was stated.

But then perhaps the generations of benchrest shooters with their never-ending quests for precision have already answered the question. Although it wouldn’t be the same as formal side-by-side comparison tests, the fact, for example, that every top BR shooter using the 6mm PPC cartridge also used a particular barrel twist rate that was slower than what less-successful shooters used would pretty well confirm the fact. Could a conclusion like that be based on something other than the relationship between twist rate and bullet imperfections? Possibly, I suppose, but unlikely, it seems to me.