Does rifling engraving affect bullet flight?

[Tommie]

Specifically...
Rate of twist, number of lands, rifling type (ratchet traditional, polygonal). I'm interested in knowing if the bullet's aerodynamics change due to engraving and if the change is predictable based upon type and rate of bore rifling.

Thanks for any input.

 

[JPeelen]

I have seen radar data for the same ammunition (.308, 169 gr) fired from two rifles with different bore dimensions.

The rifle with the tighter bore, significantly deeper grooves and a little tighter twist (11" versus 12") had a much larger variation of drag between shots than the conventional barrel. This was measured in the transonic region. At high supersonic speeds there was no perceptible difference.

I am afraid there is no simple answer to your question beyond "Yes, grooves on the bullet may have some effect, particularly below supersonic speeds." But we cannot generally say how much and in what direction. Keep away from extreme solutions, unless you have a lot of time and money for experimenting.

 

[JohnKielly]

I recall several occasions in the past where persons of an inquiring nature set out to demonstrate some particular element of shooting that had gotten the stinging insect under their headgear only to be shouted down by naysayers who demanded that their experiment be replicated tenfold.

Me, I prefer single malt.

 

[XTR]

I seem to recall reading something written where Bryan Litz has hinted that he has some data that appears to indicate that variations in rifling may have varying effects on spin decay at long ranges, though there was no conclusion associated with the comment as I recall and I have not seen any data published.

Other than that, I have seen nothing one way or the other to indicate that 5R vs traditional rifling makes any difference one way or the other. (I prefer bourbon)

 

[dcali]

Only a tiny bit, according to the military research out there. And that's rifled vs smooth, not 4 groove vs 5R (or whatever). I think it's safe to say that the practical difference between different kinds of rifling is near zero.