OzFclass

I'm considering using the 5R rifling profile for my next match rifle barrel, just for the sake of a change, something along the lines of a 10 twist 32" .30 calibre probably from Krieger.

I have seen results from one barrel of this rifling configuration but another manufacture which achieved above the odds velocity for powder used, which is encouraging for my application. To the contrary, I have read anecdotal reports suggesting that the extra land surface area is deleterious in certain respects, whatever & however arcanely that was calculated. Vexingly, there are arguments as to whether the different intrusion into the cross sectional profile of the projectile results in a more or less desirable ballistic outcome. And the story goes on....

Does anybody have any hard information based on factual outcomes, preferably personal?

John Kielly

john,
i have used both, and am happy with both canted and square lands.
buy it and try it.
you will probably find that you are like me, quie catholic in your tastes.
there has been a lot of hype about 5r, both positive and negative. that is all it is - hype.
the next consideration is whether or not to include gaintwist in the formula.
apparrently a gain of about 1/2" in the length of a barrel acts like a choke in improving velocity s.d.
keep safe,
bruce.

The reduced land form was born from Boots Obermeyer's experiments with a high velocity calibre
that resulted in the odd lost bullet ala blue screamers.
He changed the land form and the lost bullets stopped.
I think the velocity was in the region of 3600
(can lookup the correspondence) so doubt it applies to MR.

In terms of gain twist, it is the absence of negative twist
which is more important and which occurs in a button barrel if the button slips.