Groove discussion
- Thread starter SteveOak
- Start date
4 and 6 are symmetrical in that each land is opposite another, same with grooves. This is kinda considered traditional design; shape of transition can be steeper that R style.
5R is newer (I think 'Boots' Obermeyer was the originator but don't quote me on this!) where a land is opposite a groove. Transition can be less steep than the former design. Idea is there's less stress on bullets when being swaged into the rifling upon firing with the different land profile (less steep a change) and bullets may end up better balanced from the non-symmetrical land-opposing-groove bore profile.
R-style rifling seems to be less prone to collecting difficult-to-remove powder deposits too. Easier to clean.
5R is newer (I think 'Boots' Obermeyer was the originator but don't quote me on this!) where a land is opposite a groove. Transition can be less steep than the former design. Idea is there's less stress on bullets when being swaged into the rifling upon firing with the different land profile (less steep a change) and bullets may end up better balanced from the non-symmetrical land-opposing-groove bore profile.
R-style rifling seems to be less prone to collecting difficult-to-remove powder deposits too. Easier to clean.
SteveOak
Gold $$ Contributor
Thanks for the replies. They are very helpful.
Do you know or have a theory as to why the velocity is higher with the 5R? Is it due to less 'squeeze' on the bullet or somehow a greater resistance causing greater pressure such as would be caused by shooting the same load in a barrel with a faster twist?
Do you know or have a theory as to why the velocity is higher with the 5R? Is it due to less 'squeeze' on the bullet or somehow a greater resistance causing greater pressure such as would be caused by shooting the same load in a barrel with a faster twist?
Alex Wheeler
Site $$ Sponsor
I have not seen any velocity difference between a 4 or 5 groove. The 6mm is a little different. While 5r barrels seem to do well in 7mm and 30 calibers they do not seem to shoot as well as a 4 groove in the 6mm. Rock creek seems to be an exception, but their 5r is quite different, almost polygonal. I do not know much about the 6 groove Kriegers in the 6mm bore. Its an interesting topic. I really dont feel that the bullet cares how many grooves a barrel has, rather its total bore area is what matters. Bore area is why some barrels like a certain bullet better than others IMO, it effects the pressure curve. It may be that some 5r barrels have too much bore area for the bullets we shoot.
swd
Silver $$ Contributor
According to Frank Green from Bartlein the R stands for Russian from where the original design came from not Radius. They don't get any more velocity but they do seem to clean a little easier.
SteveOak
Gold $$ Contributor
Do you have a link to the articles please?
Liven The Dream
Gold $$ Contributor
The 5R from Krieger is true 5R . Boots OK'd Krieger
to make it.................. Check the web page the story is out there.
The other 5R's are not the same.
to make it.................. Check the web page the story is out there.
The other 5R's are not the same.
I would be willing to bet that 80percent of you guys that use 5r or 3groove barrels unless you slug a barrel you don't have the tools to measure actual groove dimensions on this barrels you are discussing.
The "R" does not stand for radius. It stands for Russian. Boots was the first to do it here in the States and modified it. There is no radius on the sides of the lands etc...this is often misquoted/thought so your not alone.
If memory serves me correctly he started doing it back in the '70's.
Later, Frank
Bartlein Barrels
Correct! For the most part the style or number of grooves has no bearing on velocity etc....the surface area of the bore/groove etc...will have a bigger impact on pressures and velocities as well as your throat dimensions on the reamer etc...
We've made ammunition pressure test barrels in .308win., .300wm., 6.5 Creedmoor, .338 Lapua, etc....and all the data we've gotten back from ammunition makers and the military etc...there is basically no difference in velocities etc....This is actual test data when everything else is the same except the number/style of grooves and not based off of some shooter shooting this or that.
Later, Frank
Bartlein Barrels
SteveOak
Gold $$ Contributor
Now that the groove vs velocity question has been answered, let's circle back to the original question, what is/are the reason(s) that one would choose a 4, 5R or 6 groove barrel rather than one of the others?
A personal choice, or perhaps monkey see, monkey do.
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