Velocity - Polygon rifling versus canted versus the rest

longrifle

longrifle

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Hey folks,

I don't have much experience with custom barrels and I was wondering if polygon rifling will yield a higher velocity (given everything else being equal) than a barrel with standard rifling? What about canted rifling? Thanks.


'rifle
 
I had a pac nor with polygonal rifling in 223. At its best accuracy, it didn't offer any velocity gains over other conventional rifling methods. However, that barrel went back to the shop and a new one is coming.

Will post more results when I get a chance to test. Would be nice if it does offer higher velocity WITH accuracy.

The canted barrel has many fans but never tried one myself. I think most canted barrels also come with few lands so which is the real cause - rifling or fewer lands?

Velocity varies so much due to the bore and barrel quirks that saying one style of rifling ALWAYS gives more performance over another style isn't conclusive.

Then there is the issue of ACCURATE velocity. Some barrels shoot their best at slow velocities no matter how their made.

I have had several Savage factory barrels that have shot their best at high velocities (a couple higher then the chambering suggests).

Jerry
 
Polygon rifling vs Canted vs the rest

Looking for higher velocity from a certain type of rifling is iffy at best. Various manufacturers claim some small advantages but to test this claim with "everything else being equal" is almost impossible. Polygon, Canted and other exotic rifling have been arround for years but have not made into the mainstream because of cost and questionable advantages. Adding or subtracting inches to barrel length will give you more or less velocity. Changing the type of rifling to gain velocity is ?????????????????????
 
I have a polygonally rifled barrel on my 7mm AIM, and I am getting astounding velocities out of that rifle on tiny powder charges, but I have to be honest I feel this has far more to do with the cartridge than the rifling. Is the rifling helping? Perhaps, but I'm ot about to build the same rig with a conventional barrel to find out, and as others have pointed out even if I did there are too many variables. You'd need to build dozens of rifles and average the results to see trends.
 
I've run several Rock 5R barrels (five groove radiused lands) and they had no velocity advantage over a conventional barrel.
 
The idea behind non square top lands is to reduce bore friction due to engraving. Also, offer a better seal between the jacket and the lands leaving less room for burning gases to blow by and cook the land/groove junction.

Some side benefits suggested are less jacket cutting which lead to less bullet deformation/distortion at high velocities and twist rates. All leading to accuracy at higher velocities. Nothing conclusive.

The polygonal rifling has both sides of the lands slanted. Think flat top pyramid.

Canted or R rifling just has the 'front' side canted. The opposing side is square.

All this has been played with well over 100yrs ago with such barrel greats as Whitworth. They showed some significant benefits when using lead and black powder. But then production was their biggest weakness.

Today, barrels are machined with such precision and jackets of such good alloy that I really don't see much advantage. That hasn't stopped me from buying a polygonal rifled barrel just to try out though :)

Cause you just never know. 75gr Amax going 3100+fps out of a 223 would be nice.

Jerry
 
Thanks for all the insight folks, much appreciated...mystic, the .223 idea sounds good as well!

From what I have been able to gather from the replies here and reading on various other forums, the jury seems to be out on whether or not poly/canted rifling is a benefit when seeking higher velocity. A few people have also commented that the bores of poly and canted barrels can't be properly lapped so they are rougher than finished conventional barrels, thus leading to increased fouling and decreased velocity. I guess a lapped conventional barrel may be the way to go!

'rifle
 
Actually, lapping a canted land would yield a better finish as it is easier to lap a slope then a corner. Think sweeping the dirt out of the corner of a wall. Not so easy.

The lapping slug is usually molten lead cooled in the bore so it will mimic the shape of the lands well.

All said, nothing conclusive on velocity benefits.

Jerry
 
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