OzFclass

Have a couple of interesting things. One was pointed out to me about 1.5 years ago and pretty much the same thing was told to me last Friday by another gun manufacturer/ammo maker as well. Both places don't talk to one another or do any testing together etc...so I rule out conspiracy theory things. LOL!

What has been told to me is basically this. The stability of the bullet in bore (while inside the barrel) that the 5R rifling gives more radial support vs. conventional type rifling (like a standard 4 groove, 6 groove etc...) and that this helps the accuracy of the bullet. This test was performed with almost 50 barrels just in 5R rifling. They had a similar number of barrels with the standard spec. 6 groove rifling. The 6 groove rifling had issues where the 5R didn't. They told me the 5R rifling really showed it to help with the hybrid/secant type bullets but those bullets in the 6 groove is where they seen the performance issues.

About a1.5 years ago a test was done by accident. It was doppler radar testing and they had a 6.5mm barrels both in 4 groove and 5R rifling. The bullets out of the 5R rifled barrel flew with no issues till after they went subsonic but the 4 groove barrel when the bullet was crossing the transonic range around 800 yards would fly erratically for a brief moment and then settle back down. This ammo/bullet maker has ordered more barrels to run a larger test/sample size if you want to call it that to confirm what they are seeing.

Later, Frank

In my mind the profile of a tapered land acts more like a dovetail on a lathe. Interested to hear your thoughts frank but when you cut rifle barrels a tool cutting a 5R barrel would be cutting on (hopefully) all 3 sides of the cutter so the groove should stay uniform width as well as depth? Conventional rifling is only being cut at the bottom of the groove so it would be more difficult to control it's width? Similar would apply to the lapping process and also when the bullet is traveling down the barrel.

BATattack wrote:In my mind the profile of a tapered land acts more like a dovetail on a lathe. Interested to hear your thoughts frank but when you cut rifle barrels a tool cutting a 5R barrel would be cutting on (hopefully) all 3 sides of the cutter so the groove should stay uniform width as well as depth? Conventional rifling is only being cut at the bottom of the groove so it would be more difficult to control it's width? Similar would apply to the lapping process and also when the bullet is traveling down the barrel.

BATattack, I understand what your getting at....but I'll say conventional rifling or 5r style....the cutting tool is cutting not just the bottom of the groove but the sides as well. We'd be splitting hairs but I would agree that to some extent that rifling the 5R style would stay a tad more uniform than a 4 groove or 6 groove etc...

Finish lapping the bore...I always say...it's meant as a final polish/finish per say in the bore. You will take say a .0001" to .0002" out. Some barrel makers will finish lap to achieve the final size/dimensions of the bore. This should not be done. It's impossible to control in my opinion. I know of barrel makers that will finish lap and try and take a full .001" out of the bore. When they do this....it's not good in the long run.

bruce moulds wrote:pete,
that is probably better than one with a kink in it where they "straightened" it, as was done in the day.
bruce.

You mean as Savage still do. lol.