hawg
Member
I've got an Obermeyer barrel on my deer rifle and it is a tack driver.
What is so special about 5R rifling?
- Thread starter Dr T
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Archie
Member
To avoid over stressing the jacket on the bullets, how about an oval bore (Lancaster) or perhaps Major Nuthall's five groove bore (much like the subject 5R rifling). (W. E.) Metford's rifling seems quite familiar, also.
Or possibly polygonal rifling. Of course, those are difficult to patent under one's own name, since they've already been in public.
Or possibly polygonal rifling. Of course, those are difficult to patent under one's own name, since they've already been in public.
Peakbagger46
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Antidotal admittedly, but my older Rem .308 5R is extremely accurate, faster than it should be, and very easy to clean.
Jim Watson
Member
H. Pope made barrels for target Krags, I assume with the same rifling plan as his Schuetzen rifles. Minimum cutting of the bullet base.
The Ruger Americans have 5 groove barrels but are not advertised as 5R. Are they, and if not, what is the difference?
FL-NC
Member
No idea. I don't know much about these types of specs, in all honesty- what I know and what matters to me the most is what I can do with a particular gun. When I can't perform to my expectations, it is a matter of determining whether its me, the gun/ammo/scope, or a combination of these factors.
Hugger-4641
Member
The older ones were not 5r, I believe they were CHF. The newer ones are 5r, thier marketing dept just doesn't seem to know it. I don't know when they made the change.
lysanderxiii
Member
"Effects of Rifling Twist, Rifling Profile, and Peak Pressure on Bore Resistance and Jacket Strain During Small Caliber Launch, " US Army Combat Capabilities Development Command Armaments Center, August 2021.
As the opportunity to develop a new cartridge only arises every few decades, it is important to examine every design variable. Finite element analysis provides a useful method for the simulation of the phenomena experienced by the bullet during launch. It allows for the analyst to rapidly change geometry, materials, and boundary conditions while being more time and cost-effective than live-fire testing. Due to this, it was decided that a comparative analysis would be performed in support of the NGFoA [Next Generation Family of Ammunition] program. Of interest to the designers was how rifling twist rate, rifling lands shape, and the pressure time curve affects the total plastic strain in the jacket and bore resistance experienced during launch.
. . . .
Testing included conventional four groove rifling profile used in the M1 and M14, six-groove rifling profile as used in the M16/M4 and five groove 5R profile rifling, all scaled to the new 6.8mm diameter. Analysis showed that the twist rate had a huge effect on the bore resistance and jacket plastic strain, which leads to a significant increase in bore resistance during the engraving process, which, in turn, will lead to increased barrel wear and possible structural integrity issues with the bullet at extreme twist rates (1-in-4 to 1-in-6).
The number of lands and the rifling profile are shown to have a minimal effect on bore resistance with any difference attributable to the ratio of engraving surface between the geometries used in this study. Generally speaking, the four groove rifling had the lowest resistance, and the six groove the highest with the 5 groove in between.
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The major advantage of polygonal rifling is that it is particularly easy to do with CHF.
The new ones are CHF also. As are the Precision Rifles which they plainly state are 5R rifled.
Reason I asked is I just picked up an American in 6.5 Grendel. Here's a picture of a land:
The edges look to be tapered so I guess that is 5R?
Archie
Member
I very much enjoy seeing the results of analysis by independent, unbiased researchers. Frankly, I'm not surprised about the number of lands and grooves having a minimal (but measurable) effect on pressure. I am a bit more surprised at the finding (increased) 'twist' having more effect on bore resistance and plastic strain on bullet jackets. I'm surprised as the late P. O. Ackley experimented on that very subject and found negligible effect. But that was eighty years ago (more or less) and jackets and testing equipment have improved. I accept the latest (seemingly in my opinion) substantial evidence on any subject.
I do have to ask if the "group" included in the testing any of the rifling patterns I listed?
Gordon
Member
A little off subject, maybe ;
I traded a nice pre 64 Winchester 70.308 rifle years ago to an active Navy Seal for "his" 9.5" Gas Trap 5.56 upper . It was "experimental" his unit beta tested and he used it a bit, evaluated it and there was no official mention of it's disposal so after a couple years I got it in mid 2000s. It has mostly stainless parts of extremely high quality finish . The 9.5" rifled portion is polygonal gain twist with about .001" choke in last inch or so of the fluted heavy profile stainless barrel . The heaviest ammo I have fed it was the Geen tip 63 grain and the Winchester Ranger 64 grain Power point both of which have produced right at 1" +- groups rested at 200 yards and with a 18x scope attached for testing. I chronographed this upper side by side with 10.5" Colt and 12" Noveske barrels installed on my Noveske Pistol lower. It was a little faster, like 75 FPS than the 13" Noveske Infidel upper , and almost 200 fps faster than the Colt 10.5" barrel that was in like new condition and was 7-1" Chromed . It is in fact as fast as 14.5 " Colt barrel I tried ! That Gas Trap upper has never given me one bit of a problem and is my cherished barrel I replaced the ridiculous 7" Noveske Diplomat upper with . It was braced the last few years but I replaced the buffer tube with the original Noveske Pistol buffer tube lately , it is my go to home defense weapon .
How can the Compak 16 fire 3 different wt. bullets?
Stabilization of bullets depends on the amount of contact of the projectile with the rifling of the bore. With our PGT polygon rifling we chose the system to allow the use of ALL the ammunition types the US military has ever put into the field.
I traded a nice pre 64 Winchester 70.308 rifle years ago to an active Navy Seal for "his" 9.5" Gas Trap 5.56 upper . It was "experimental" his unit beta tested and he used it a bit, evaluated it and there was no official mention of it's disposal so after a couple years I got it in mid 2000s. It has mostly stainless parts of extremely high quality finish . The 9.5" rifled portion is polygonal gain twist with about .001" choke in last inch or so of the fluted heavy profile stainless barrel . The heaviest ammo I have fed it was the Geen tip 63 grain and the Winchester Ranger 64 grain Power point both of which have produced right at 1" +- groups rested at 200 yards and with a 18x scope attached for testing. I chronographed this upper side by side with 10.5" Colt and 12" Noveske barrels installed on my Noveske Pistol lower. It was a little faster, like 75 FPS than the 13" Noveske Infidel upper , and almost 200 fps faster than the Colt 10.5" barrel that was in like new condition and was 7-1" Chromed . It is in fact as fast as 14.5 " Colt barrel I tried ! That Gas Trap upper has never given me one bit of a problem and is my cherished barrel I replaced the ridiculous 7" Noveske Diplomat upper with . It was braced the last few years but I replaced the buffer tube with the original Noveske Pistol buffer tube lately , it is my go to home defense weapon .
How can the Compak 16 fire 3 different wt. bullets?
Stabilization of bullets depends on the amount of contact of the projectile with the rifling of the bore. With our PGT polygon rifling we chose the system to allow the use of ALL the ammunition types the US military has ever put into the field.
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lysanderxiii
Member
This study just looked at US military "standard" 4 and 6 groove rifling and specifically 5R 5 groove rifling.
There was another study long ago that looked polygonal rifling. That rifling form produced the most strain on the bullet, as the round bullet has to be swaged into a hexagon, as opposed the just a few relatively small grooves impressed into the surface.
Archie
Member
Which raises the question, is the strain harmful, other than ultimately the increased resistance and following pressure boost?
BushMaster-15
member
Lothar Walther barrels are some of the finest made , Think Olympic Rifles and Air Rifles but they also produce High Quality center fire also .
Rifling is HAMMERED via a mandrel inside ,Broach or cut rifling and or Button Rifling could also be utilized in any of the methods for " Cleaning Up " hammer forging rifling . Manufacturers are funny and DON'T generally tell the public WHAT THEY'RE method is .
https://www.80percentarms.com/blog/cut-rifling-vs-button-rifling-and-cold-hammer-forged-barrels/
BushMaster-15
member
I used Jim’s link and spec’ed a Savage 12 26” featherweight polygon rifled barrel in a seven twist and fluted for $783.67. It said six grooves, so it’s a hexagon I fathom. I won’t know for sure, that’s too much for me.
In their custom barrel section there is a menu for choosing everything they offer. Of course, some of there options can’t be done with polygon rifling, but many can.
I am a fan of the 5R. It seemed to be an option for any AR barrel I’ve bought, so I chose it.
I don’t know if I spend less time cleaning my rifles than my associates because of the rifling, my favorite surfaces treatments(Nitride), or I just don’t spend as much time cleaning.
Ah 5R fowl ( ha ha ha hunting season ) Foul far less and the angular sides of the barrel channels reduce friction as well as the Rifling itself is substantially less surface area .
Everyone is into Speed and 5R HELPS .
lysanderxiii
Member
It does two things: 1) it increases the initial pressure rise, and 2) it absorbs energy that could otherwise be used to accelerate the bullet. It extreme cases it can weaken the bullet jacket.
Polygonal rifling is almost always hammer forged. The amount of material removed or displaced buy cutting or pulling a button through the bore would be prohibitive.
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