- January 11, 2017 at 5:54 pm #32624RobroyParticipant
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Hi folks. i got here, believe it or not, by clicking a link at cast boolits. Go figure.
I noticed the barrels of the xcb rifles are 3 groove and I believe single point cut. Why is this better for cast bullets?
My guess is that fewer grooves lead to less deformation of the bullet while still imparting spin. Wheather to cut rifling or form it by a button or hammer forging is a whole nother matter.
Thanks in advance for the answers
- January 12, 2017 at 1:41 am #32637GhostHawkParticipant
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Well I am not in the league of many of those here, but right off hand one thing appears to me.
Take a 30 caliber bore for example. 3 groove vs 5, 6 etc. Grooves and lands are going to be at or near twice as wide.
Wide would be better in my opinion for cast as you have much more metal there to resist skidding.
With perfect jacketed boolits with perfect gilding metal you probably don’t need the big lands and grooves.
With Cast I would see that as a built in advantage.
Or I could be wrong. Just a farm boy here thinking out loud.
- January 12, 2017 at 2:27 am #32643ScharfschuetzeParticipant
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It’s all above my pay grade, but I will say that three groove barrels were popular in building jacketed bullet Palma match rifles in the 80s and the 90s.
The US Military also used three groove rifles in their rifled muskets and rifles and then later in virtually all of the breech loading 50/70 and 45/70 service rifles and carbines. The three groove barrels with lead government or our cast bullets are as good as it gets with the big projectiles of these rifles.
At one time, Metford and the later Marlin Micro-Groove rifling were thought to be the best with their high number of grooves. Now? Well you don’t see this style too much anymore on recent production rifles. The British gave up on Metford rifling not because of any problem with accuracy, but due to short life with their Cordite powder.
Two groove rifling, used as an expedient in US WWII barrel production, proved to be as accurate as higher numbers of lands and grooves in government testing. My two groove 1903 rifles have always shot just as well as four and six groove barrels of like calibre in both jacketed and cast bullets.
I’ve listened to high power competitors wax lovingly over the number of grooves in their rifles while pulling targets in the pit. In the end, match winners won with rifles of all different kinds of rifling. They usually won though a combination of rifle and ammo quality as well as just plain shooing skill.
How many grooves and lands are actually better? Beats me. I think that overall barrel quality, proper fitting of the barrel, chambering as well as the appropriate rifling twist for calibre and bullet weight are all probably more important than the number of grooves.
- January 12, 2017 at 2:54 pm #32645GoodsteelKeymaster
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Actually, I’ve built XCB rifles with 3, 4, 5, and 6 groove barrels. I could see no discernible difference between them. Like so many selling points like 5R rifling, fluted barrels, crown styles, etc etc etc, I’ve found it all to be hogwash for all practical purposes. The critical things with a XCB rifle (or ANY precision rifle) are as follows in order of importance:
1. Internal barrel quality, and proper selection of twist rate.
2. Concentricity and parallelism of the entire chamber and throat.
3. A rifle properly built and fit together with extremely anal retentive attention to detail.
4. Proper, quality optics, mounted with the same attention to detail.
5. All these things put together in a balanced shooting system (literally. The rifle must balance correctly.)
6. A trigger the shooter can control well.
These things are far more important than the number and shape of grooves in the barrel. When all these things are put together properly, the edge goes to the shooter’s personal experience and prowess at the loading bench.
Thus, I find no advantage whatsoever in the number of grooves used.
In addition, I have seen no appreciable advantage to deeper rifling grooves, and I have tested that as well, side by side with new, premium barrels shot side by side with cast bullets. If one barrel shoots better than another, my opinion is that it was a better quality barrel than the runner up, or the rifle was assembled better.
- January 12, 2017 at 3:34 pm #32647Larry GibsonParticipant
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I would just add one thing to what Tim stated with regards to cast bullets at HV; The total width of the lands should be, at a minimum, right at 40% +/- of the bore circumference. The depth of the grooves should not be less than .004″. We know that the bullets will be swaged down .002 + by the lube coating the bore. There fore there must remain sufficient land height to maintain a grip on the bullet during it’s acceleration and transition down the bore.
My 16″ twist 30×60 is chambered in a Broughton 3 groove barrel. The grooves are .004 deep. Were I to have another made I would still go with the 3 groove as the 3 lands do get a very good purchase. I would also specify a .300 bore with grooves .005 deep since it would be for cast bullets only. A 26″ barrel of such chambered in 30-06 XCB should push a 311041 to 2700 fps and still maintain hunting accuracy out to 400 yards. My 31″ 30×60 pushes the 311041 to 2690 fps while holding less than 2 moa (actually 1.85″ at 100 yds for the 10 shots). Thus the larger capacity 30-06 XCB with a tudge slower powder should do that in a 26″ barrel. The accuracy may also be better with the deeper grooves.
- January 12, 2017 at 5:20 pm #32649RobroyParticipant
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Thanks again gentlemen. You’ve definately given me something to chew on.
- January 28, 2017 at 5:53 pm #33059uber7mmParticipant
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I saw a 1 groove barrel on the used rack a few years ago. It was on a ’03 Springfield in a target configuration. The clerk allowed me to look down the barrel with a white card in the open breech. Never saw anything like before or since.
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