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Maybe someone can answer this. My 1980,336 (30-30) 20in. barrel has MC rifling with a 1-10 ROT and my 2007 XLR (30-30) with 24in barrel has Ballard rifling with 1-12 ROT. I understand that in both rifles the bullet makes 2 revolutions before exiting the barrel. I guess my question is, why is there a different ROT and type of rifling?? Is the slower ROT (1-12) in a longer barrel with Ballard rifling stabilize the bullet better in the 30-30 ?? Man, I wish I was smart !!!
 

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All kinds. Enamored of their mechanisms! Worked as an engineering
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1 in 10 twist will better stabilize heavier, longer bullets than a 1 in 12. Length of barrel or bullet turns to muzzle exit are not relevant. Hope this helps. Lots of information out there regard twist rates relative to projectile stabilization. AC
 

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I don't think the type of rifling has anything to do with the twist rate really, and will take a guess that Marlin found the slightly slower twist rate stabilized the most often used bullet length/weights a little better out of the longer barrel. Perhaps because of getting somewhat higher velocities out of the 24" barrel than the more commonly used shorter lengths(?), but not an expert on the issue and guessing on their thinking at the moment. I've also read that the reason Marlin went back to the ballard rifling in many models was to make it easier for some people to use 'cast' bullets without having to get too complicated in measuring bores, bullet diameters, etc., if looking for best accuracy so to say. I think it had to do with the increase in popularity of Cowboy shoots/competitions?
 
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Found this if interested, and looks like it is somewhat tied to velocity/ammo as a factor~

"The .30-30 has always been a suitable 200 yard or so deer cartridge; Hornady’s LEVERevolution ammo extends that by about 50 yards for most hunters. According to accepted ballistics tables, the 160 grain Hornady load sighted in at 3 inches high at 100 yards is essentially dead on at 200 yards while still traveling above 1900 fps. The Marlin XLR rifle attempts to exploit this improved ammunition by elimination of the traditional barrel bands, a four inch longer barrel than standard Model 336s and, to a lesser degree, a reversion to the slightly slower twist rate (1:12) always used by Winchester, as opposed to the 1:10 twist generally found on Marlin .30-30 carbines."

Marlin Model 336 XLR Rifle
 
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The 1-12" rate of twist has more to do with the testing and development of the XLR with the Leverevolution ammo. The XLR is designed especially for the LVR ammo, probably why it came with that twist when Marlin did the testing with the LVR ammo gaining their best accuracy results. While, the regular 30-30 loads were doing "OK" in the XLR. I'm sure the Leverevolution 30-30 ammo was developed with the Marlin XLR specifically in mind, but also for use in the Winchester Model 94, which has and always had a 1-12" rate of twist. Hence the differences. Personally, I prefer the quicker 1-10" rate of twist for the regular ol' Model 336C and other Marlins in 30-30, as I know them to be more that adequate in the accuracy department. I have an XLR, but it isn't a 30-30. With my XLR, in 35 Remington, I can easily group under MOA at 100 yards. The Leverevolution ammo is accurate for the XLRs, if my 35 is any indication, but that is the only XLR that I've had any experience with.
 

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I forgot the question....I'm still looking at the pic in Scorpiusb signature section.

M
 
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30-30 ROT? No worry

All the reference data and comments above have merit in a general technical discussion.

However, I wouldn't spend time worried about 10" vs 12" twist in a 30-30.
The range of bullets you'll use (150-180 grains) at the velocities of the 30-30 (1800-2300 fps) are very narrow.
Either of these twists at 30-30 velocities will stabilize the bullets used just fine at 30-30 ranges.

Yes, a 200 grain bullet launched at 1800 fsp may yaw a bit at 500 yards....but what 30-30 shooter cares?

If we were discussing competition 30/06 shooting it could be a very different story.
The range of bullets (110-220) and velocities (1800-3500) is extreme and target distances is very broad.

For cast bullets in the 30-30, the same applies, so long as your bullet is sized .001 or .002 larger than your bore and is sufficiently hard.

Unquestionably, the 30-30 is one of the most "fun guns" around, especially when you can cast and reload for about the same as a .22 Magnum, and hunt deer and pigs with the same load.
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Load up and go shootin'!!!
 
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