Twist rate - 1-10 vs. 1-12 ...30-30 win.

[gordie]

what differences are there between these twist rates, in 30-30 ?

Marlin vs. Winchester.

[Sam Sackett]

Good question. I’m looking forward to the answers, as I recently picked up a Marlin 336 in 30/30. I’m thinking it has something to do with how heavy or long a bullet should be at certain velocities. But……. I could be wrong!

Sam Sackett

[Hick]

A faster twist will stabilize a bullet better (+1 to Marlin) but slower twist will let you run a lead bullet to a higher velocity without ripping them apart (+1 to Winchester). They are both very good in the normal range of things.

[BLAHUT]

What HICK said ! Just need to play with FPS, load, with both to get accuracy ?

[junkbug]

Also, in the earlier days, a slower twist would allow for higher velocity, without increased pressure, even with jacketed bullets. Modern powders (post WWII) helped make the faster twist more practical.

[Sam Sackett]

Ok. That explains velocity and twist rate. What about bullet weight and length? What do differing twist rates mean to them?

Sam Sackett

[TurnipEaterDown]

what differences are there between these twist rates, in 30-30 ?

Marlin vs. Winchester.

To be precise in answer: 2" of travel to get one full rotation of the bullet in flight is the difference...

No commercial producer is going to market a rifle that understabilizes commonly used bullets in a cartridge. Use what you like.
Most 30 Calibers are "over twisted" at 1:10 for commonly used bullets.
It is a carryover in my understanding from typical early 20th century military development & practices: 30-06 1:10 will stabilize 220-250gr bullets of appropriate nose profile (thus length), 8x57 Mil Mausers with 1:9.25 will stabilize 260-280 (memory on that max weight) and similarly a 7x57 1:8.25 will also stabilize very heavy for caliber bullets.

The tighter the twist, the less powder is tolerated for maximum charge, all else being equal. Energy of expansion is used to spin the bullet, thus resistance, thus the pressure curve becomes "quicker".
I have had the same chambering in guns of different twist rates, and very much find that tighter twist gets to max load quicker. Sometimes well short of book max if the change in twist is great enough from what the loading manual used.

The Greenhill formula is commonly used to find twist rate requirements. It is not exactly correct, I believe that it is empirical and conservative (won't give an unstable twist solution for inputs).
I don't think I'd be surprised if someone has updated the basic Greenhill formula in the last 25 years. I seem to remember there being free versions on line, or in some loading manual. Perhaps tables in some old manual I read in the 1990s.

The general advice that the slower twist is easier on a cast bullet is true, but I doubt that in a 30-30, unless you were shooting lighter bullets at uncommon speeds (for cast), that you would get into trouble with either twist rate.

[Sam Sackett]

Great explanation! Thanks!

Sam Sackett

[Texas by God]

Based on my experience with jacketed bullets, Marlin Micro groove rifles out shot Winchester rifles in 30-30 quite often.
That said, my most accurate 30-30 to date has a 1-10" twist- but it's a bolt action.
I think that in rifles differing only in twist; it may not matter.

Sent from my SM-A716U using Tapatalk

[stubshaft]

When T/C brought out the 30/30 barrel for Sillywett shooting and hunting it originally had a 1 in 12" twist and accuracy with heavy bullets was marginal at the 200 yard line. They quickly changed it to a 1 in 10 twist and offered to exchange the original barrels at no cost. I still have two 10" barrels with both twists. The 10 incher gets the heavies and the 12 inch barrel gets the 110 gr. to 130 gr. bunny busters.

[shooting on a shoestring]

The reason for Winchester to do the 32 Win Special was to have a slow twist, cast boolit friendly Model 94. It’s a 1:16” twist.

[John Taylor]

The reason for Winchester to do the 32 Win Special was to have a slow twist, cast boolit friendly Model 94. It’s a 1:16” twist.

The 32 Special was designed to be reloaded with smokeless or black, the reason for the slower twist. This was a carryover from 32-40 where the slower twist was believed to cause less fouling. Winchester used 1 in 12" for the 30-30 and later used the same twist in the model 70 for 30-06 and 308 with four groove rifling. The shorter barrel of the contender would need the 1 in 10 twist because of less velocity. Less velocity means slower spin. With shorter bullets and high velocity the twist can be very slow, the 50-110 had a 1 in 56" twist.

[Larry Gibson]

In lever action rifles [Marlins, Winchester's and Henry's] when using jacketed bullets there's not really any difference.

However, since this is a cast bullet forum, I'll assume the question refers to the use of cast bullets. Given conventional lubed, GC'd cast bullets of ternary alloy the difference between a 10" twist and a 12" twist is the equal accuracy level easily obtained with both and what the velocity difference will be. Has to do with the RPM Threshold. Given equal barrel lengths, the 30-30 with the 10" twist will hit the Threshold around 1950 fps. Above that velocity accuracy or even acceptable hunting accuracy, especially past 100 yards out to 200+ yards, can be difficult to attain. With the 12" twist the RPM threshold won't be reached until around 2300+ fps and very good accuracy can be attained easily out at 200+ yards and even farther.

Thus, with the 12" twist the full potential of the 30-30 cartridge can be easily attained with ternary alloy, GC'd and lubed cast bullets. Having had several Marlin 30-30s with 10" twists over the years this is the main reason now both my lever action 30-30s are Winchesters with 12" twists.

[FergusonTO35]

Hey Larry, I'm trying to develop a load with the Lee C309-170-RF for my 1985 94. Looking for around 1600-1800 fps with good accuracy with rifle powder, or 1300 with pistol/shotgun powder. Any loads you would suggest? Powders I have include Unique, AA no. 5, Reloader 7, H4198, and H335. I have a bit of 4759 but I've never had much luck with it in this cartridge and of course it can't be replaced.

[Larry Gibson]

Of the powders mentioned I'd try the RL7 first. Start at 19 gr and work up to 29 gr.

[FergusonTO35]

Thanks, will do. I figured if anybody knew a load my rifle would like it would be you!

[FergusonTO35]

Today I tried some loads with Reloder 7 and the 170 grain Lee slug. 23-24 grains looks promising. Sadly Alliant rifle powders are an endangered species around here so I'll probably have to use something else when this can runs out. H335 is pretty easy to find so I'll probably go with that one.

[Char-Gar]

In lever action rifles [Marlins, Winchester's and Henry's] when using jacketed bullets there's not really any difference.

However, since this is a cast bullet forum, I'll assume the question refers to the use of cast bullets. Given conventional lubed, GC'd cast bullets of ternary alloy the difference between a 10" twist and a 12" twist is the equal accuracy level easily obtained with both and what the velocity difference will be. Has to do with the RPM Threshold. Given equal barrel lengths, the 30-30 with the 10" twist will hit the Threshold around 1950 fps. Above that velocity accuracy or even acceptable hunting accuracy, especially past 100 yards out to 200+ yards, can be difficult to attain. With the 12" twist the RPM threshold won't be reached until around 2300+ fps and very good accuracy can be attained easily out at 200+ yards and even farther.

Thus, with the 12" twist the full potential of the 30-30 cartridge can be easily attained with ternary alloy, GC'd and lubed cast bullets. Having had several Marlin 30-30s with 10" twists over the years this is the main reason now both my lever action 30-30s are Winchesters with 12" twists.

Kids, take the above as gospel, because it is.

[FergusonTO35]

Ok, 24 grains Reloder 7 with the 170 grain Lee slug is what I'm sticking with. Just made a 1/2" clover leaf at 50 yards with my 1978 94 off shooting sticks. I really don't think I could do better even with a scoped bolt action. Unfortunately my pics won't upload here. Thanks for the good advice Larry!