Question on .30 cal. twist rates

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I have two 30 cal. rifles, a Marlin 30-30 and a TC Venture 30-06. The 30-30 id a good shooter with J-words, about 2 moa (scoped). The '06, true to Tc's claims, is just spooky accurate. Even with factory loads (150 gr. Core-Lokt) it shoots three shots touching at 100 yds. I am not disappointed with the accuracy of these rifles now that they are "cast-only". On the contrary, I am very pleased with my results so far. Both of these guns have 1:10 twist rates and after reading and re-reading threads regarding the limitations imposed by that twist rate, I ask myself the "What If" question.

What if they were 1:12 twist? Is it worth it to re-barrel to try to gain 200-300 fps? I am at 1800 fps right now with a Lyman 311041 weighing 174 grains (94-3-3 alloy) in both guns and it wasn't difficult getting there. Is 2000 within reach? 2200? If you believe what has been written about the velocity limitation of the different twist rates and trailing edge failure (I do!) 2200 may not be possible unless I decrease the twist rate. How slow a twist can still stabilize this boolit? At what speed? I certainly don't need the speed to kill corn-crunchers, 1800 seems A-OK for that! Still, the questions remain; 1:12, 1:14? Leave these puppies as-is and call it good and go build me a Boolit Gun? This retirement thing is great but sometimes I think I have too much time on my hands!

[Outpost75]

If not disappointed with their accuracy, don't fix what isn't busted!

[MUSTANG]

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I think your answer DEPENDS. Are you looking to do lots of shooting with a good accurate load; or..... are you wanting to explore many different options and validate in your own mind and for your own loads/rifle/equipment a wide variety of impacts that changes in each area results in (Seasoned Grown Up Play).

Thirty to Forty years ago my efforts were focused on how to shoot more for less to support my High Power and Pistol habit. Fifteen to Thirty years ago my focus was to inexpensively load large volumes of ammunition because the sons and their girlfriends liked to shoot (a lot) when they came to visit. The last 15 years I have switched from volume loading and "Accuracy Loading" for competition to my personal Cast and Swaged projectiles; with a focus on understanding what happens for the Internal, External and Terminal ballistics. I've read on those three areas for over 4 decades; but have come closer to UNDERSTANDING what I have read over the years based on my own testing (retesting of the work others conducted might be a better description). I can pull numerous rifles from the gun safes; prep the brass and put a Sierra Match King of the correct application and do exceptionally well (even now with deteriorating eyes); but the challenge of doing it with my own cast and swaged is a different endeavor.

Long way around the issue; but I think you may be in a similar place and the answer to the question of a new barrel with a slower twist will be found in where you personally want to go.

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Yes Mustang, I understand what you are saying. I am at the point where I no longer care to mass produce ammo but would rather build precision cartridges utilizing the boolits I created. The culls from my casting sessions are generally used for gallery loads on the indoor range during the winter. And that is fun and it keeps me from going stir-crazy during the long western NY winters. Once spring comes, then I can resume the real work, Seasoned Grown-Up Play, as you put it! It's not a case of "Is this good enough for a given purpose?" but more on the order of "What can be done?" Hmmmm.............might've just answered the question!

[NoAngel]

Outpost75 is on it. If it hits what you're aiming at and performs like you want it to, leave it alone, unless you just have money you'd like to burn for the CHANCE of something better.

Twist rates are a funny subject to me. It's important that all components and aspects of gun & load work harmoniously, but people get too hung up on cråp that means more in conversation than on paper. I have a couple of rifles that shoot well with bullets that the armchair experts say should not. What do I care, they work and work well.

You didn't mention the max distance you plan to shoot at, but the hundred yards you were shooting at.....you'll never see the benefit of wrenching out a few more FPS from a given cartridge. That sort of stuff only shows up further on out yonder. As you say, 1800 fps is sufficient to sign death warrants in your area.

Now, don't be deterred from building a custom cast bullet shooter, by all means, go for it. BUT, my opinion....start with another gun and leave the ones that already shoot well alone. That way, if the project doesn't do what you had hoped, and it does happen with some regularity, you have trusty ones on stand by.


That's just my 2¢ and with inflation....it ain't worth much.

[Victor N TN]

If it hits what you're aiming at, leave it alone. OR... if you have too much money, you can adopt me. But I come with a wife, 2 kids, 3 grandkids and 2 great grandsons.

[popper]

I get 1950 using LeverE on a 185 so yes, 2k is possible. It's not a target rifle (336 1:10) so I'd leave it alone.

[Larry Gibson]

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"What if?"

I have 30 caliber rifles with 10, 12, 13, 14, 16 and 18" twists. I have shot cast bullets extensively in them. Consider the 32 Winchester SPL; the M94 carbine has a 16" twist barrel and it has been stabilizing and shooting 170 gr bullets for 100+ years. So then why do we think a 14" twist 30-30 couldn't do the same?

The slower twist barrels in 30 caliber do, in fact allow cast bullets to be driven faster while maintaining accuracy. Given my Lyman 311041 a 14" twist will stabilize it down to 500 fps and yet at 2500 fps it maintains sub 2 moa accuracy to . A 16" twist will stabilize it down to 1200 fps. Out of my 30x60 XCB with a 16" twist 2600+ fps is very doable with excellent accuracy. Exceptional accuracy for a cast bullet of appropriate design for that level of velocity is also possible at 2900+ fps. Here's the 16" twist Broughton barreled rifle and here's a 10 shot group at 2900+ fps (the aiming diamond is .75" on a side) using the 30 XCB bullet (NOE Mould) cast of #2 alloy..

190543190544

The question of it being "worth it" to rebarrel either of those rifles can only be answered by you. Personally the Marlin 30-30 is what it is and I'd not consider any change. The TC Venture, shooting like it does, I'd also leave alone. I would look for a rifle in .308W with a 12 or 13" twist. They are still being made by Savage and Remington and others; they are completion rifles and sometimes referred to as Palma rifles.

Or I would just start with a used Savage M12 or Remington M700 in 30-06 and have it rebarreled and built to what I wanted. A sporter rifle with a Heavy sporter 26" barrel with a 14" twist chambered to 30 XCB would be excellent. If you're interesting in sheer accuracy and velocity the a heavier and longer barrel with a 16" twist is my suggestion. I recommend Broughton 3 groove barrels but a Kreiger barrel for the 14" twist would suffice nicely. I suggest chambering to 30x60 XCB or 30-06 XCB in the 16" twist barrel.

If you go that route I suggest contacting Tim Malcom of MBT over on goodsteelforums.com. He is and excellent gunsmith and can build you a cast bullet shooting rifle of which most only most dream about.

Additionally if you want to mix jacketed bullets in there for some long range shooting then a 13" twist as the slowest is advised as it will stabilize 175 MKs and 178 ELDs quite well. With a 30" barrel chambered in 30-06 XCB the bullets will remain sonic to 1400+ yards. That makes for some fun shooting also. Plus you can push your 311041 up to 2400 - 2500 fps with excellent accuracy........

Larry Gibson

[runfiverun]

switch boolit designs.

[Scharfschuetze]

This retirement thing is great but sometimes I think I have too much time on my hands!

It took me a couple of years to get fully used to retirement, but now... It's great.

Fortunately, I have an understanding wife as well as lots of rifles to shoot and play with. If you are considering a cast boolit rifle, Larry's advice is spot on. I'd PM him for the exact details on building one. I've shot his rifles a number of times at the velocities he lists above and they are just scary accurate and give not a trace of leading after several boxes of ammo down range. 300 yards? Too easy and clay pigeons at that range just disappear shot after shot after shot.

I personally like heavy bullets in my 1 in 10" twist 30 calibre rifles (Springfields, Krags and M1 Garands) at a rather pedestrian velocity of about 1,850 fps. Lyman's 311299, 311284 and 311334 all shoot very well and you might give one of those designs a try in your TC barrel.

By the way, I shoot a 195 grain cast bullet in my Model 64 Winchester 32 Special with a 1 in 16" twist and it holds just fine out to the 200 yards that I often shoot it to.

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Wow! My sincere thanks to all who responded, there's a lot to think about here! As was said, don't fix what works; I agree 100%. These two certainly shoot well enough to keep as-is. I'm gonna' look around for a long action Savage at the gun shows this spring, seems like a good place to start!

[GBertolet]

I was gifted a 30 cal Douglas barrel blank with 1-14 twist. I chambered it to 30-30 myself, for a 788 Rem. I had some doubts about stability, for my prefered 311291 bullet. My fears were unfounded, as this barrel shoots great, even at 200 yards. My current prefered load is 15 gr of 4759 @ 1520 fps. If it will stabilize bullets at this low 1520 fps, it certainly will at 2000 fps.

Normally a slower twists are kinder to minor bullet defects. Being your 1-10 twist barrel shoots great, I would leave it alone, as your cast bullets must be of pretty high quality.

[17nut]

In my 17HH 1:9 twist i have found that around 1900fps is the scatter point. Around 140000rpm.
Up through 1800fps it fine and then groups like a trumpet.

Cast from 94/3/3
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From all my cast shooting i have found that threshold is around 125-140000 rpm.
You can get (way) past that but it's walking a knives edge and you really need to know a whole lot of reloading tricks.