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6mm Remington
ATHOMSON
Member Posts: 3,399 ✭✭
I have a 6mm Remington. It's a 1/12 twist Hart 26" barrel on a M98 action. I keep reading that this twist isn't good with a heavier bullet. How bad is it with say a 100 grain? I was planning to use this as an all around rifle. Varmint to whitetail.
Thx, AT
Thx, AT
Comments
Yours may do OK, or you may have to settle on using a 80 or 90gr bullet instead.
"I have a 6mm Remington. It's a 1/12 twist Hart 26" barrel on a M98 action. I keep reading that this twist isn't good with a heavier bullet."
Twist rate is calculated by the length, diameter and velocity of a given bullet. Look up the Greenhill formula.
This is the same mistake that Remington made when they originally introduced the .244 Remington (6mm Rem.) in 1955. They used a 1:12" twist thinking that this would be the ultimate varmint cartridge so the need for a faster twist wasn't there. Winchester brought out the .243 Winchester with a 1:10" twist which was capable of using the heavier 90 and 100 grain bullets suited to hunting deer. Shooters flocked to the .243 Win. because of the ability to use it as an all-around rifle. The .244 Rem. languished because of the misstep by Remington.
There are a couple of shorter 90 and 100 grain roundnose bullets that can be used for deer hunting as long as you keep the muzzle velocity up near the maximum. Speer makes a 90 gr. Spitzer that will work right along with the 87 gr. Hornady Spitzer. But if you have thoughts of using the longer, pointier, boattail bullets, you need to sell your rifle and get another one with the proper twist rate.
Best.
AT
The twist you have may or may not stabilize a 100 gr. bullet. To get it to stabilize you will definitely need to be near the top velocity of 3100 fps.
According to the velocity formula, which is a modification of the Greenhill, nononsense spoke of, 3000 fps will require a 1-10.6" twist to stabilize a 100 gr. bullet that runs 1" in length. 1-12" is close enough usually to stabilize that length.
A little side note to this. The formula is close but not dead on. It gives the "center" of the range in which a bullet will stabilize. Some bullets are inherently more stable. Something I think I've found with this is to find the length of the bullet weight, not just the length of the bullet. I've noted that some VLD's and ULD's I've shot that have a hollow tip stabilize at lower speeds than their counterparts with a soft lead tip. Meaning the actual length of weight in a soft lead tip is longer than the VLD with the shorter lead weight but longer overall length.
So, I recommend you try Nosler 95 gr. bullets and Berger 95 gr. bullets and see how they may work in your rifle. The 6mm is a great caliber. FWIW I've shot a lot of deer with an 85 gr. bullet out of a .243 at slower speeds than what your 6mm will do.
There is nothing a 100 grain 6mm will do to a deer that a 95 or even 85 grain Nosler Partition won't do as well or better. Load 'em up.
Rifling twist is overstudied these days and Greenhill is a VERY rough approximation of what is needed with a Mach 2+ spitzer.
I mention the Greenhill formula in a VERY GENERAL discussion as a guide to help with a simple understanding for this discussion and all of a sudden it's value is diminished in favor of nothing better.
The Greenhill formula has always been a shortcut to allow us to arrive at a simple answer without using several days of advanced mathematics to solve the more complex relationships required to design a bullet and determine the twist rate required for that bullet. And before you correct me again, yes, computers save us a significant amount of time.
The original formula as developed by Sir Alfred Greenhill in 1879 was used to solve artillery problems and had nothing to do with small arms until later. So yes, you might say it is a little rough but in all cases it is a generically usable answer that requires very little effort and significantly less math. We have improved the answers since we currently use the constant of 180 instead of the original 150, to better simulate an answer for higher velocities encountered today. It's still better than nothing but not as accurate and detailed as the corrected formula below.
The actual formula is much more complicated. It is Gyroscopic Stability (GS) = the spin rate (in radians per second, squared) times the polar moment of inertia, squared, divided by the pitching moment coefficient derivative per sine of the angle of attack times the transverse moment of inertia times the air density times the velocity squared.
Now, before you ask me to solve anything using this formula, I have it on my computers and I borrowed this written description from a friend of mine that helps me solve some of these things while I work on the physical resolutions. I can wade through the math but he's much faster than I am. Personally, I'll stick with the modified Greenhill formula since it's all that's necessary for a quick idea of a twist rate and save my time for more important things.
As I end up stating as a disclaimer more frequently these days, there are exceptions to all things. This formula and the resulting answers follow the same concept, there will always be exceptions. For the sake of simplicity though it works just fine.
Best.
We sometimes tend to attempt to split hairs with a maul.
What I'm merely suggesting is that while some VLD and ballistic tip bullets are longer than their lead core/tipped counterparts they may stabilize when a similar bullet of an older style construction will not. Not that the Greenhill is not a good reference to get you where you need to be roughly with a rate of twist for a length of bullet.
I agree it could be much more complex than it needs to be if we were consistently trying to gain the ultimate in accuracy. All of the factors could be micro-studied to death and we would gain little without all of those factors being applied at the line in the micro-second they became applicable. In this case we are simply looking for stability. I think it could be attained in the 1-12" twist at max speed with a Berger 95 or a Nosler 95 gr.
I have a 6mm with a Shilen 26 inch barrel on a VZ24 M98 action. Mine is a 1:10 twist. [^] It shoots everything from 55 to 105 gr. pills very well. It's optimal (I believe) using 80 through 95 gr. bullets.
For hunting Antelope or Whitetail Deer, I'd try the 85 Nosler Partition or the 85 gr. Hornady Interbond or the Hornady 87 gr. Spire Point or the Speer 85 Grain Spitzer. My father has a M98 6mm with a Douglas 24" sporter with 1-12 twist. We found the 85 Nosler and Hornady's 87 in both SP and HPBT shoot very well in his. [8D]
BTW: When Remington realized the popularity of the 244 Rem. was lesser than the 243 Winchester[B)] they changed the twist of their rifles to I believe 1-9 and renamed the cartridge 6mm Remington. Factory loadings for the 244 Remington were 75 gr. and 90 gr.; the 6mm were 80 gr. and 100 gr.
Vic
Thx, AT
I gotta say that if you're going to shoot a lot then reloading is the only way to go. The price of ammo has gone through the roof! Sometimes you can find components for a reasonable price when bought in bulk that will help keep it 'less expensive'. That's a relative term. Even when buying compnents though you still get quite a break over buying bullets.
Great! You're off and running. Your next post is already getting more suggestions for combinations of components and more encouragement. I think you and your sons will enjoy the entire process of research, reloading and shooting.
Best.
sandwarrior,
I understand where you're trying to go and to a small extent velocity does play a role. My disagreement here is that you can't get velocity to stretch that extra 1-1/2" to 2" of twist. I double checked my notes for several rifles, several cartridges and even the top 3 types of rifling forms and the oblong holes in some targets indicated that the Berger 95 gr. VLD bullets needed at least a 1:10 twist at upper end CONSTANT velocities. A real quick phone call to Eric Strecker at Berger confirmed this. He suggests a 1:9" twist to cover their b_ _ _ _ when folks want to use the 6mmBR case at 2900+ FPS.
Theories are great, that's what keeps all of us running tests and asking questions.
As far as the air space theory in the nose of some bullet designs, you might want to talk to Henry Childs at either Benchrest.com or 6mmBR.com. He ran some tests a few years ago that might have some bearing on your thinking. He has always been very helpful in working out things like this as far as I was concerned.
Best.
Thanks for the tip on Henry Childs. I do agree with you that for the most part velocity is not going to get the job done. Unless that is, you are right on the verge of stability and a little more push will help. As is typical though, the little extra push sometimes spreads groups out. So it might not do any good to do that. Sticking with the right bullet for the twist you have is simply the easiest way to know you're in the clear. In this case the 75-90 gr. bullets will do the best without much headache of trying to find a better faster load.
I suggested the use of them as I was able to stabilize both the Berger and Nosler at 2800 fps from a 1-10" twist*. 2" more to make a full twist might well be the killer on that idea though.
edit: * I noted I had a good group from this but didn't look to see how round the holes were. Sometimes I don't pay enough attention to that. Looking at my targets the next day I see things like that.