I recently worked up some lead free loads for my Thompson/Center Encore Pro Hunter in 7mm Rem Mag. I used 150gr Nosler E-tip with 64 gr of RE-22 behind it. It produces about 1" to 1 1/4 groups at 110 yrds. Just fine for hunting but im a bit obsessed with accuracy so I asked a guy next to me if he knew much about loading for lead free. He told me that the best thing to do was to shoot lighter bullets. He went on to say that if I dropped down to a 139 or 140 gr bullet that my groups would be under 1/2". He also went on to tell me that they would produce much better kills on deer and larger sized game because the bullet would be moving much faster and therefore it would shrapnel more on impact instead of the heavier ones just punching right through. Any of you guys have any input on this?
Reloading lead free
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Unless you are playing with the twist (say going from 1:10"to 1:12" ) I would think lighter bullets would be less accurate.I am not familiar with LF bullets but find going light in fast twist barrels either doesn't improve or lessens the accuracy.The best twist for a given bullet is just enough to stabilise in my book.I see Savage is using a 1:9.5"twist which in MHO would make it even worse for light bullets and pinpoint accuracy.Would love to be corrected if I am thinking wrong. I had a post on this and went advanced and it didn't work.I'll try this. ,,,sam.
If you are reading this the only way it works is with a quote advanced doesnt work either ,,,sam.
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well im defiantly no expert but the barrens triple shock i use has to add length to get the weight to add to the stability problem
Thats right,and basically the longer the bullet,the better it stabilises going through the atmosphere. ,,,sam.
Dad is working with some lead free bullets, I can't say what kind off the top of my head, but he says for the same bullet weights they are longer than ones with lead in them, and he also says that to stabilize them they need to be shot in a faster twist barrel according to the manufacturer
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THE GREENHILL FORMULA
Twist is measured in the number of inches for one complete turn of the rifling in the barrel. For example, many 30 caliber rifles have barrels with a twist of one turn in 10 inches.
For a given twist rate and diameter, there is a maximum length of bullet that may be stabilized.
If the bullet is too long, or the twist is too slow, the bullet will not stabilize and will go through the target making a hole that is somewhere between oval and the side view of the bullet.
When the bullet makes an oval hole, we say that it is “tipping”. When the hole starts to be real long and to look like a side view of the bullet, we say that the bullet is “keyholing”. It is not uncommon to find that best accuracy at slow velocities is accompanied by slight tipping of the bullet. (Tipping is also called "yawing")
The Greenhill formula was designed around the stability = the ability to keep the sharp end going frontward, of low velocity lead bullets.
Bullet stability is affected by several variables not included in the Greenhill formula.
Bullet stability is slightly affected by velocity, faster bullets are slightly more stable than slower.
Stability is affected by bullet density; an aluminum bullet won't be stable at Greenhill length and linotype (less dense) bullets are less stable than lead bullets.
Stability is affected by the density of the medium the bullet is going through-generally air, but sometimes meat or water. Bullets are slightly more stable at high altitudes where the air is thin, than at sea level; and are much less stable going through denser mediums such as meat or water. Most of the time Greenhill does a remarkably good job of explaining the relationship between caliber, twist and bullet length required for bullet stability.
The Greenhill formula is an approximation showing the relationship between rifling twist rate, maximum bullet length, and caliber. For any caliber and twist there is a maximum bullet length that will stabilize. For any caliber and bullet length there is a minimum rifling twist that will stabilize that bullet. By algebraic fiddling we can solve for either twist or length. Here is the formula set up to solve for maximum bullet length.
The Greenhill Formula is: L = (150/twist) * (caliber squared)
Where L is the maximum length of bullet that will be stabilized in inches; twist is the number of inches required for one turn in the rifling; and caliber is the bullet diameter in inches.
This table shows the maximum bullet length by caliber/twist combinations. For example, a .308 caliber barrel of 10" twist will stabilize a bullet that is a maximum of 1.42" long.
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I've been working on a load using the Barnes TSX 300gr in my 405.
There is an article that leaves a lot of variables lying in the open.They give no credibility to difference in velocity and yet it is a key factor.A .300Savage needs a faster twist to stabilise the same weight/length bullet that is stabilised easily using a .300WM. 800 to 1000fps makes a big difference in the RPM,s being turned.It is only RPM,s that stabilise,well,that and atmosphere. (as long as density is the same) ,,,sam.
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Chapter 2.3 Twist - Cast Bullets For Beginner And Expert
this is the whole article but what you are saying makes sense
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I have shot the Barnes 140gr and 150gr Triple shock bullets from my 280AI which is a few hundred fps slower than your 7mm Rem Mag. I have found them to shoot very well out of my rifle. The accuracy is right in line with other bullets. I have no experience with the Nosler E tips though so i'm not sure they perform the same. The Barnes bullets are designed not to fragment so in theory you don't need a heavier bullet to see deep penetration. With standard bullets you can lose up to 50% of the bullets original weight so a heavier bullet would be used to get deeper penetration. With the Barnes bullet retaining nearly 100% it will weigh the same and therefore perform better on penetration.
As for the twist rates, due to the bullets being longer to achieve the bullets weight you might need a little faster twist to stabilize a bullet. One important thing to do before you shoot a copper bullet is to clean clean clean your barrel and make sure you have all the copper fouling and other crud from your barrel. I have noticed a big improvement when I cleaned my barrel really good before shooting the barnes bullets vs not cleaning.
As for the twist rates, due to the bullets being longer to achieve the bullets weight you might need a little faster twist to stabilize a bullet. One important thing to do before you shoot a copper bullet is to clean clean clean your barrel and make sure you have all the copper fouling and other crud from your barrel. I have noticed a big improvement when I cleaned my barrel really good before shooting the barnes bullets vs not cleaning.
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I bought some 62gr Barnes Varmint Grenades for my .243...it has a 1-9.25" twist. They should work just fine because from what I understand the bullets length affects what twist rate it needs...so I'm think a 62gr lead free should work fine in a 1-9.25" twist barrel...I also use 250gr Barnes expander bullets in my muzzleloader.
It is rotational velocity that effects stability, not forward velocity. Hence at the same forward velocity, the longer bullet needs a higher rotational velocity to stay stable. If the twist is the same, the longer bullet must move forward faster to obtain the higher rotational velocity.
It is rotational velocity that effects stability,not forward velocity.-----If the twist is the same the longer bullet must move "FORWARD" faster to obtain the higher rotational velocity.-----Confusion,confusion,is forward velocity important or isn't it????? ,,,sam.
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stabilizing longer lead-free bullets
bullets of the same length require the same RPM.
if a given twist rate is used they just need to travel thru the barrel in the same amount of time, thereby imparting the same RPM.
if the weights (technically we should be talking mass, but still...) are the different a larger charge maybe needed to propel the more massive bullet thru the barrel in the same time, yielding the same RPM. Inertia requires a larger force to move the larger mass to the same speed.
but the lead free bullets (of approx same weight) are longer than the non-lead free. But in practice, in my gun, both are over the RPM requirements and stabilize. In other words, the RPM requirement is moot because both are spinning faster than the min. RPM needed.
I loaded 7mm 139 gr Hornady GMX (lead free) bullets with the same charge as 140 gr CoreLokt. My barrel has 1 in 9 1/2 twist. I don't have a cronie, but velocity should be about 2600 fps for this particular load. The GMX shoot 1/2 moa and the CoreLokt just over that. The GMX lead free are longer than the CoreLokt but they seem to stabilize nicely.
theory says the longer bullets should require more RPM but I think with this twist both have sufficient RPM to stabilize, i.e., both bullets respectively are over the required RPM for the bullet stability.
bullets of the same length require the same RPM.
if a given twist rate is used they just need to travel thru the barrel in the same amount of time, thereby imparting the same RPM.
if the weights (technically we should be talking mass, but still...) are the different a larger charge maybe needed to propel the more massive bullet thru the barrel in the same time, yielding the same RPM. Inertia requires a larger force to move the larger mass to the same speed.
but the lead free bullets (of approx same weight) are longer than the non-lead free. But in practice, in my gun, both are over the RPM requirements and stabilize. In other words, the RPM requirement is moot because both are spinning faster than the min. RPM needed.
I loaded 7mm 139 gr Hornady GMX (lead free) bullets with the same charge as 140 gr CoreLokt. My barrel has 1 in 9 1/2 twist. I don't have a cronie, but velocity should be about 2600 fps for this particular load. The GMX shoot 1/2 moa and the CoreLokt just over that. The GMX lead free are longer than the CoreLokt but they seem to stabilize nicely.
theory says the longer bullets should require more RPM but I think with this twist both have sufficient RPM to stabilize, i.e., both bullets respectively are over the required RPM for the bullet stability.
Still,the best way to go is contact the bullet MFG,r and ask.This gives the formula. ,,,Calculating Bullet RPM — Spin Rates and Stability AccurateShooter.com Bulletin ,,,sam.
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Unless made of Uranium or something else with a density greater than that of lead, LF bullets will be longer than a lead bullet of the same weight. Polymer inserts in the nose add even more length and very little weight. There are two links from earlier threads which should prove interesting to you guys.
The first, telling why bullets do what they do is http://www.bordeninstitute.army.mil/published_volumes/conventional_warfare/chapter4/Pages1-12.pdf. This is one chapter of a somewhat longer volume on wound ballistics that is primarily intended to explain why bullets act like they do in soft tissue, but it does a nice job of explaining why they act like they do in air also.
The second one, of more practical value, is also a part of a longer document. You can find it at http://www.stevespages.com/page8e.htm. This one contains lots of tables in which you can look up your caliber, velocity, bullet length (notice there is nothing about weight, just length), and rate of twist to narrow down just how fast you should push bullet X in barrel Y to maximize the accuracy.
There is a school of thought that says you can spin a bullet too fast and lose accuracy, but I have yet to see an explanation of just why that occurs. A faster twist can cause a drop in velocity over a slower one with the same load, but I don't understand why it should give a loss of accuracy. The reduced velocity means there is a bit less rpm than if it was at the higher velocity, but I don't think the velocity loss will compensate for the faster twist -- in other words, even though a bullet is travelling a bit slower from a faster twist barrel, it is still spinning faster than if it was fired through a slower twist barrel at a greater velocity.
If someone can post a link to explain the "spin it too fast and you lose accuracy" idea as well as the first link up above explains the importance of length to spin, I would appreciate reading it.
The first, telling why bullets do what they do is http://www.bordeninstitute.army.mil/published_volumes/conventional_warfare/chapter4/Pages1-12.pdf. This is one chapter of a somewhat longer volume on wound ballistics that is primarily intended to explain why bullets act like they do in soft tissue, but it does a nice job of explaining why they act like they do in air also.
The second one, of more practical value, is also a part of a longer document. You can find it at http://www.stevespages.com/page8e.htm. This one contains lots of tables in which you can look up your caliber, velocity, bullet length (notice there is nothing about weight, just length), and rate of twist to narrow down just how fast you should push bullet X in barrel Y to maximize the accuracy.
There is a school of thought that says you can spin a bullet too fast and lose accuracy, but I have yet to see an explanation of just why that occurs. A faster twist can cause a drop in velocity over a slower one with the same load, but I don't understand why it should give a loss of accuracy. The reduced velocity means there is a bit less rpm than if it was at the higher velocity, but I don't think the velocity loss will compensate for the faster twist -- in other words, even though a bullet is travelling a bit slower from a faster twist barrel, it is still spinning faster than if it was fired through a slower twist barrel at a greater velocity.
If someone can post a link to explain the "spin it too fast and you lose accuracy" idea as well as the first link up above explains the importance of length to spin, I would appreciate reading it.
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That's pretty much what my feelings have always been, too. I thought someone posted something on another thread here a while back about overstabilizing a bullet and losing accuracy.
I have seen lightly built bullets disappear before hitting the target. If you're shooting under the right weather conditions and stand behind the gun, you can see a vapor trail that ends in a puff of dust before it gets to the target. The two are independent phenomena, but it's really neat to see them both happen at the same time. We were trying for the puff of smoke effect and the vapor trail was a neat bonus.
I have seen lightly built bullets disappear before hitting the target. If you're shooting under the right weather conditions and stand behind the gun, you can see a vapor trail that ends in a puff of dust before it gets to the target. The two are independent phenomena, but it's really neat to see them both happen at the same time. We were trying for the puff of smoke effect and the vapor trail was a neat bonus.
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