Redneck with a 40
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Benchrest shooters have coined a phrase...."short and fat, is where its at".
.30-06 vs. .308 Win.: Long Range Choice?
- Thread starter Bart B.
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Zak, another thing about what happens when the rifle's not held exactly the same way for each shot.
Shooting the same rifle/ammo combination across 4 people in a long range match has often been done. Good idea when only one rifle is very accurate compared to the other three their owners have. I've noticed that every time I've coached a team doing this, every shooter has a different zero for the same conditions. They differed by up to one MOA; usually more in windage than elevation. With the slight differences between shooters in how they hold the rifle and their body's resistance to rifle movement during the bullet's barrel time, this is going to happen.
All the competitive high power rifle shooters I know who shoot well enough to sight in their rifle with only one or two shots from standing have noticed something else. While their windage zeros are within 1/4th MOA for standing, sitting and prone at all ranges, shooting off a bench requires up to a 2 MOA change in windage. When benched on sand bags, right handed shooter's rifles would shoot to the right, southpaw's rifles would shoot to the left. My .308's and 30 caliber magnums always shot about 1.5 MOA right from bags atop a bench compared to normal position shooting zeros. Proof that how one holds the rifle effects where it shoots relative to where it's aimed with a given sight setting.
Shooting the same rifle/ammo combination across 4 people in a long range match has often been done. Good idea when only one rifle is very accurate compared to the other three their owners have. I've noticed that every time I've coached a team doing this, every shooter has a different zero for the same conditions. They differed by up to one MOA; usually more in windage than elevation. With the slight differences between shooters in how they hold the rifle and their body's resistance to rifle movement during the bullet's barrel time, this is going to happen.
All the competitive high power rifle shooters I know who shoot well enough to sight in their rifle with only one or two shots from standing have noticed something else. While their windage zeros are within 1/4th MOA for standing, sitting and prone at all ranges, shooting off a bench requires up to a 2 MOA change in windage. When benched on sand bags, right handed shooter's rifles would shoot to the right, southpaw's rifles would shoot to the left. My .308's and 30 caliber magnums always shot about 1.5 MOA right from bags atop a bench compared to normal position shooting zeros. Proof that how one holds the rifle effects where it shoots relative to where it's aimed with a given sight setting.
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If one can get muzzle velocity spread from an '06 for 30 consecutive shots no greater than 20 fps, one may well shoot as accurate as a .308. This is the problem that plagued the '06 folks for so many years. Use your favorite ballistics software and see what a 10 fps change in muzzle velocity does for any bullet from either case in the vertical axis. The drop differences is around 4 inches for each 10 fps of change.
Two issues compounded this cause.
First, the '06's smaller shoulder diameter and lesser angle softened primer impact from the firing pin as it drove the case shoulder into the chamber shoulder. This happens to a greater extent than with the .308. In the '06, it caused a difference in primer ignition/detonation that caused different powder burn start up issues.
Second, the '06's longer powder column of the same diameter of the .308 is harder to burn as unifomly. Same reason benchresters like short, fat cases for best accuracy; more consistant powder burning.
To this end, if one can put 30 consecutive shots from a .30-06 in under 8 inches at 1000 yards, that's cause for my celebration and it's owner's pride. As far as I know, this ain't been done yet. It has been done with a .308.
Two issues compounded this cause.
First, the '06's smaller shoulder diameter and lesser angle softened primer impact from the firing pin as it drove the case shoulder into the chamber shoulder. This happens to a greater extent than with the .308. In the '06, it caused a difference in primer ignition/detonation that caused different powder burn start up issues.
Second, the '06's longer powder column of the same diameter of the .308 is harder to burn as unifomly. Same reason benchresters like short, fat cases for best accuracy; more consistant powder burning.
To this end, if one can put 30 consecutive shots from a .30-06 in under 8 inches at 1000 yards, that's cause for my celebration and it's owner's pride. As far as I know, this ain't been done yet. It has been done with a .308.
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USSR
Member
With the guys I normally shoot LR with, regardless of caliber, we are looking for ES numbers of <= 20, and SD numbers of <= 10 so as to minimize/eliminate stringing. This usually requires a bit of match prep work on the brass.
Don
Stew4570
Member
OK. I own a 30-06. I never played enough with the .308 to compare accuracy, but for the sake of this beaten to death topic I'm going to side with the .308. It seems that most of the 06 vs .308 matches were won with the .308.
I guess its one of those things you just accept. Like religion.
I guess its one of those things you just accept. Like religion.
Sunray
Member
"...the .30-06 was dumped years ago..." Because it ceased to be the military service cartridge.
The .308 proved to be more inherently accurate because of the ratio of case capacity to bullet diameter. There's a longish scientific explanation on-line somewhere. Forget where though. Something about short fat cases and the bullet diameter. It was also using new powders.
The .308 proved to be more inherently accurate because of the ratio of case capacity to bullet diameter. There's a longish scientific explanation on-line somewhere. Forget where though. Something about short fat cases and the bullet diameter. It was also using new powders.
USSR says:
I've never done any "match prep work" on brass. Lighter neck tension, mild primers and a full case of powder does well for me to get muzzle velocity SD's down around 5 to 7.
Try some RWS 5341 or PMC primers. The PMC ones don't deteriorate with age and they're extremely uniform.
I've never done any "match prep work" on brass. Lighter neck tension, mild primers and a full case of powder does well for me to get muzzle velocity SD's down around 5 to 7.
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They're equally accurate.
There's no such thing as an "inherently accurate cartridge".
I've had a long-standing offer in response to the old and tired argument of the .308 vs. .30-06.
Oddly, nobody's taken me up on it, even over the course of several years.
Here it is again:
Buy me the parts to build two identical target/precision rifles - one a .308 and the other a .30-06. I'll use Nesika Bay or Stolle long actions, and Krieger, Hart, Obermeyer, or Lilja barrels. They will be assembled to the latest benchrest standards, with the the same match-grade style of reamers, tight chamber dimensions, and so forth.
Assuming equal care and precision is used in handloading and matching the ammo to each rifle, the only difference in how they shoot will be determined by the person pulling the trigger. Period.
(The .30-06 will however demonstrate extra accuracy at ranges where the .308 will go subsonic and wobbly.)
There's no such thing as an "inherently accurate cartridge".
I've had a long-standing offer in response to the old and tired argument of the .308 vs. .30-06.
Oddly, nobody's taken me up on it, even over the course of several years.
Here it is again:
Buy me the parts to build two identical target/precision rifles - one a .308 and the other a .30-06. I'll use Nesika Bay or Stolle long actions, and Krieger, Hart, Obermeyer, or Lilja barrels. They will be assembled to the latest benchrest standards, with the the same match-grade style of reamers, tight chamber dimensions, and so forth.
Assuming equal care and precision is used in handloading and matching the ammo to each rifle, the only difference in how they shoot will be determined by the person pulling the trigger. Period.
(The .30-06 will however demonstrate extra accuracy at ranges where the .308 will go subsonic and wobbly.)
Gewehr98 says:
Well, maybe cases were better back then. Find a batch of .30-06 Western Cartridge Company white box match ammo, strip it down, then measure the cases for uniformity.
By the way, the most accurate rifles I know of do not use tight chamber dimensions; just standard SAAMI ones.
Folks did exactly that back in the '60's. They used actions and barrels equal to what's available today. A couple even used the same rifle and changed only the barrel to eliminate as many variables as possible. Maybe the powders were different, possibly the primers, but barrels, cases are the same. No action's shot better groups that what the Win. Mod. 70's done; maybe one or two have come close. Anybody ever used a Nesika Bay or Stolle long action or even a BAT to put several consecutive 10-shot groups at 600 yards all under 1.5 inches?
Well, maybe cases were better back then. Find a batch of .30-06 Western Cartridge Company white box match ammo, strip it down, then measure the cases for uniformity.
By the way, the most accurate rifles I know of do not use tight chamber dimensions; just standard SAAMI ones.
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USSR
Member
RWS primers have always been virtually unavailable. Regarding the PMC primers, here is the story. For several years in the early 2000's, there was a guy in Arizona (the name escapes me) who imported primers directly from a Russian primer factory. The word soon got out that the ES and SD numbers of these Russian primers were incredibly low, and all the LR shooters wanted them. David Tubbs thought so highly of them that he bought 700,000 of them. I bought 5,000 of them myself. The large rifle primers were labeled as KVB-7. At some point (about 2005), the Russian primer manufacturer stopped selling them to the guy in Arizona, and contracted with PMC to supply their primers under the PMC name. This arrangement only lasted about a year or two, and then the Russian primer manufacturer contracted with Wolf to supply primers under the Wolf brand name, where it remains to this day. So, if you want these quality primers, you need to buy Wolf primers.
Don
USSR says:
The Old Western Scrounger in the north San Francisco Bay area used to carry RWS primers but they're no longer listed on his web site.
Thanks for the update. I was about ready to call Bob Jones in Arizona and ask if he had some of those PMC primers. Now I'll ask for Wolf.
The Old Western Scrounger in the north San Francisco Bay area used to carry RWS primers but they're no longer listed on his web site.
USSR
Member
Bart, that's the guy who used to sell the Russian primers.
Don
Sport45
Member
What impact would the length of the bolt have on accuracy? I know the locking lugs are up front, but it seems the shorter bolt of the .308 may be a little bit stiffer and would vibrate less.
Sport 45, I don't think the bolt's stiffness is important to accuracy. As long as it locks up in the same orientation relative to the receiver and cartridge each time, that's all that counts. Accuracy is repeatability. How much stuff moves around for each shot ain't important. It only has to move the same speed, amount and direction each time.
Even barrel stiffness is not a big thing. If it was, then Palma rifles with their long, thin, whippy barrels would not shoot just as accurate as a thick, short, heavy, stiff one.
Which reminds me that many folks want a fluted barrel 'cause they think it makes 'em stiffer. Well, what's stiffer, a wood deck made with only 2x6's stacked on edge then glued together or made with alternating 2x6's and 2x4's glued together? Same thing as removing metal strips around the barrel. You've removed material that made the plain one as stiff as it is. Guess which one is stiffer now?
Even barrel stiffness is not a big thing. If it was, then Palma rifles with their long, thin, whippy barrels would not shoot just as accurate as a thick, short, heavy, stiff one.
Which reminds me that many folks want a fluted barrel 'cause they think it makes 'em stiffer. Well, what's stiffer, a wood deck made with only 2x6's stacked on edge then glued together or made with alternating 2x6's and 2x4's glued together? Same thing as removing metal strips around the barrel. You've removed material that made the plain one as stiff as it is. Guess which one is stiffer now?
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Common misconception.
From an engineering standpoint, a fluted barrel is stiffer than a comparable barrel turned to the minor diameter of the fluted barrel, but not quite as stiff as a comparable barrel turned to the major diameter of that same fluted barrel. You can't have your cake and eat it, but there is a compromise.
That doesn't mean you can't get a pencil-thin or sporter-weight screamer of a barrel from Krieger, Obermeyer, Hart, Lilja, Mike Rock, etc. You'll still be working with barrel harmonics on such a whippy thing, but it can be done. Just like I can build a .30-06 that's every bit as accurate as a .308, if not more so.
From an engineering standpoint, a fluted barrel is stiffer than a comparable barrel turned to the minor diameter of the fluted barrel, but not quite as stiff as a comparable barrel turned to the major diameter of that same fluted barrel. You can't have your cake and eat it, but there is a compromise.
That doesn't mean you can't get a pencil-thin or sporter-weight screamer of a barrel from Krieger, Obermeyer, Hart, Lilja, Mike Rock, etc. You'll still be working with barrel harmonics on such a whippy thing, but it can be done. Just like I can build a .30-06 that's every bit as accurate as a .308, if not more so.
USSR
Member
+1. The common misconception is that by fluting a particular barrel, it makes it stiffer than if you didn't flute it. Actually, the comparison is made between a same length barrel with a slightly smaller contour of the same weight as the newly fluted barrel; it's stiffness by weight comparison.
Don
The contour, material and dimensions of the barrel are the important parameters in terms of stiffness. When I ordered my two Krieger barrels I chose the MTU contour to provide maximum stiffness with minimal weight. I ran this comparison a few months ago using SolidWorks for three different barrel contours all made from 304 stainless, all with a .308" bore and all 26" long. The "MAX" value at the end of each barrel is the maximum deflection in inches due to the weight of the barrel alone. I never got around to putting flutes in the barrels and running those models but I'd like to do it for my own interest.
As for flutes, they're attractive (to me) and in my case, reduced the weight of the barrel by 1/2 lb ... at the cost of a minimal reduction in stiffness (and I'll prove it eventually). As for heat transfer, they probably improve radiation and convection cooling by a minimal amount (maybe not enough to matter) ... but they sure look good!
1858, your comments on stiffness reduction and cooling are right on. When I was working, a mechanical engineer used his software to compute rigidity in barrels with different flute depth, width and number of flutes. Never got more than a 10 percent change.
Heat dissapation was less noticable. Only about 7 percent more heat dissipation happened with fluted barrels.
I asked another mechanical engineer in Arizona about a formula to calculate the base, or fundamental frequency a barrel had for different contours and calibers. He made me one that calculates very accurate what frequency barrels vibrate at. Most of 'em are about 50 to 60 cycles per second. There are higher harmonics but the greatest amount of muzzle vibration is at this low frequency. You (or anyone else reading this) can buy this software from his web site at:
http://www.vibrationdata.com/StructuralFE.htm
The software and its information sheet are:
rifle_frequency.exe rifle.pdf
Or, send me your e-mail address then I'll send you an attached copy of it absolutely free.
It shows easily what barrel countours are stiffer as the higher their resonant frequency, the stiffer they are.
Heat dissapation was less noticable. Only about 7 percent more heat dissipation happened with fluted barrels.
I asked another mechanical engineer in Arizona about a formula to calculate the base, or fundamental frequency a barrel had for different contours and calibers. He made me one that calculates very accurate what frequency barrels vibrate at. Most of 'em are about 50 to 60 cycles per second. There are higher harmonics but the greatest amount of muzzle vibration is at this low frequency. You (or anyone else reading this) can buy this software from his web site at:
http://www.vibrationdata.com/StructuralFE.htm
The software and its information sheet are:
rifle_frequency.exe rifle.pdf
Or, send me your e-mail address then I'll send you an attached copy of it absolutely free.
It shows easily what barrel countours are stiffer as the higher their resonant frequency, the stiffer they are.
Zak Smith
Member
1858,
I would be interested to see the same data for the Palma contours or the Tubb profile.
-z
I would be interested to see the same data for the Palma contours or the Tubb profile.
-z
Bart B. said:
I'd be interested to hear your thoughts on how the barrel vibrates, particularly the path that the muzzle takes during one complete cycle. Varmint Al has some interesting information HERE but as far as I can tell, all of the barrel vibration that he refers to is up/down. Based on my experiences during load development, I'm sure that the muzzle/barrel vibrates by rotating around a center with increasing/decreasing radii (during one cycle) and not merely up/down.
Zak Smith said:
Zak, Krieger lists three Palma contours, light, standard and heavy but I can't find any data on the Tubb profile. Do you have some dimensions?
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Zak Smith
Member
I don't, sorry.
1858 wants to know.....
When fired, the recoil force axis is in line with the bore. The bore's usually above the butt plate center and that means the force will move the barreled action, or the reciever axis up. Moving the receiver axis up causes the muzzle axis to point down at first as the barrel bends down, then it swing upwards towards the top of its first whip cycle. Varmint Al's web site has excellent animated graphics showing this.
Somewhere in that upward swing is where the bullet will leave. Faster bullets will leave sooner in that upward swing and slower ones will leave later. With the typical muzzle velocity spreads high power rifles have, the difference is insignificant.
If one has a cartridge with a big spread in muzzle velocity, long range accuracy will be improved because of this anomoly. The slower bullets leave much later in the first upward swing compensating for their more arched trajectory making that bullet strike higher than normal. Bullets at the higher end of the velocity range will leave sooner and that's fine as they will shoot flatter.
Such compensation is why the British SMLE rifles loaded with Cordite producing huge muzzle velocity spreads were favored by the Commonwealth folks for long range matches. The rear locking SMLE action added to this compensation. Accuracy was not very good until at least 500 yards and got better up through 1000. They performed wondrous feats of accuracy with the .303 British and were often world champions in international Palma matches. The Brits liked front locking Mauser 98 actions for short range matches as they shot more accurate there with Cordite charged cases. US military tests with M14 rifles show a small amount of compensation with M118/M852 match ammo due to the gas port being about mid point in the barrel. Their theory is as gas escapes, that jet action bows the barrel up at its middle pointing the muzzle axis lower for higher pressure/velocity and higher for lower pressure/velocity instances.
As far as I'm concerned, it's a myth that bullets have to leave at the top or bottom of the barrel's whip cycle. If the barrel whips/vibrates at only 50 Hz, it goes through one major cycle in 20 milliseconds. It only points down for a small fraction of a cycle when fired then then back up to its highest angle about 15 milliseconds after its fired. Bullets leaving at 3000 fps have a barrel time of about 1 millisecond and typically leave on the first upward swing exiting before the muzzle's pointing at its greatest angle.
There's not much barrel whip horizontally. Creighton Audette demonstrated some years ago that rounds with unsquare case heads striking the bolt face at one side caused horizontal shot stringing. Out of square case heads contacting the bolt face at its top and bottom had a much smaller effect due to that point being in line with the bolt's recoil lugs. He would alternate the high point left and right on the closed bolt face and there would be two groups; each one centered equidistant sideways from the aiming point. That's proof that some horizontal whipping can happen, but not with proper bolt faces and case heads.
I and others have shot several rounds of .308 Win. through chronographs at 1000 yards noting where the bullets struck relative to where the shot was called. We all got data that faster bullets struck higher than slower ones by an amount virtually equal to what ballistic software predicted. Evidence that they all left at virtually the same place in the barrel's whip cycle and no compensation occured.
Until someone puts near weighless accelerometers on barrels (or reflects laser beams off barrels into photo cells) to accurately measure actual movement at all frequencies, all we can do is scientifically guess where the muzzle will point when the bullet leaves. I saw many years ago some spark photographs made decades earlier showing bullets leaving M1903 barrels on their upward swing but don't rember any good stuff that was written about it.
Well, high power rifle bullets are long gone before the barrel vibrates, or whips, through one cycle.
When fired, the recoil force axis is in line with the bore. The bore's usually above the butt plate center and that means the force will move the barreled action, or the reciever axis up. Moving the receiver axis up causes the muzzle axis to point down at first as the barrel bends down, then it swing upwards towards the top of its first whip cycle. Varmint Al's web site has excellent animated graphics showing this.
Somewhere in that upward swing is where the bullet will leave. Faster bullets will leave sooner in that upward swing and slower ones will leave later. With the typical muzzle velocity spreads high power rifles have, the difference is insignificant.
If one has a cartridge with a big spread in muzzle velocity, long range accuracy will be improved because of this anomoly. The slower bullets leave much later in the first upward swing compensating for their more arched trajectory making that bullet strike higher than normal. Bullets at the higher end of the velocity range will leave sooner and that's fine as they will shoot flatter.
Such compensation is why the British SMLE rifles loaded with Cordite producing huge muzzle velocity spreads were favored by the Commonwealth folks for long range matches. The rear locking SMLE action added to this compensation. Accuracy was not very good until at least 500 yards and got better up through 1000. They performed wondrous feats of accuracy with the .303 British and were often world champions in international Palma matches. The Brits liked front locking Mauser 98 actions for short range matches as they shot more accurate there with Cordite charged cases. US military tests with M14 rifles show a small amount of compensation with M118/M852 match ammo due to the gas port being about mid point in the barrel. Their theory is as gas escapes, that jet action bows the barrel up at its middle pointing the muzzle axis lower for higher pressure/velocity and higher for lower pressure/velocity instances.
As far as I'm concerned, it's a myth that bullets have to leave at the top or bottom of the barrel's whip cycle. If the barrel whips/vibrates at only 50 Hz, it goes through one major cycle in 20 milliseconds. It only points down for a small fraction of a cycle when fired then then back up to its highest angle about 15 milliseconds after its fired. Bullets leaving at 3000 fps have a barrel time of about 1 millisecond and typically leave on the first upward swing exiting before the muzzle's pointing at its greatest angle.
There's not much barrel whip horizontally. Creighton Audette demonstrated some years ago that rounds with unsquare case heads striking the bolt face at one side caused horizontal shot stringing. Out of square case heads contacting the bolt face at its top and bottom had a much smaller effect due to that point being in line with the bolt's recoil lugs. He would alternate the high point left and right on the closed bolt face and there would be two groups; each one centered equidistant sideways from the aiming point. That's proof that some horizontal whipping can happen, but not with proper bolt faces and case heads.
I and others have shot several rounds of .308 Win. through chronographs at 1000 yards noting where the bullets struck relative to where the shot was called. We all got data that faster bullets struck higher than slower ones by an amount virtually equal to what ballistic software predicted. Evidence that they all left at virtually the same place in the barrel's whip cycle and no compensation occured.
Until someone puts near weighless accelerometers on barrels (or reflects laser beams off barrels into photo cells) to accurately measure actual movement at all frequencies, all we can do is scientifically guess where the muzzle will point when the bullet leaves. I saw many years ago some spark photographs made decades earlier showing bullets leaving M1903 barrels on their upward swing but don't rember any good stuff that was written about it.
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Bart B. said:
This is something that is open to a certain amount of debate without the means to empirically determine the time it takes for the bullet to exit the muzzle after the firing pin strikes the primer. Varmint Al states "The approximate time that it takes a 3300 fps muzzle velocity bullet to exit the barrel, assuming a constant acceleration, is 0.0011 seconds. Actual exit times would be longer since the bullet is not under constant acceleration and the time from the firing pin first hitting the primer, ignition starts, is not included." So for a .308 Win with a muzzle velocity of 2700 fps, still subject to the same limitations, what is the ACTUAL time in the barrel?
Zak, here are some deflection results (inches) for the Palma contour (heavy, standard and light) with the dimensions given by Krieger HERE. Since their Palma contour has a 30" barrel, I calculated the O.D. of the muzzle assuming that the barrel was cut off at 26" for comparison with the MTU contour above.
Zak Smith
Member
That is some of the most interesting data I've seen posted on THR, thanks.
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