1:7 vs 1:8

[darkker]

1) The hunting line is what most of the Long-range Benchrest shooters use in there 600/1000 yard chamberings because the jackets are more concentric.
2) If you are a Competitive Shooter you only switch to the target bullets if you are experiencing failures.
3) Friction is what caused the failures not rotational forces.
4) Bullet length all else the same determines twist rate not velocity.
5) If your gyroscopic stability is 1.5 it doesn't matter what velocity your shooting because a 1.5 GS means the bullet is stable.

6) The only time twist rate comes into play is guys with a GS of 1.2 shooting 1000 yards and maximum loads in a very long barreled 308..

This is absolute lunacy.
1) Maybe they do use them, but it IS NOT because of jacket uniformity. They would use them because of jacket damage in high heat, rapid fire situations Call Berger and ask them that, or better yet read that it isn't true in their FAQ.
http://www.bergerbullets.com/information/faq-frequently-asked-questions/
None of this has anything to do with your false claims of G forces by the way.
2) That is also not true, but the WHY they would switch is perfectly reasonable. Again this is a deflection from your G force claims, and if they were killed by G forces, they wouldn't stay with these bullets as you claim. So which is it? You can't have both sides of the argument.
3) Friction is what damages the jacket, on that we both have always agreed. Once that bullet is out of the barrel, is where, in an attempt to keep this nonsense relative to the OP, in a high RPM situation, will then destroy the bullet. NOT the G forces.
4) I'm not sure what this is supposed to mean. I agree that bullet length is what you should consider to choose a twist rate. HOWEVER, ignoring velocity simply shows you don't understand what you are talking about. So here is your formula, AGAIN: MV * 720 / Twist = RPM.
5) Again, Velocity is CRITICAL to your stability factor, as it DIRECTLY affects the RPM. The RPM is in fact what gives you stability. Look at the formula, again, and do the math. MV = Muzzle Velocity. Without a velocity, there is zero RPM. Only a useless twist rate, and a cartridge in a chamber that you can't fire.
6) Again false. Why did the original 6mm Remington Fail? Because it had a slow twist to ensure that no varmint bullets would be destroyed. Thus it could not handle anything heavy enough to hunt game with, where the 243 had a twist that generally worked with several bullets.
Or more recently look at the 223 WSSM cartridge. If your claim of velocity not mattering or G forces caused the damage, then they would have used a 9-twist. Why didn't they? Because the velocity possible in that cartridge would impose an RPM that would destroy anything remotely useful for varmint hunting.

[Lynn]

I don't want to burst your bubble but the bullets are actually damaged in the barrel and generally blow up within 60-80 yards downrange or fail to reach the target as Eric Stecker likes to put it.
As to the lunacy I won the 2010 NBRSA 1000 Yard Benchrest Nationals with that lunacy and jacket concentricity is indeed better with the thinner jackets period. They are harder to make but better.
And Eric knows me so don't take my word on it give him a call I already know what he will tell you.

As to your twist rate ?please read my post again.
It should read that if your gyroscopic stability is 1.5 the velocity doesn't matter.
If your shooting a 6BR at 2850 fps AND the twist rate gives you a GS of 1.5 you are good to go.
If your shooting a 6mm-06 Ackley Improved at 3500 fps AND the twist rate gives you a GS of 1.5 you are good to go.
That is what I actually said.
What I didn't say was to shoot 55 grain bullets out of a 7 twist barrel at maximum velocity in a 6mm-06 Ackley Improved as the GS would be too high.

[Lynn]

http://bulletin.accurateshooter.com/2010/05/berger-bullets-releases-new-338-hybrid-dual-ogive-bullet/

If you look at the numbers in the enclosed link you will find the BC number to be 0.950 not 0.818 or 0.822 like it is on the boxes of today.
The reason for the huge variation was due to "ogive slumping" and Eric or Bryan can explain its causes to you or you can search it on Google where it is also clearly explained.
Good Luck with your future shooting.
Lynn

[LoneWolf]

Lynn beware.... arguing with Darker is futile.

[Lynn]

I am not arguing here with anyone as it wastes time. I am here to share and to get some answers.
I just looked up the earlier post.
Here are a few interesting facts about, say a
30 cal. 1000 yard load that shoots a bullet having a maximum acceleration
that makes the acceleration of a fuel dragster pale by an order of many
magnitudes:



First let me give you the true definition of
acceleration, "a": a = dv/dt, where dv in an infestimally small change in
veloctiy and dt is an infestimally small change in time corresponding to
the change in velocity and occurs at a point in time. I
realize that is not too colorful but you can use that equation to estimate the
average acceleration of a fuel dragster. That is a = (333
mph*88f/s/60 mph)/4.441 sec = 109.97 f/sec2 or 109.97 ft/sec2/32.17405 ft/sec2
= 3.41 g's. Acceleration defined in words is the rate of change in
velocity with respect to the accompanying change in time.



Now for the 30 cal mag. load shooting a 220 grain
MK at a muzzle velocity of 3002 f/s with a barrel time of 0.001711
seconds:



The average bullet acceleration in the
barrel is 54,532 g's (That is the fuel dragester's average
acceleration increased by a multiple of 15,991 times.)

The maximum acceleration, which occurs near max.
chamber pressure, is 126,849 g's (Under that amount of acceleration, a
free standing column of pure lead taller than 0.077" will began to collapse upon
itself.)

Power is the rate that energy is transmitted.
One Horsepower is defined as delivering or transmitting 550 ft-lbf in one
second. Thus one can calculate the average rate that energy is delivered
to the 220 grain VLD thus:



(3002)^2*220/450436.7/0.001711sec/(550
ft-lbf/sec/HP) = 4677 Horspower That is a lot of Horsepower for
such a small bore but true, although the delivery time is very short for
the single stroke rifle "engine" and the peak Horsepower would likely
be much higher but I would have to modify my internal ballistics program to
estimate the peak HP. Peak energy delivery rate to the bullet, or
peak HP, would likely occur well past maximum chamber pressure.



If the 300 Mag. were fired, such that the bullet
was exiting the cartridge case and entering the barrel bore as the
fule dragster was about 80 yards from the finish line, the bullet would reach
the finish line first.

If the math is correct I was in error earlier by 11 G's

[foxx]

Futile, but amusing. :)

[FW Conch]

^ +1 ^ ;-))

[sharpshooter]

Back to the original question......if the top shooters are setting the world on fire with 103-108 gr bullets, why would you want to shoot a 115? I don't know of anybody shooting them with the same success as the lighter ones.

[darkker]

1 -I am not arguing here with anyone as it wastes time. I am here to share and to get some answers.

2 -30 cal. 1000 yard load that shoots a bullet having a maximum acceleration
that makes the acceleration of a fuel dragster pale by an order of many
magnitudes:

3 -Now for the 30 cal mag. load shooting a 220 grain
MK at a muzzle velocity of 3002 f/s with a barrel time of 0.001711
seconds:

4 -The average bullet acceleration in the
barrel is 54,532 g's (That is the fuel dragester's average
acceleration increased by a multiple of 15,991 times.)

5 -The maximum acceleration, which occurs near max.
chamber pressure, is 126,849 g's (Under that amount of acceleration, a
free standing column of pure lead taller than 0.077" will began to collapse upon
itself.)

6 -(3002)^2*220/450436.7/0.001711sec/(550
ft-lbf/sec/HP) = 4677 Horspower


1 - I agree. This is about info. I believe the info keeps getting confused, and is incorrect.
2 - Yes, bullets are much faster than a Top Fueler, but we aren't discussing cars. Nor are we discussing a heavy 30-cal bullet.
3 - Again, Not discussing those bullets, or twists. You need to stick to the topic, and associated numbers relevant to it. 115gr 6mm bullet.
Your math seems sound from a purely mathmatical standpoint, just not practical. You are assuming absolutes that aren't actual. There is a significant loss in the form of heat transfer to the barrel. There is loss due to the case being expanded and cooling the powder, there is gas bypass when the bullet engraves in the lands, there is gas bypass because the bullet isn't a true 100% seal while traveling in the barrel. Not all powders have the same burning rate, the same burning curve, nor burn the same at different pressure levels. I also question your barrel times. Here are a few different pressure traces that we have done in the Creedmoor. They are the closest thing I have to the 6mm. None the less will all of my 30-cal work the fundamental premise holds true.

http://i78.photobucket.com/albums/j84/Darkker13/Mobile%20Uploads/Screenshot_2015-01-11-14-00-36_zpsrz6rkepr.png
http://i78.photobucket.com/albums/j84/Darkker13/Mobile%20Uploads/Screenshot_2015-11-26-20-22-08_zps0aeacd6x.png
http://i78.photobucket.com/albums/j84/Darkker13/Mobile%20Uploads/Screenshot_2014-12-26-20-33-14_zpskz7cqnti.png

5 - I can't speak on what a colume of lead will endure. But again the topic is whether or not the damage to the jacket allow the Centripetal force to overcome it's yield strength is the issue.
6 - Fine. The debate isn't whether or not a horsepower number is or is not being generated; you keep side stepping your original arguement with herrings. The whole question is whether or not a damaged jacket will have centripetal force rip it apart. Back to my previous post, under question #6. IF the RPM had nothing to do with bullet destruction, then why are none of the factory high speed cartridges of the world using ultra fast twist barrels; such as we are discussing? Because the RPM WILL rip them apart.
If the jacket damage is soley due to collapsing/melting lead, and the RPM has nothing to do with ultimate bullet destruction; Then there would be zero reason to not have fast twists in everything. The acceleration is the same regardless of twist, and as you contend if the RPM doesn't destroy the bullets; no reason to not use them.
As I have said several times, Barrel smoothness plays a large role in jacket damage and thus what RPM the bullet can withstand. This isn't a hard-and-fast number. So bullets don't simply explode or not at a given RPM.

[FW Conch]

Let's hear what "scope" has to say. He knows how to "particalize" dem pills ! :-)

[jsthntn247]

I shoot a 1:7 criterion with dtacs in my 243. Works great, just make sure the reamer has no longer than .090 freebore if you want magazine feed.

[Lynn]

Darker
As you just posted the jackets get "Ripped" in the barrel then fail after they exit.
So it is not the rotational force that is destroying them but the rip as you put it that takes place in a rough or very long barrel due to friction.

[Lynn]

This is a good question.
Not all competitions are about shooting the smallest possible groups. Some competitions have a 10 inch Bullseye and most bullets with a bc number above 0.500 will get the job done. That is a GENERALIZATION!!!!!
In Benchrest were only the smallest groups count accuracy trumps all else while in other disciplines hitting nearer the center of the target plays the more prominent role.
In a large case like a 6-284 or a 6mm-06 the top accuracy node is roughly 3425 fps with a lighter bullet and 3200 fps with the 115.
That 225 fps difference can be put into a ballistic program and it will show you which bullet to use if they both shoot the same sized groups at 100 yards.
If they are both equally accurate you pick the ballistic winner.
Now if your score determines the winner and not the group the 115's will handle the wind better so that would be your bullet.
In shooting you test everything and make your choice based on the results not emotion or sentiment.

[Lynn]

Darker
You had some specific questions in your earlier posts and that is why I posted the results.
You claimed the acceleration was wrong and as it turns out I was off by 11 G's out of 127,000 so I just rounded it off. I included it only in the case I had made a math error.
I am not familiar with your trace analysis as I use a Oehler 43 with strain gages and acoustic targets for my testing. They cost a bit more but you learn alot so a happy trade off.
On the barrel time I used a 30 inch competition barrel 1.450 inches straight cylinder.
I see you were using a very thin profile and 24 inches long. I will assume a hunting rifle?
Lynn

[Captain Obvious]

Don't mind dakkar, he means well but he's pretty opinionated and not very open-minded to the possibility that he doesn't know everything.