Lazzeroni velocity?

[bwalker]

Can someone tell me how Lazzeroni advertises a velocity of 3,550 fps with a 160gr bullet out of 7.21 firebird when remington says the ultra mag can only muster 3,200 fps with a 160 gr bullet? Dont both have simular case capacities? Lazzeroni says a 27" barrel was used and remington says a 26 was used to obtain the advertsied velocities.

 

[Len Backus]

Meichele

I have heard the theory of faster velocities with slower twist barrels. I wonder if anyone has an informed opinion of how much difference this can make?

Let's start with a base muzzle velocity of 3400 with a 9 twist. How much slower would the higher pressures of an 8 twist barrel cause the velocity to be if loaded to the same pressure as in the 9 twist barrel?

 

[Michael Eichele]

Len,

I am not sure if you are dissagreeing w/my statments or wondering how much the differance is.

I need to go out and test how much the differance really is.

Quote:

Let's start with a base muzzle velocity of 3400 with a 9 twist. How much slower would the higher pressures of an 8 twist barrel cause the velocity to be if loaded to the same pressure as in the 9 twist barrel?

1st there is stated "higher pressures" then is quoted "the same pressure"

Is this a trick question???!!!

[ 12-27-2003: Message edited by: meichele ]

 

[Len Backus]

Meichele

No, no, I agree with you. I have always tried to use the slowest twist I could for a given bullet for this very reason.

What I meant to say was that if you use the same powder load you would get higher pressures in the faster twist barrel. But for safety reasons you would then decrease the powder load and end up with slower velocity.

How much slower is the question.

Clear as mud now?

 

[Michael Eichele]

bwalker,

Lazzeroni cases have much higher case capacities than the RUM cases. Think of them as being closer to the 378 case.

They also use slightly slower twists and longer barrels in their test guns. Slower twist will allow higher velocities w/less pressure.

Regards

 

[Michael Eichele]

LOL!!

Clear as mud!

Yeah, I really neeeeed to get out and test this.

 

[4mesh063]

Len, I would guess that the difference would be near impossible to see in testing. I have a brother who's a .223 nut. He's got a bunch of em. Anywhere from 7 twist barrels to 14 twist barrels. There's no discernable difference from one to the other and I don't know how much more spread there can be on the twist. If ever there should be a difference, here's the case. The same loads work in both twists also so I doubt there's a pressure variation either.

 

[Michael Eichele]

Quite possibly when the case size quadrupels there may be a differance.????

 

[Triple BB]

Reload your own. I shot a 165 grain Hornady Interbond at 3500 fps this past hunting season out of my 300 RUM. 3600 - 3700 fps is probably attainable with a 160 grain bullet. Your barrel may not last that long, but you'd be right up there with the Lazz...

 

[bwalker]

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>3600 - 3700 fps is probably attainable with a 160 grain bullet. <HR></BLOCKQUOTE>
I doubt it as the highest velocity loads I have seen put it about 3300 with a 160. This is with a 26" barrel.

 

[Michael Eichele]

Triple BB,

Dont forget that you were reloading for the 300 Ultra and the 7mm Ultra having a smaller bore, 26" for 26" he will not get velocities to equal the 300 even if the bullets weigh the same. If he increases the barrel in length he will then get blistering speeds, even w/160 grain bullet.

 

[Triple BB]

I didn't think he mentioned which caliber Ultra Mag he was talking about.

 

[MAX]

Just a guess on my part but I do not think a 1" twist change would have as much influence on pressure/velocity as the myriad other variables between different barrels/bores/chambers/brass etc. ad nauseum.

I'm sure it has an influence but don't have any idea at what point it would become quantifiable. The amount of energy expended to "spin" a bullet is very small.