6mm-223

[IceAxe]

For the 6x45 they are 20 and 24 inch. OBT seemed to be right on for my 7mm 08, factory ammo wouldn't group, then I tried the predicted OBT load and it was amazing. I have been reloading since the mid 70's but this OBT has really got me interested again. Just for grins I ran Buckshotbarlos's load through Quickload and look how close it is to node 4.

6mmx45-20in-75gVMax-8208.pdf

[buckshotbarlow]

ok, so now i'm gonna have to take the bait...nodes = harmonics?

Also, just looked up the info from hodgdon..weird:

[buckshotbarlow]

Just started working with Barrel Times ; what barrel length are you running?

http://www.shop.blackholeweaponry.co...15-6x45-20.htm
Following the options:

I was on midway tonight, looks like the stoner barrels might be coming back in stock...another build might be coming my way...

[eneranch]

I have the BHW 18" barrel in 6x45; was hoping for sub-MOA loads using 58gr to 75gr bullets, but have been unable to get repeatable results using OCW methods , am turning to OBT to further the cause.

[IceAxe]

ok, so now i'm gonna have to take the bait...nodes = harmonics?

Also, just looked up the info from hodgdon..weird:

The node is supposed to equate to a minimum disturbance at the crown. A harmonic dilation traveling down the barrel. Imagine a sine wave, the point at which the amplitude passes through 0 (normal) would be the node. Conversely, the point of highest amplitude (Crest or Trough) would be the anti-node. All these nodes are referenced or calculated by the speed of sound through steel.

[MarkCO]

The node is supposed to equate to a minimum disturbance at the crown. A harmonic dilation traveling down the barrel. Imagine a sine wave, the point at which the amplitude passes through 0 (normal) would be the node. Conversely, the point of highest amplitude (Crest or Trough) would be the anti-node. All these nodes are referenced or calculated by the speed of sound through steel.

That was one explanation of the theoretical, but many ballisticians who study the node theories have moved away from that. Controlling the parameters to that small of a margin are near impossible. There are actually load combinations that result in less total vibration/harmonics than others. There are some theories, but in general, it appears that specific load parameters combined with the chamber geometry, metallurgical occlusions (and other steel defects), barrel temperatures, etc. have a much more significant contribution to the crown having the same orientation w.r.t. POA than either the barrel oscillation or dilatation. The rail gun testing at White Sands produced a large amount of valuable data, but little has made it into the public realm. With the recent switch from magnetic pulse guns to laser as emerging technology, a lot of the traditional ballistics works that has been military funded has ceased. Doubtful we get any more ever.

[IceAxe]

[QUOTE=MarkCO;1795907]That was one explanation of the theoretical, but many ballisticians who study the node theories have moved away from that. Controlling the parameters to that small of a margin are near impossible. There are actually load combinations that result in less total vibration/harmonics than others. There are some theories, but in general, it appears that specific load parameters combined with the chamber geometry, metallurgical occlusions (and other steel defects), barrel temperatures, etc. have a much more significant contribution to the crown having the same orientation w.r.t. POA than either the barrel oscillation or dilatation. The rail gun testing at White Sands produced a large amount of valuable data, but little has made it into the public realm. With the recent switch from magnetic pulse guns to laser as emerging technology, a lot of the traditional ballistics works that has been military funded has ceased. Doubtful we get any more ever. [/QUOTE

You might be right, all I know is that I have had some consistent success with it.

[buckshotbarlow]

ok, kewl...thought that's what u meant with that pdf. I dug up my crap, and i'm going to load some .1 gr increments past 26 to 26.5 and see if i can hit it...

[IceAxe]

ok, kewl...thought that's what u meant with that pdf. I dug up my crap, and i'm going to load some .1 gr increments past 26 to 26.5 and see if i can hit it...

According to my calculations, without knowing you water/mass volume, you are already there.

[buckshotbarlow]

measured h2o in 5 cases...
32
31
31
30.6
30.7

average was 31.06gr
where in the table it was 31.65 gr. H2O


Ice, can u run the numbers?