Nodal Tune

[!Peter!]

Hi All,
I've been digging through all of the great technical info on this site and one thing that I can't quiet work out is what is ment by a nodal tune. Could someone give some more information on a nodal tune?

I understand the purdy PX, OBT/ OCW, ladder and Varmit Al's analysis but I haven't found enough information to understand what a nodal tune is.

Also thanks to everyone for a great forum, there is a lot of great information and great discussion!

Peter

[DenisA]

A nodal tune is the simplest type of tune. The one that the majority of shooters develop by load testing in incremental powder charges.

When cartridge ignition begins, harmonics occur through the barrel. As the muzzle oscillates, the timing of bullet exit is controlled by bullet speed which is powder charge. You have peaks (top of the oscillation), troughs (bottom of the oscillation) and in-between the peak and trough which is an area that doesn't yield consistency because the muzzle is travelling too quickly in a given direction.

Take a peak for example. As the muzzle is moving up quickly and decelerates to change direction, the muzzle is in its most consistent position for the longest period of time before it moves back down and starts to accelerate too quickly to be useful. That consistent area at the peak is a node.

Different barrels, powders, bullets, etc, have different length nodes. A typical length I have found with a bare barrel (no weights) is .4gn of powder long. I have had some that were much longer. Choosing the middle of the node as your load means that you should be at your tightest tune and have leeway either side of that to allow for some environmental (ambient temperature) changes and such.

Being in the middle of a peak or a trough is a nodal tune.

[plumbs7]

Hi Pete, I'm not that qualified to comment ; Williada would be the barrel whisper on this .
However, nodal tune is a range in fps that the OCW , lowest extreme spread and harmonic barrel timing to produce an accurate tune . However, what works at 300 yds may not necessarily work at a 1000yds .

As we saw an et sheet of Mat p's shoot at 500 yds I think it was ? ( sorry Mat for using that example!).With the load having a high sd produced a good score and the low sd load was way out of barrel timing and large vertical. Seat depth or increasing or lowering the charge may have helped. I would suspect the high sd load even though it hummed at 500 and maybe even 600 yds . But at 1000 would have been most likely from 5 ring to 5 ring.

You could say that even though he had low sd , it was out of nodal tune ! This is where , tuners or dampeners and o rings have come to the rescue! In trying to tame the vibrations and extend the node . Thus , hopefully extending the vibrations node and make tuning more user friendly.
Also hopefully slightly positive compensating .

My Sensai will hopefully add to the above lol! (Williada).

Also what Denis said ! Like button !

[DenisA]

However, nodal tune is a range in fps that the OCW , lowest extreme spread and harmonic barrel timing to produce an accurate tune .

To my understanding, I don't think a nodal tune represents the lowest ES. This is one reason why tuners can be beneficial. The lowest ES maybe at either extreme of a node and tuner can be adjusted to utilise the low ES powder charge and bring the node centre up or down to work together.

[johnk]

How I've been doing it for match rifle since 2002.

[!Peter!]

Thanks for the responses, DenisA post explains it for me.