If I wanted to measure the oscillation rate of a barrel (at any point or interval) as it is discharging, what equipment would I use?

If money is no object, then use eddy current proximenty probes set up in a similar way as used for shaft monitoring in high speed turbines and other rotating equipment. Output can be fed into a computer, and with the correct software you can see everything and make neat graphs. The Bently Nevada corporation will be glad to build a system for you.

A method like this would sure make load development easy, and would tell you just where to cut that barrel so the bullet exits at a node.

John--

Right on. They'll build it if your check is heavy enough....

But, didn't you mean to say, "cut at the half node"?
AT the node the barrel can be pointed in any direction because at *that* point the barrel is not moving, but the space of barrel between the nodes are. So, to get the barrel pointed at the same place every time the bullet must exit between the nodes AND the barrel deflected in the same direction every time........of course the nodes change as you cut the barrel and also aren't evenly spaced because of the taper of the barrel affects vibration at different points..... There's also considerable debate about where the barrel should be cut in relation to the node...

It SURE gets complicated in a hurry.

Alex--- I'd suggest sending the barrel to a company that graphs the twist rate consistentcy and crown the barrel at the very end of a good smooth section.

You can determine the location of the nodes by magnetizing the barrel and spreading iron filings on it before shooting. You'll see the node(s) after about 5 shots. They aren't well defined because every shot is slightly different and that spreads the node(s) out over an inch or two.

I have no idea. I do know how to find the harmonic nodes.......for free!

Hang the barreled action horizontally with string. Hang several u-shaped loops of wire on the barrel. Tap the barrel to make it ring. Watch the loops migrate to the "quiet" spots where the barrel oscillates the least. There will be several.

If there is a reasonably located quiet spot near the forend tip, that is where I put the tip pressure, if I want tip pressure. Seems logical since it should whip the barrel away from the stock least. I have not played with moving the pressure point fore and aft so I can't be sure.

Scot---

Change the material of the hammer you use and you'll see the nodes change places on the barrel. The question is where are the nodes with a copper and lead "hammer".

I worked on this problem for a year in the early '70s using every test I could devise on two identical 40XBBR 6x47s.

You can get pretty close with the U wires, but a better way is to build and install a moveable bedding fixture in the forend. Make it adjustable for tension on the barrel and the position of that tension along the barrel.

It's amazing to watch the group change POI by moving the bedding buttons a quarter of an inch fore and aft. I found that if you make the point of contact and inch long it no longer makes any difference where it is. It just works.

Most centerfire barrels I've messed with have two nodes. One about 7 inches ahead of the receiver ring and one about 14.......one third and two thirds the length of the barrel ahead of the receiver.

The REAL secret is making the whole gun straight, square, and solid so the vibration of the barrel is not as violent....then the nodes make less difference.

Back when I was a rotating equipment engineer for one of the major oil companies we pioneered some of Don Bently's stuff working with him. An incredibly brilliant man and quite a character. These days I suspect you are in for around $5-10M or so for a power supply, a 2 channel monitor, and proximity probes. Of course you can use an oscilloscope with the probes, not sure what scopes go for these days. Then you will need to build a fixture to hold the rifle and probes (I am sure Jack would fix you up well here...). In summary, major bucks.