Comparing Quick Load Data

[RW]

A question on comparing Quick Load data, What would you look for in a powder and charge weight That is close to 100% Load that has the Filling/charge weight
that are close to 100% load density? And look for powders that fill to around 100% with the most MV?
I know that you would like a charge to be somewhere around the the 100% load density but some powders might not be at a 100% and still perform well! Looking for accuracy but it would be nice to have the most velocity. And I don't like to have compressed loads as I have trouble with seating depth. Then there is the single base vrs double base issue to consider. I do know that in the end you have to try them all, but I was wondering what other people use when considering powder and load from quick load? Thank You, Ron

 

[CharlieNC]

Look up Optimal Barrel Time (OBT) by Chris Long; based on barrel length it provides a table where nodes occur as measured by the barrel time. Then you can use QL to find loads which give the calculated OBT nodes across a range of charges, which also are safe pressure. Do a ladder test across the charge weight range (two shots per charge should be adequate) that covers both the low and high velocity nodes to map out your exact barrel harmonics. While the target node may not exactly match the OBT prediction, you will find one or two nice nodes where the effect of charge on vertical POI is minimal. There is a lot published on this topic that you can google for as much detail as you want.

 

[mikecr]

I work with the fastest powder that fills the given H20 capacity(as fire formed), at QL listed max pressure.

 

[Bart B.]

Look up Optimal Barrel Time (OBT) by Chris Long; based on barrel length it provides a table where nodes occur as measured by the barrel time.

I have little faith of Quickload's worthiness if based on OBT theory. The speed of sound in barrels it states is not what mechanical engineering sites list for barrel steels.

And squeezing barrel muzzles down reducing inside diameters a couple or few ten thousandths inch doesn't change accuracy any significant amount. Nor does belling it out that much or more.

OBT site says

the basic resonant (beam bending or “ruler on the edge of the desk”) mode of a cantilevered barrel (beam) made of steel at our typical lengths and diameters is on the order of 500 to 1000 Hz

Mechanical engineering software calculates them to be about 40 to 100 Hz (cycles per second.

Al Harrel's barrel harmonic article has the muzzle diameter changing a fraction of what OBT claims. Note the barrel's mode 1 resonant frequency as well as others:

http://www.varmintal.com/amode.htm

Quickload's rep said user's results show trends in component and barrel changes but don't expect customer's results to match theirs. Their components are not exactly the same as what customers use. But it's a good place to start.

 

[riflewoman]

I can’t remember exactly, but when I was in engineering school a couple of us on the rifle team did a shaker test of a Winchester M52D barreled action. The first node was somewhere around 200-400 hertz and was very loud. We deduced that rifle barrel vibrations were very complex indeed.

 

[Bart B.]

Good vibrations. ....

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

 

[CharlieNC]

Good vibrations. ....

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

Within the large single harmonic as shown by Kolbe, I find multiple nodes as suggested by OBT. While I don't necessarily agree with the proposed mechanism, the reality is the multiple calculated nodes have always been in reasonable agreement with the target better than the other vibration methods. A better methodology to address positive compensation is needed and I'm not knowledgeable enough to develop it, but would love to use it.

 

[Bart B.]

A better methodology to address positive compensation is needed and I'm not knowledgeable enough to develop it, but would love to use it.

Varmint Al's site linked in post 4 shows realistic barrel vibration stuff.

 

[RW]

Thank You to everyone for their feed back, I think the simple answer is trying to get the powder that fills the case to capacity, some where around 100% and has good velocity, then Shoot the ladder test and record data and try and find the node that it likes. I have looked thru all my data and It seems to correlate with the powder that is around 100%. I tried looking at the barrel harmonic articles and I could get pretty confused quick! That is way over my head. I hope I can find a powder that is performing the best with out trying every one as I have quite a few powders to choose from, Thanks Again, RW