Been doing some reading/research on the harmonics of a barrel. I have known for some time about harmonics but I read a new note to reloading. 
When fired, the bullet/pressure produces an annular ring to travel the barrel...and back. This expanded ring will actually increase the diamter of the bore when the ring reaches the muzzle.
Heard of it?

Jeff_Schultz wrote on Aug 26^th, 2018 at 8:55pm:


I have to ask if this really improves accuracy or is it just another bit of lore and confidence building mythology? If the last bullet cast is identical in appearance, weight, and  BHN to the first why won't it shoot to the same place on the target? I have tested my bullets and once I get things up and running during a casting cycle I don't see any difference between the first bullet saved and the last. Of course, maybe that's why my groups aren't as small I'd like either!

JS

"That's why we shoot our bullets in the order cast."

Isn't this dependent on being able to cast bullets within a couple grains of each other? And, if so, I cannot grasp the importance of "order cast". Please break it down to finer points of why.

"I would start with 10 loads of powder with each load separated by 0.1 grains to indicate three possible nodes.

Are you saying that you loaded ten rounds    and each round was 0.1 grain heavier than the last? Would the ten rounds group tighter and tighter?

The tightness of the groups would indicate if I should go up or down to the next node for better accuracy."

Please explain "tightness" and how it decided up or down.


You started with a known load, I suppose, and fine tuned it from there? 

Please continue. This is very interesting.

A question for Schuetzen Dave. When you are doing this testing of powder volume does the barrel rest position enter into the equation? I know that I can introduce a lot of vertical by varying the rest position. I look for a round group rather than one that is strung out but I can introduce vertical just by varying shoulder pressure on the stock. All this gets pretty confusing. Some days I shoot groups that I make the mistake of bragging about and the next day I completely blow it!

JS

What I have found with .32 caliber bullets is that as I shoot when I find a sweet spot (where vertical stringing stops) I can find another sweet spot about 110 FPS of velosity further up. This will usually give me 3 to 4 spots before case sticking sets in. Then the choice becomes which out of those 3 t0 4 spots gives me the most consistancy.

40 Rod

And, I believe, you also breech seated the bullets, correct?

Do you ever resize a bullet? I would guess a breech seated bullet is shot as cast since it is cast to certain specs to fit the throat/leade/freebore/lands, and grooves.


And since you breech seat, case prep is somewhat of a breeze.

Got a lotta work to do. And try to think of more questions. 

Thank you, Schuetzendave, for your help. I have struggled for months and I think you have started to open the door for me. 

I also shoot my bullets in weight-order from heaviest to lightest to keep shot-to-shot weight variation to a minimum.

When I load-test for a new rifle I start with enough powder to just give me about 0.050" of powder compression and then I keep increasing the power in a about 2 grain increments up to the point where the compressed powder starts to bulge the case. For all my BP rifles (Hepburn, Stevens, Highwall). I have found two powder weights that give the best accuracy: 63 and 70 grains. As the powder increases from 63 grains the groups start to open up but then go back down as I approach 70 grains. This is for both 45-70 and 40-65.

I rest my barrel on my cross sticks at the null point 8" back from the muzzle. I have found recently that if I relieve the forearm so that no wood touches the barrel or the front of the action, I get consist accuracy. Only the forearm attachment escutcheon "touches" the barrel. My attempts of testing accuracy off the bench at 300 meters I was able to put the first 3 shots almost through the same hole until things started to open up. This was before I relieved the forearm wood. Groups now, with the wood relieved, on targets out to 500 meters, over cross-sticks, are pretty darn tight.

John, why do you believe that the amount of tin changes during the course of casting, say, 150 bullets? That number sounds like a average of your number.
I've never heard that explanation except during a long span of time without fluxing, but only skimming off the dross. That may remove some tin, but still, slowly. Just curious.
For what it's worth, I flux quite often, just to avoid that.