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Confused by powder test results!

Normally velocity data like shown would tend to indicate to me that your barrel was too clean and took around 20 rounds to stabilize. What strikes me is your desire to wait 10-15 minutes between strings. I don't usually do that and I don't know of anyone that does (not saying everyone doesn't). In testing this can lead to some temporal effects that might be happening. Obviously the temperature of the round has more opportunity to change. The barrel fouling may be sensitive to temperature or humidity. If using an optical chronograph then lighting is changing.

Depending on how the rounds are stored and loaded into the gun can have an effect especially at lower case fills.

While probably not likely it's possible that if the rounds were shot in the order that they were loaded then a scale/measuring issue might be causing this behavior.

My point is that there are multiple factors that might be causing this and it's not likely that we can identify what is causing it from this one test.
 
Take a look at the vids from Little Crow Gunworks reloading series on YT, he just put out his conclusions vid on it, if you are more curious, look at the whole bunch. He explains it pretty damned well as far as I'm concerned, I can agree with about 95% of his methods and maybe better than that with his conclusions.
 
Normally velocity data like shown would tend to indicate to me that your barrel was too clean and took around 20 rounds to stabilize. What strikes me is your desire to wait 10-15 minutes between strings. ...

While probably not likely it's possible that if the rounds were shot in the order that they were loaded then a scale/measuring issue might be causing this behavior.

With 35+ rounds to shoot in the test I didn't want to burn out my barrel by shooting them all in just a few minutes. I figured giving the barrel a chance to cool a bit between series was a good thing.

No, the rounds were not shot in the order they were made.
 
With 35+ rounds to shoot in the test I didn't want to burn out my barrel by shooting them all in just a few minutes. I figured giving the barrel a chance to cool a bit between series was a good thing.

No, the rounds were not shot in the order they were made.
I would have done the same as you, guess I been wrong also
 
Shooting more, clean less. The barrel is fully settled, so, no need to clean that often. In a 6br with a good barrel, you could go 400 rounds between cleaning if you wanted, I myself prefer 150-200. You also might not be in the sweet spot you think you are. I also believe N130 is a little fast, even with 70 grainers, I believe I'd try H322, Benchmark, N135, or even something as slow as 8208xbr or H4895. The slower the powder you can get away with, the wider your sweet spots will be. You may think this is insane, but I've had some success with Staball 6.5 and 109 Bergers in a straight 6br, although I need to test more. My normal powders iare also slower than what most people use, RL17 and PP2000MR.
 
I've done the 'zig-zag' method before as well. Sometimes I'd run into a similar problem, but, when I found a good charge, it was usually consistent after that. OTOH, the results were sometimes really wrong.

I stopped using that method for a variety of reasons. Instead I just allow a lot of time between groups and I limit them to 3 shots instead of 5. I do make sure barrel temp is same and barrel is fouled and warm before starting. I also have a 6BR and it is usually good for 200 rounds before cleaning. Sometimes I will repeat the ladder on another day just to verify the results, and make sure I wasn't the problem. :)

FWIW, I've used Varget, N150 and N540 with 105gn bullets. I get similar results with all three powders.
 
Howdy folks,

I recently did a powder test for a load and I'm having a hard time comprehending the results. I'll try to describe the process as best as I can and I'll leave out unimportant details to keep things short as possible.

I loaded five rounds of each load, 0.2 grains apart, which I will call A, B, C, D, E, and F. At the range I had a target with a common horizontal line and separate vertical hash marks so I could see any vertical shift and I ran my chronograph for the whole test. Wind was sub-5 MPH and I had a wind flag at ~20 yards.

After five sighter/fouler shots, I shot one shot of load A at the first hashmark, then one of B at the second, C, D, E, and F. I let the gun cool about 10-15 minutes, then ran the second shot for each load starting with F, then E, D, C, B, and back to A. Let the gun cool, then shot A-F again, continuing until I had run the full series for five shots for each of the six loads in this zig-zag manner.

When I loaded the chrono data into a spreadsheet, I rearranged the info so I could graph load A shots 1-5, then load B shots 1-5, etc. This is where things get weird...

The first two shots of each load are significantly lower than the next three, like 60 to 75 FPS lower. Across all six loads, all of the first two shots are lower than the velocity jumps for the next three, and with a few exceptions, the velocity continued to rise slightly as the test went on. (The chrono didn't capture the last shot on load F.)

View attachment 1673184

Oddly enough, I shot five rounds of two other loads right after this test and they did not exhibit this increasing-velocity behavior.

No, this is not a new barrel, it has about 1,200 rounds on it. Yes, the barrel was cleaned after the previous range session as usual.

The targets didn't seem to show any obvious correlation between the jump in velocity between series 2 and 3. (Unfortunately, I didn't seem to have a clear winner with the loads, so that's annoying as well.)

Any thoughts on what is going on here?
I know some pretty good shooters, and none of them use the method that you have described to work up an accurate load. Generally speaking I think that it is a good idea to copy the folks that get the best results, and the best indication of who those folks are is match results.
 
Lots of good feedback above.
  • I don’t do these round robin, I shoot all rounds of one powder charge in less than 20 seconds
  • If 5 shots per charge, I only do 4 charges
  • Seems like barrel was too clean (happens if Iosso or JB is used)
  • This test took over an hour to complete, weather variables could have changed a lot.
 
Howdy folks,

I recently did a powder test for a load and I'm having a hard time comprehending the results. I'll try to describe the process as best as I can and I'll leave out unimportant details to keep things short as possible.

I loaded five rounds of each load, 0.2 grains apart, which I will call A, B, C, D, E, and F. At the range I had a target with a common horizontal line and separate vertical hash marks so I could see any vertical shift and I ran my chronograph for the whole test. Wind was sub-5 MPH and I had a wind flag at ~20 yards.

After five sighter/fouler shots, I shot one shot of load A at the first hashmark, then one of B at the second, C, D, E, and F. I let the gun cool about 10-15 minutes, then ran the second shot for each load starting with F, then E, D, C, B, and back to A. Let the gun cool, then shot A-F again, continuing until I had run the full series for five shots for each of the six loads in this zig-zag manner.

When I loaded the chrono data into a spreadsheet, I rearranged the info so I could graph load A shots 1-5, then load B shots 1-5, etc. This is where things get weird...

The first two shots of each load are significantly lower than the next three, like 60 to 75 FPS lower. Across all six loads, all of the first two shots are lower than the velocity jumps for the next three, and with a few exceptions, the velocity continued to rise slightly as the test went on. (The chrono didn't capture the last shot on load F.)

View attachment 1673184

Oddly enough, I shot five rounds of two other loads right after this test and they did not exhibit this increasing-velocity behavior.

No, this is not a new barrel, it has about 1,200 rounds on it. Yes, the barrel was cleaned after the previous range session as usual.

The targets didn't seem to show any obvious correlation between the jump in velocity between series 2 and 3. (Unfortunately, I didn't seem to have a clear winner with the loads, so that's annoying as well.)

Any thoughts on what is going on here?
Hi Allen,
As usual, with these questions I feel like we are like the proverbial 3 blind men and the elephant.

The barrel heat, air temperature and fouling are some of factors that can influence velocity, but there are more.

I would like to ask more questions, before I venture with an answer. Barrel harmonics and velocities are major factors, major contributors are caliber, barrel length and bullet weight. I use Quick Load to find out where the harmonic nodes are and then do my seating depth testing and finally tuner testing (if you use one). That works most of the times, but sometimes I just get a bad lot of powder that has a lot variance. Then there is brass prep, bullet sorting, primer sorting. etc... It's enough to drive a guy mad.

Joe
 
Ok I read some of this again and thought I’d offer another 2 cents.
If I understand correctly you shot load 1a,1b~
Then 2e,2d~ and repeated this.
In my opinion you are still shooting .2-.10 grain loads in session then letting barrel cool.
So the barrel is either dirty or clean each session and with cooling time air temp is continuously rising equally between sessions. Unless your barrel can’t handle a five shot group there shouldn’t be much variation between sessions whether you ran the test Abcde or edcba fowling and air temp are going to be similar. I would suspect your shooting a very temp sensitive powder or your barrel is so cracked out it is fowling out way to soon. Was the second test a different powder? Or had air temp peaked out? I have to think it’s either barrel fowling or powder sensitive. I guess there’s also the chronograph I don’t know what chrono you’re using. If it was a light sensor style they shift as sun moves around. This is one of the things that is very hard to figure out without all the info used in test. Whatever it is you probably just need to trash that load.
 

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