Composite groups?

[spitfire_er]

I have a pretty good grasp on my reloading techniques and have a system that works for me and many others producing very accurate loads.

In an effort to gain small tidbits of information here and there, I recently was watching an " internet expert" talking about his composite groups when doing load development. He was not doing ladder testing. I must qualify that I agreed with 90% of what the guy said but he completely lost me when he started talking about taking taking several charges and shooting one group. Example 34.5gr, 34.7 gr, 35.0gr 35.2 gr and 35.5 gr powder charges. He would shoot 1 of each into a 5 shot group.

Not sure what his end goal was, but the only advantage to doing this, other than wasting time and money, is to see where a node range MIGHT be. To further confuse me on his methods was that he didn't use a custom rifle but an off the shelf 700 CDL that he "Accurized".

Just wondering if im missing something. Is he just wasting time or is there something he is getting from shooting a composite group. I have always shot charge X into group X and so on unless doing a ladder test.

 

[T-shooter]

I have a pretty good grasp on my reloading techniques and have a system that works for me and many others producing very accurate loads.

In an effort to gain small tidbits of information here and there, I recently was watching an " internet expert" talking about his composite groups when doing load development. He was not doing ladder testing. I must qualify that I agreed with 90% of what the guy said but he completely lost me when he started talking about taking taking several charges and shooting one group. Example 34.5gr, 34.7 gr, 35.0gr 35.2 gr and 35.5 gr powder charges. He would shoot 1 of each into a 5 shot group.

Not sure what his end goal was, but the only advantage to doing this, other than wasting time and money, is to see where a node range MIGHT be. To further confuse me on his methods was that he didn't use a custom rifle but an off the shelf 700 CDL that he "Accurized".

Just wondering if im missing something. Is he just wasting time or is there something he is getting from shooting a composite group. I have always shot charge X into group X and so on unless doing a ladder test.

Beats me! Can you post the link to the video?

 

[Keith Glasscock]

Based on your description, it sounds like he is testing for positive compensation.

I haven't seen the vid, so anything is possible.

 

[spitfire_er]

It's between 44:00 and 46:00. I went back and watched it again and I guess he was trying to make a point that throwing charges from a RCBS powder throw is accurate enough at 100 yards for MOA accuracy within a few grains of powder.

Not good enough for me in F-class shooting, but I guess he's happy with it for a standard rifle.

 

[T-shooter]

I have a pretty good grasp on my reloading techniques and have a system that works for me and many others producing very accurate loads.

In an effort to gain small tidbits of information here and there, I recently was watching an " internet expert" talking about his composite groups when doing load development. He was not doing ladder testing. I must qualify that I agreed with 90% of what the guy said but he completely lost me when he started talking about taking taking several charges and shooting one group. Example 34.5gr, 34.7 gr, 35.0gr 35.2 gr and 35.5 gr powder charges. He would shoot 1 of each into a 5 shot group.

Not sure what his end goal was, but the only advantage to doing this, other than wasting time and money, is to see where a node range MIGHT be. To further confuse me on his methods was that he didn't use a custom rifle but an off the shelf 700 CDL that he "Accurized".

Just wondering if im missing something. Is he just wasting time or is there something he is getting from shooting a composite group. I have always shot charge X into group X and so on unless doing a ladder test.

I understand what he is talking about. He kept 1 round from each of his various loadings and fired them at one target to demonstrate that the powder change differences didn't vary the impact to any great degree. I disagree with him because it doesn't always work out that close. I found an old target and I think I was using Hornady 168g Match bullets at 100 yards. Also, some old CBC cases which were junk. Still differences in powder charges moved the hits around moving upwards and slightly to the right.

 

[spitfire_er]

I understand what he is talking about. He kept 1 round from each of his various loadings and fired them at one target to demonstrate that the powder change differences didn't vary the impact to any great degree. I disagree with him because it doesn't always work out that close. I found an old target and I think I was using Hornady 168g Match bullets at 100 yards. Also, some old CBC cases which were junk. Still differences in powder charges moved the hits around moving upwards and slightly to the right.

That is basically the experience that I have had. You ether hit a node, get close, or not at all.

 

[T-shooter]

That is basically the experience that I have had. You ether hit a node, get close, or not at all.

If I were working that load, I now go to about 42.4, 42.6, 42.8, 43.0, 43.2 and shoot 5 shot groups each and see if that showed me anything.

 

[spitfire_er]

If I were working that load, I now go to about 42.4, 42.6, 42.8, 43.0, 43.2 and shoot 5 shot groups each and see if that showed me anything.

Agreed

 

[dsculley]

You guys are missing the point. If you had watched the video you would have learned that he did this to prove a point. He uses a powder measure for his charges once he has settled on a load. He knows that he can throw charges that vary no more than +/-0.1 gr. He shot this group with one round from each test load to prove how little difference that will make. The load he was using was shooting 3/8" if I remember correctly. The "composite group" was still under 1". I did kinda the same thing recently. I shot a 3 shot group of my selected load and 2 rounds +/-0.1 gr. All three were in the same group as the original 3 rounds of the single load. Proof that this was truly a node, not just a "good group".

I know some of you are gonna say that charges thrown with a measure can't be as consistent as those that are weighed. I once did a blind bag test to check this. I shot 20 rounds that were weighed and 20 that were thrown with a powder measure. All were shot over a chronograph. I computed MV SD for each group. I measured vertical and horizontal dispersion for each group. I computed SD for horizontal and vertical dispersion. There was no significant difference between the groups for any of these parameters. I still have the targets out in my shop, but if I recall correctly these were shot at 200 yds as that was the longest available at this range and the groups were under 0.5 moa vertical. There was a bit more horizontal as there was a gusting wind that I was not trying to adjust for in this trial.

Now, before you tell me that this can't be perhaps you should try your own brown bag test. This involves having someone label the containers to identify which is weighed/thrown in a manner that you don't know which is which. That way you won't subconsciously try to affect the results. I shot this test round-robin to even out the wind dispersion. Load enough rounds to be statistically significant. 20 is a good start.

By the way, neither ES nor SD is statistically significant for 3 rounds. You can use the chronograph on multiple range trips to gather more data and then use Excel to compute the statistics. When your data set is large enough, the true ES of your load is 6 times the SD. The SD is much more important than the ES of a particular data set. That ES is significant only to that data set. The next time you run the load over a chronograph don't be surprised if the ES is much different.

FWIW,

Dennis

 

[Tiratore]

On the side-topic of weighed versus metered charges ....

This table results from a test of metered versus individually-weighed charges for the 20 VarTarg with H-4198. The first two columns show chronograph results with charges "trickled." The last two columns represent velocities for metered-charge rounds.

A previous test in a .222 showed no benefit to individually weighing charges of H-4198 but IMR-4198 showed a benefit to weighing. I guess it depends on granule geometry, case volume, charge density or some such.

Sorry about the fuzzy image.

 

[dsculley]

View attachment 1012297

On the side-topic of weighed versus metered charges ....

This table results from a test of metered versus individually-weighed charges for the 20 VarTarg with H-4198. The first two columns show chronograph results with charges "trickled." The last two columns represent velocities for metered-charge rounds.

A previous test in a .222 showed no benefit to individually weighing charges of H-4198 but IMR-4198 showed a benefit to weighing. I guess it depends on granule geometry, case volume, charge density or some such.

Sorry about the fuzzy image.

It is interesting to note that you got the best results with a beam scale over the electronic. I am not surprised, as I have seen this as well. I was using the Lee Perfect Powder Measure. Powder measures do take some work on technique to be consistent. How did the targets look?

Depending on how powder is stored, it can either pick up moisture or lose moisture over time. New powder may still be off-gassing acetone used in the manufacturing process. A charge of powder that is weighed when the canister is first opened may be different from a charge weighed six months later. If you record the volume of the charge, that will remain consistent.

Just one more thing to consider.

Dennis