Seating depth variation

[RichCoyle]

If you shoot larger samples sizes, 20-30, you will see that the group shape is not changing. Small sample size group (3-5 shot) shape changes are just random bullet dispersions within the cone of fire. It is all laid out in the studies I posted and makes perfect sense when you think about it.

I am not saying that your method of reloading doesn't produce results. It obviously works for you, without dispute. What I am saying is that it may not work for the reasons you believe, and that there may be an easier way to get the same accuracy results with a lot less work. I assume your time and resources are valuable to you, I know that mine are. If I can get the same results with fewer steps and less work, then I am all for that. For me, the way to do that is to science the @#$% out of it. I am simply trying to share some real world, science based information that, while it goes against some long held dogma in reloading, has been proven through the scientific method and may save you some time and resources.

How does firing larger sample sizes save time and products?

 

[RichCoyle]

It's interesting that Berger recommends doing a seating depth test when from what I have read here it really doesn't matter.
I have been using the Berger method with most bullets nowadays and I have seen the results and I believe results.
As far as science goes, I have a hard time believing MOST so called scientists. Most seem to be pushing a agenda instead of actual science. JMO

Maybe some of us remember, "Trust the science."

 

[VenatusDominus]

Science ? How about 6 years of actual shooting in a controlled 350 yd warehouse precisely measuring the effects of reloading methods over tens of thousands of rounds? The cliff notes: " if you change the bullet seating depth or the grip on the bullet, you're going to see bad things happen fast."

Secrets of the Houston Warehouse – Lessons In Extreme Rifle Accuracy

Back in 1993, Precision Shooting Magazine printed a landmark article about the findings of a group o...

precisionrifleblog.com

I tried to read the 9 page PDF but was not able to download it. The author of the cliff notes touches on seating depth but does not give details about "bad things" so very difficult to evaluate. Everything else in the study, based on the cliff notes, seams to agree with the findings from those I referenced. The article and podcasts I shared are also actual shooting, not some theoretical exercise.

 

[birddog 68]

I will admit that I didn't watch any videos.
If I shoot a 3 shot group with A seating depth and the group measures 1.5" and a group using B seating depth and it measures .75 are they saying that it doesn't matter which I use? Of course the .75 will be larger after shooting 30 shots BUT it stands to reason that the 1.5 will also be larger in size or will that one stay 1.5?

 

[birddog 68]

Maybe some of us remember, "Trust the science."

Exactly!

 

[VenatusDominus]

I tried to read the 9 page PDF but was not able to download it. The author of the cliff notes touches on seating depth but does not give details about "bad things" so very difficult to evaluate. Everything else in the study, based on the cliff notes, seams to agree with the findings from those I referenced. The article and podcasts I shared are also actual shooting, not some theoretical exercise.

How does firing larger sample sizes save time and products?

Instead of doing a ladder test with 10 rounds and then shooting 3-5 round groups at 5 or six seating depths, they shoot a few rounds (3-5) at 1-2 grains below publishes max (for cartridges with case capacity about 40 grains). They just load at .025" to 0.35" off the lands, keeping the seating die consistent between loads. If the powder bullet combo does not produce a small group under say .5" then they change the powder or bullet (groups are only going to grow in size with additional data points). Once they find the bullet/powder combo that produces a small sample size in the desired range, they then shoot a 20-30 shot composite group to get the true mean size of the load and are done. They now know what their hit probability is on a given target size at a given range and also know where the true center of the group is at. There data over thousands of real world shots demonstrated that changing the seating depth did not change the group size with groups over 30.

For every rifle there is a cone of dispersion and there are many factors that affect dispersion. You can have a 1 MOA cone of dispersion for a given load over 30 shots, but if you only shoot 3-5 shots per group, you can easily get groups that all hit within .25" of each other. Most people, including myself, then assume that the rifle is a quarter MOA shooter and when they get something outside that, ie a flier, they chalk it up to pulling the shot, or wind or some other factor. When in reality the flier is in the normal cone of fire for that load. Shooting a statistically valid number of shots is the only way to truly know the true cone of fire for a load.

 

[VenatusDominus]

Maybe some of us remember, "Trust the science."

I am a physician and remember well. The problem was the government was suppressing any scientist that dissented from what they wanted the public to know. That is not science! That is the opposite of science. Science is the open and free sharing of information.

We have the same problem in medicine as in shooting, decades of tradition and dogma, much of which has no scientific basis. In the early 2000's there was a movement in medicine to what is called evidence based medicine. It was largely driven by insurance companies not wanting to pay for treatments that did not work. So now treatment is driven by scientific evidence rather than by "this is how it has always been done."

I knew that Dr. Fauci was a quack when, with respect to wearing two masks, he announced on national television that "it just makes common sense that it likely would be more effective". That is not the type of medicine we practice today. Modern physicians what to know where the randomized, double blind, placebo controlled scientific study is that demonstrates two masks are better than one.

 

[VenatusDominus]

I will admit that I didn't watch any videos.
If I shoot a 3 shot group with A seating depth and the group measures 1.5" and a group using B seating depth and it measures .75 are they saying that it doesn't matter which I use? Of course the .75 will be larger after shooting 30 shots BUT it stands to reason that the 1.5 will also be larger in size or will that one stay 1.5?

Any group size is not going to get smaller with more shots. The 1.5" inch group may have been the two worst shots if you add another 27 to the groups, possible, but not statistically likely. Similarly the .75" group could be the tree smallest in a group after adding another 27 to the group, again possible but not statistically likely. To accurately know the cone of dispersion your rifle is actually producing you need a minimum of 20 shots and 30 is even better.

 

[Willys]

Any group size is not going to get smaller with more shots. The 1.5" inch group may have been the two worst shots if you add another 27 to the groups, possible, but not statistically likely. Similarly the .75" group could be the tree smallest in a group after adding another 27 to the group, again possible but not statistically likely. To accurately know the cone of dispersion your rifle is actually producing you need a minimum of 20 shots and 30 is even better.

I wonder if I can get animals to hold for 30 rounds? Guess I'll just stick to 3 round groups……

 

[VenatusDominus]

I wonder if I can get animals to hold for 30 rounds? Guess I'll just stick to 3 round groups……

If you know what your rifles cone of dispersion is, you only need "animals to hold for" for 1 shot. You cannot possible know what the cone of dispersion is (actual group size) without firing enough rounds to produce a statistically accurate bell curve. From that data you can calculate the mean radius and then calculate the standard deviation and know that ~68% of your shots will fall within one standard deviation (SD) of the mean radius, ~95% within 2 SDs and ~99.7~ within 3 SDs. Whether shooting PRS or at game, knowing your hit probability for a given target size at a given distance is very helpful. It allows you to better understand when you miss a target that is smaller than your mean radius, your miss is statistically within the realm of possibilities for your cone of dispersion and you may not need to adjust or tinker with your aim. Or if you miss and your target is 2 SDs the size of your mean radius, then you know with 95% certainty that you should have hit and need to adjust your aim.

 

[VenatusDominus]

I wonder if I can get animals to hold for 30 rounds? Guess I'll just stick to 3 round groups……

The purpose of this forum is to share information that might be beneficial to others and then have a discussion about it. That is all I did by posting links to an article and two podcast. Did you read the article or listen to the podcasts? If you did, I would honestly be interested in your comments on them. If not, then I am not sure why you are shooting down (pun intended) the information I presented.

 

[RichCoyle]

I knew that Dr. Fauci was a quack when, with respect to wearing two masks, he announced on national television that "it just makes common sense that it likely would be more effective". That is not the type of medicine we practice today. Modern physicians what to know where the randomized, double blind, placebo controlled scientific study is that demonstrates two masks are better than one.

My wife was a "health and safety" coordinator. The company had a finish department where sealer and lacquer were sprayed. She didn't allow anyone with a beard to even try out for the jobs. They had to use face fitting respirators. She told me trying to catch a virous with one of those masks was like trying to stop a mosquito with a chain link fence.

 

[Equalizer]

I'm gonna watch the videos and read the outdoor life article but more data does make sense.

It reminded me of an article on finding the cold bore zero for a given rifle and load I read years back. I believe it was Carlos Hathcock's method…. it was a single shot at the same target on different days and in different conditions or elevations. The shooter takes notes and keeps the targets to overlay one another and continues to add to the data. It is different but similar in that your plotting the cone of fire and learning the predictability of your system in "all" conditions and circumstances for first shot hits.

 

[Equalizer]

Carlos Hathcock Method of Sighting in a Rifle

Carlos had me Shoot 1x/day & record everything into a log book, the Rationale was that "How many shots do you think you are going to get at a deer?"

americanshootingjournal.com