How it works and why it doesn't...

How it works and why it doesn't...

This is a discussion on How it works and why it doesn't... within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I'm sure the looming question on everybody's mind during the Thanksgiving Holidays is, "How many shots do I have to shoot before I reach the ...

Results 1 to 12 of 12
Like Tree19Likes
  • 4 Post By Tangle
  • 3 Post By G26Raven
  • 1 Post By OldVet
  • 1 Post By Smitty901
  • 2 Post By G26Raven
  • 1 Post By Smitty901
  • 2 Post By Tangle
  • 1 Post By Tangle
  • 2 Post By Smitty901
  • 2 Post By Tangle

Thread: How it works and why it doesn't...

  1. #1
    Lead Moderator
    Array Tangle's Avatar
    Join Date
    Dec 2004
    Location
    Chattanooga
    Posts
    12,936

    How it works and why it doesn't...

    I'm sure the looming question on everybody's mind during the Thanksgiving Holidays is, "How many shots do I have to shoot before I reach the maximum spread?" I am right about that aren't I? That is what was on your mind over the holidays??? Sooo, I set out to resolve this troubling concern.

    My approach was to shoot 25 rounds in 25 Winchester cases and 25 more rounds in Lapua cases. The results are in the table below. Although this is velocity data, that the data could very well be accuracy and the same principles apply. For now ignore the ES/shot columns, I'll get to that later.

    I calculated the spread for each 5 shot group, and this is the actual data as shot, and in the order the rounds and groups were shot.

    As we look at the differences in the 5 shot groups, it becomes clear that the 5 shot groups can be very misleading. Are the higher spreads more indicative/predictive, or are the the lower spreads more indicative/predictive? For example looking at the Win data, what if the last three groups happened to show up first? I would have been in reloader's heaven, thinking three 5 shot groups produced spreads in the low to mid 20's! But sooner or later those wider spread groups would show up. While a bit off subject, it is interesting that the inexpensive Winchester brass produced significantly smaller velocity variations than the Lapua brass.

    But, back on topic...here's the data in the order shot.



    What I haven't told you, that I will now, is that I shot all 50 rounds the same day, one shot right after the other with about a 30 second delay between shots and a bit longer between 5 shot groups. Also, I shot 5 Winchester, then 5 Lapua, and repeated that pattern until all 50 rounds had been shot. So the environmental effects are all the same.

    The other thing I haven't shown you, which I will now, is the overall spreads, i.e. the ES for the entire 25 shots for each case brand, well here that is - same table as above but down at the bottom of the table are the overall numbers. Pretty revealing isn't it! I mean the overall looks a lot different than the individual 5 shot groups. Although, having said that, the first 5 shot group of the Win cases is very close to the overall. But that's just the way it happened this time. Notice for the first 5 shot group for the Lapua cases, ES = 30 fps, would be very misleading as compared to the overall. And that's especially true for the second Lapua group that turned in a ES = 13 fps!



    Now let's go back to those ES/shot columns. These columns show how the ES progressed from shot to shot. These ES values are calculated by subtracting the lowest value from the highest value of the current shot. That's a little confusing I know but if I shot say, 9 shots, I found the low and the high those 9 shots and subtracted. With each shot fired, a new ES is calculated. The goal here is to see how many shots have to be fired before the maximum ES is reached.

    And what a stark difference between the Win and Lapua. For the Win cases the max ES was reached by the 8th shot. Of course I couldn't know that when I was shooting, because I wouldn't know what the max ES would be until the last shot was fired. But, for the Lapua cases, the maximum ES didn't show up until the 24th shot!

    If I had stopped at the with 5 shots or even better with the first 10 shots with the Lapua, I would think I had a fantastic performer, I mean an ES of 30 on the first group and an ES of a mere 13 fps from the second group! Wow! How good would that be! But, larger numbers reveal the truth. At the end of 25 rounds the ES was waaaay higher than those first two sets of 5.

    So now, as you're laying that sliced turkey on your bread to make a leftover sandwich, there can be one less thing on your mind. It takes 25 shots to really reveal the performance of a load/gun - maybe???

    Today, I plan to load up 40 rounds and see where/when the max ES occurs. The theory here being that if you shoot enough rounds, the ES will reach a max and no matter how much you shoot after that, the max will not increase. So, how many rounds does it take? I don't know, but if I shoot 40 rounds and the max occurs before the 40th round, I'm gonna go with 40 rounds. And, we could see that the max occurs in 25 rounds - gonna be interesting!
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  2. #2
    VIP Member Array G26Raven's Avatar
    Join Date
    Mar 2012
    Location
    Southwest
    Posts
    7,940
    But, Tangle, the barrel was cold on the first shot, and did you record the time between each shot? And, how did the air temperature change over the course of 50 shots? What about the humidity? The wind speed? The coriolis effect? Where is the data?
    Smitty901, Tangle and LimaCharlie like this.
    You are your own first responder.

  3. #3
    VIP Member Array OldVet's Avatar
    Join Date
    Nov 2009
    Location
    The Florida Twilight Zone
    Posts
    32,928
    I'm not ready for this yet...

    I can't remember what the shot-string limit on my Magnetospeed sporter is, but that will be the limit of how many rounds I can use to establish any data. I'm too lazy to break out a calculator.
    Smitty901 likes this.
    Retired USAF E-8. Curmudgeon on the loose.
    Lighten up and enjoy life because:
    Paranoia strikes deep, into your life it will creep. It starts when you're always afraid... Buffalo Springfield - For What It's Worth

  4. Remove Advertisements
    DefensiveCarry.com
    Advertisements
     

  5. #4
    VIP Member Array Smitty901's Avatar
    Join Date
    Dec 2011
    Location
    Wisconsin
    Posts
    4,559
    Quote Originally Posted by G26Raven View Post
    But, Tangle, the barrel was cold on the first shot, and did you record the time between each shot? And, how did the air temperature change over the course of 50 shots? What about the humidity? The wind speed? The coriolis effect? Where is the data?
    Man that stuff will make your head hurt and keep you up at night.
    I try to keep it simple did I hit if no why not. If the answers is to far away I move closer or go get a bigger weapon. I do understand the game of trying to make better.
    G26Raven likes this.
    Yes Taurus really does suck. But in fairness they sure turned it around fast on warranty repair. Time will tell

  6. #5
    VIP Member Array G26Raven's Avatar
    Join Date
    Mar 2012
    Location
    Southwest
    Posts
    7,940
    Quote Originally Posted by Smitty901 View Post
    Man that stuff will make your head hurt and keep you up at night.
    I try to keep it simple did I hit if no why not. If the answers is to far away I move closer or go get a bigger weapon. I do understand the game of trying to make better.
    Agreed! I want to shoot as precisely as possible, but at the end of the day, as long as I put the animal on the ground with one shot, I am satisfied.
    Smitty901 and Tangle like this.
    You are your own first responder.

  7. #6
    VIP Member Array Smitty901's Avatar
    Join Date
    Dec 2011
    Location
    Wisconsin
    Posts
    4,559
    Quote Originally Posted by G26Raven View Post
    Agreed! I want to shoot as precisely as possible, but at the end of the day, as long as I put the animal on the ground with one shot, I am satisfied.
    It won't be this winter . I want to go nuts with the 338 lapua. I will be using factory match loads to play with. I have been shooting good 250gr round with it but not the match grade. I leave the reloading to my son now pack all the stuff up took it to his place a few years back. He will be home in 12 months or so.
    G26Raven likes this.
    Yes Taurus really does suck. But in fairness they sure turned it around fast on warranty repair. Time will tell

  8. #7
    Lead Moderator
    Array Tangle's Avatar
    Join Date
    Dec 2004
    Location
    Chattanooga
    Posts
    12,936
    Quote Originally Posted by G26Raven View Post
    But, Tangle, the barrel was cold on the first shot, and did you record the time between each shot? And, how did the air temperature change over the course of 50 shots? What about the humidity? The wind speed? The coriolis effect? Where is the data?
    Quote Originally Posted by Smitty901 View Post
    Man that stuff will make your head hurt and keep you up at night.
    I try to keep it simple did I hit if no why not. If the answers is to far away I move closer or go get a bigger weapon. I do understand the game of trying to make better.
    Clearly I have spoiled these guys so badly that they expect endless detail of test data and analysis.

    Actually @G26Raven is just funnin' with me.

    What i'm doing is more about finding the extremes for my gun/ammo combination. Once I know that, I know what I can expect to hit at what range. It's not so much about hunting, as most hunters encounter short ranges with huge targets. Although, hunting small game at long ranges is an entirely different thing. That's more the level I'm interested in. And, I like hitting dime-sized targets at 100 yards.
    G26Raven and Smitty901 like this.
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  9. #8
    Lead Moderator
    Array Tangle's Avatar
    Join Date
    Dec 2004
    Location
    Chattanooga
    Posts
    12,936

    I probably should clarify the purpose of all this...

    Some of you will be aware of this but the purpose of this type of testing is an attempt to explain some of the unexpected, if not unpredictable, results I have been getting.

    In a nutshell, I'd shoot 5 shot ladders and pick out the good group and load up around that charge. I'd go to the range and shoot that charge and +/- 0.1 gr charges with it. but the results, more often than not, did not look at all like the "selected" charge picked from the ladder. After repeated cycles of that, I decided to find out what was going on.

    I discovered what was going on was entirely due to the small sample size of the ladders. The way I confirmed this was to shoot as many as 25 shots and look at individual 5 shot groups as well as the overall stats. It became crystal clear what was happening - 5 shots could produce excellent results or ugly results and everything in between. IOW, I was getting false indications simply due to the small sample sizes.

    What this thread is about is simply to show the phenomenon and how we can get false indicators from small sample sizes, AND how large samples (~25 shots) can show us what we can really expect from our gun and ammo.

    This will by no means apply to the majority of shooters, but for those that want to know more about the consistent capabilities of their gun, then this should illustrate how to determine the limits of our gun and ammo.

    I didn't get to the range yesterday, but hopefully today, so I can shoot a 40 shot string. The 40 shot string is to see if the ES has topped out within the 25 shots in this test or if it continues to increase with more shots. I hope not!

    In a "mathy" perspective, 40 shots more than meets the requirement for applying the Central Limit Theorem for non-normal data distribution. That theorem allows us to treat non-normal distributions as normal (sort of). So just in case my data isn't quite bell shaped, I have enough data to use the same analysis methods.

    So where does this take me? Once I know where the 97% - 99% (two and three SDs) points are, I will be able to determine worst case scenarios for velocities and POI shifts due to velocity variations. Also, it will give me a really good idea of what the probability is of getting an outlier and how by how much it will vary from the average - whether the "it" is accuracy or velocity.

    What will I do once I know all this? Well, now that I know what I'm doing - finally - I will have a way to generate valid data for accurately comparing one gun/load to another. For example, is my 14.5" BSF carbon fiber barrel any more accurate AND consistent than my BCM 11.5" Light Weight Enhanced barrel? Is 8208 XBR more consistent than Ramshot TAC?
    G26Raven likes this.
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  10. #9
    VIP Member Array Smitty901's Avatar
    Join Date
    Dec 2011
    Location
    Wisconsin
    Posts
    4,559
    We went through something like this last year. looking for the round that would split the difference and work best in two different weapons. 308's AR10 18 inch and a bolt action Ruger American . Goal was simple minute of man at 400 yards. And function in both weapons 100% of they time. Lower recoil loads were some what desired for the semi auto , but enough to make it function. We have long been 308 shooters and own a lot so finding rounds that work the best in everything is an advantage. This next year we play with the 6.5 CR and the 338's
    The first loads were to light and cause issue with the AR10. In the end we found pretty much any good factory loads 150gr to 180 worked well. and the 180 won out by a slight bit in accuracy . It was fun
    G26Raven and Tangle like this.
    Yes Taurus really does suck. But in fairness they sure turned it around fast on warranty repair. Time will tell

  11. #10
    VIP Member Array G26Raven's Avatar
    Join Date
    Mar 2012
    Location
    Southwest
    Posts
    7,940
    Smitty901, I have exactly the same situation. I have a Bergara bolt gun in .308 and a Barrett AR10 in .308. I am using the same load in both rifles, 44.5 grains Varget with Nosler 150 grain Accubonds. Obviously, the velocity is a bit different as the Barrett has a shorter barrel but I achieve pretty close to the same precision with the same load in both of them. I am getting minute of deer out of both rifles at 300 yards.
    You are your own first responder.

  12. #11
    Lead Moderator
    Array Tangle's Avatar
    Join Date
    Dec 2004
    Location
    Chattanooga
    Posts
    12,936
    Quote Originally Posted by Smitty901 View Post
    We went through something like this last year. looking for the round that would split the difference and work best in two different weapons. 308's AR10 18 inch and a bolt action Ruger American . Goal was simple minute of man at 400 yards. And function in both weapons 100% of they time. Lower recoil loads were some what desired for the semi auto , but enough to make it function. We have long been 308 shooters and own a lot so finding rounds that work the best in everything is an advantage. This next year we play with the 6.5 CR and the 338's
    The first loads were to light and cause issue with the AR10. In the end we found pretty much any good factory loads 150gr to 180 worked well. and the 180 won out by a slight bit in accuracy . It was fun
    That's what it's about - fun combined with finding out what to expect from our guns and ammo. Although my efforts feel more like work than fun right now, but there's light at the end of the tunnel at least now.

    Sounds like our goals are similar - we just have different parameters. Your's is reliability and minute of man at 400 yards, mine is a dime at 100 yards and ES in the 30s to help with 500 yard shots.
    G26Raven and Smitty901 like this.
    We don't have a gun problem in the US, We have a people problem.
    The problem we have is people that want to kill large numbers innocent people
    in Gun Free Zones.

  13. #12
    VIP Member Array Smitty901's Avatar
    Join Date
    Dec 2011
    Location
    Wisconsin
    Posts
    4,559
    Quote Originally Posted by Tangle View Post
    That's what it's about - fun combined with finding out what to expect from our guns and ammo. Although my efforts feel more like work than fun right now, but there's light at the end of the tunnel at least now.

    Sounds like our goals are similar - we just have different parameters. Your's is reliability and minute of man at 400 yards, mine is a dime at 100 yards and ES in the 30s to help with 500 yard shots.
    When it gets out to 500 yards the 30.06,6.5 Cr 338 and 50 come out of the case. I love my 308's but real world the 6.5 Cr kicks it tail. Companies like Hornady are making some affordable match grade ammo now day.
    Mounting a scope on a 6.5 right now.
    Yes Taurus really does suck. But in fairness they sure turned it around fast on warranty repair. Time will tell

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •