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OEHLER 84 vs OEHLER 71 Shotshell testers

Discussion in 'Shooting Related Threads' started by Dr.Longshot, Mar 25, 2013.

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  1. Dr.Longshot

    Dr.Longshot Banned Banned

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    For the technically inclined the following information. If you test a shotgun shell in a 3 inch chamber Vs a 2 3/4 inch chamber you will see a significan pressure rise. There were inaccurate data being given in an Model 71 as the was expected to provide a start, stop, signals in real time to indicate the passage of the center of shot mass, through 2 sensing coils.

    How could the MAGICAL BOX record the center of the shot mass, after the entire mass passed through the 2 coils? It was too late to send a signal of the center mass. The Model 71 was changed to trigger the trailing end of the mass, the trailing end is not the center.

    The Model 84 was designed and uses and oscilloscope to tune in the 2 coils.

    The first coil on a Model 84 is 1.5 feet from the muzzle to the 1st coil, and 3 feet to the 2nd coil.

    The Model 84 is set up to run only on Windows Pro computers.

    I don't know the model of OEHLER that was used in the shell testing and what the Bbl Chamber length was. But it should be measured in a trap Bbl with a 2 3/4 inch chamber for correct chamber pressures.

    So please go to the OEHLER Web site and read what it says on comparing the newest model#84 Vs older Model #71 from their website information the Model 84 is the most up to date model.

    Don't aske me anything just read the website, and see for yourself shot shell testing.

    I like first hand information from knowledgable sources and know where to get it.

    It is very interesting.

    Gary Bryant
    Dr.longshot
     
  2. Dr.Longshot

    Dr.Longshot Banned Banned

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    The Model 35 is for rifle loads.

    Gary
     
  3. Neil Winston

    Neil Winston Well-Known Member

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    The comparison is at the link above. I have found that the System 84 is far more stable than my earlier 71 which gave essentially the same results but required a lot more fiddling and cleaning and generally more tender loving care. The System 84 you turn on, let it warm up and stabilize for a few hours while the room warms up too, and then all you have to do is shoot.

    While the example system uses the -muzzle-to-coil distances cited by Gary, I use 1.5 feet to 4.5 feet since that is what I used with the Model 71.

    There are a couple of what I think are mistakes in Gary's post.

    1. "If you test a shotgun shell in a 3 inch chamber Vs a 2 3/4 inch chamber you will see a significant pressure rise."

    That is apparently based on the last test screen comparing "response to different shot materials." Traces 7 and 8 are made with Remington PHS1235HM shells. The Remington site is working too slowly today to dig up the information to be sure, but it seems likely to me that the shells were not 2 3/4's as Gary thinks, but rather 3 1/2,'s, especially since the note mentions "only"3" chamber."

    It would not make sense that a longer chamber would make more pressure.

    2. Gary wrote "There were inaccurate data being given in an Model 71 as the was expected to provide a start, stop, signals in real time to indicate the passage of the center of shot mass, through 2 sensing coils."

    I do not find that in the linked information. It does say that there were problems with .410 using full chokes. In fact, what is written is "This approach worked well for the larger bores with well-defined shot columns, " which is entirely different from Gary's characterization "inaccurate data being given in an Model 71." In posts intended for the "technically inclined" it's important to get things right, and what Gary wrote is not right.

    I use a cylinder choke which is not the SAAMI standard full choke, but I wanted to maximize my chances of getting the "well defined shot column" that Oehler specifies.

    Other than maintenance and occasional tuning my Model 71 worked great for years but finally began to fail. I would have gotten it fixed but Dr. Oehler told me that only Clyde still remembered how they worked and, being in retirement, only came in as it interested him. I got the System 84 instead and am glad I did.

    As I compare my current results with the Model 71 results of a dozen years ago I see that are just exactly the same, so I have not worried about the change in equipment biasing my results.

    Neil
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    3. The Model 35 is not just for rifle loads; it works well for shotguns too, though the "proof channel" is not much use. I use two units mounted on the same rail so I can hunt down the occasional bad reading. With my cylinder chokes bad readings almost never happen; with full chokes they are more of a problem.

    Neil
     
  5. Shooter R

    Shooter R Active Member

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    Hi Neil,it's always nice to read your posts. May I ask you a question? Does the velocity vary, and how much, between full and cylinder chokes?

    I see the logic of using a cylinder choke for chronographing. It would cause minimal "shaping" of the shot cloud, and pehaps give more consistant readings, as the leading edge "may" be more blunt, or in otherwords, more defined.

    I chrono my loads everytime I change lots of powder, sometimes with new primers, always to check the effect of temp extremes like 90's in the summer, and teens in the winter. I chrono at least every 2 months, I think it's fun.

    I use a large cardboard box, about 4 feet long, 2 1/2 feet wide, and about 2 1/2 feet tall. There is a one square foot opening in each end to shoot through. The top is open, but is covered with a single sheet of semi transparent plastic film. This difusses the light and I get consistant readings early in the day, later in the day, winter (low angle of sun), summer, sunny or cloudy. If you ever have issues using a chrono outside, this setup may help.

    Thanks for your contributions, Randy.
     
  6. oleolliedawg

    oleolliedawg Banned User Banned TS Supporters

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    I have a 35P taking up space in the garage. Is it any good??
     
  7. Dr.Longshot

    Dr.Longshot Banned Banned

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    Neil it specifically says when shooting a 2 3/4 inch shell in a 3 inch chamber the pressures are higher, they found it in their testing, read the OEHLER web site on the Model 84.

    Gary
     
  8. Neil Winston

    Neil Winston Well-Known Member

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    It may say that and I just missed it, Gary. Can you tell me exactly where I can find that? Exactly, because I always seem to blow right past it.

    As I say, it makes no sense to me that a longer chamber should lead to higher pressure readings, but I'm willing to listen to Oehler - after all, they build these things.

    Neil
     
  9. Neil Winston

    Neil Winston Well-Known Member

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    Randy, there are four effects of added choke on chronograph readings.

    1. When choke is tightened using an inductive chronograph, recorded shot speed drops about 25 fps between cylinder and full.

    2. When choke is tightened using a light-operated chronograph, recorded shot speed increases about 25 fps between cylinder and full.

    3. When choke is tightened using a light-operated chronograph, shot-to-shot variability between readings increases a lot.

    4. Because of 3., you need to use cylinder chokes with light-operated chronographs if you want to test the consistency of your reloads.

    I think your box is a good idea, Randy. I only test outside to see how it works so I'm not likely to get around to building one but your translucent cover is what I do too.

    Neil
     
  10. Dr.Longshot

    Dr.Longshot Banned Banned

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    Neil on the Oehler site the Model 84 says that shooting a 2 3/4 inch shell in a 3 inch chamber on a #84 you will se a significant rise in chamber pressure Vs a #71 and confirms what you saw in that 14,000 psi in your testing, and it is explained on the Oehler site.

    The reason is the expansion and and then compression back into the smaller chamber.

    This came out in testing the Nitro 27 loads in a 3 inch chamber and testing in a 2 3/4 inch chamber.

    It also states the significant pressure rise using the #84 in 3 inch chamber.

    Gary
     
  11. Neil Winston

    Neil Winston Well-Known Member

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    I'm sorry, Gary,and I'm not trying to be a pain in the neck, but I just don't see any of that. Please, please, tell me where it is!

    Each screen shot is labeled at the bottom and that will at least make sure we are looking at the same data.

    Really, I can't find any of what you cite. For example, your statement

    "on the Oehler site the Model 84 says that shooting a 2 3/4 inch shell in a 3 inch chamber on a #84 you will se a significant rise in chamber pressure Vs a #71 "

    isn't anywhere I can find. I can't understand it anyway, since the Model 71 _did not measure pressure_. It was a chronograph only. So how can Oehler say that the pressure measurement will be different between the 84 and 71 when _the 71 did not measure pressure_?

    Let's look at the data in the graphic "Test Screen for Comparing Response to Different Shot Materials." Member "870" helped me find proof of my suspicion that traces 7 and 8 were 3 1/2 inch shells since 870 pointed out that it says that below the graphic that shows the pressures and speeds (Test Screen for Comparing Response to Different Shot Materials again.)

    The box in that graphic says the chamber was "only 3 inches" and that's the only reference to chamber length I can find in the whole System 84 website. By the way, the pressure isn't what is written in the "peak" column; it's way, way higher than that. Look at the curves! The flat tops are a warning that the system has passed the top of its measurement range. If it could go higher, it would, by at least a 1000 psi, maybe more. This is a stark warning against using shells in chambers intended for shorter shells.

    Lastly, I can't find any of this either:

    "The reason is the expansion and and then compression back into the smaller chamber.

    This came out in testing the Nitro 27 loads in a 3 inch chamber and testing in a 2 3/4 inch chamber.

    It also states the significant pressure rise using the #84 in 3 inch chamber."

    Is that really there? The second sentence doesn't make any sense to me and the first and third are nowhere I can find.

    So where is it? Exactly? You can copy and past the cited paragraphs and then we can find it. So please, please, copy and paste at least enough that we can understand what you are talking about.

    I hope you aren't just wasting our time, Gary.

    Neil
     
  12. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Neil, I looked also but could only find one reference to a 3" chamber. It was in the display diagrams. I posted the site I was on above.

    If you load that page, scroll all the way to the bottom, the mention is in the second display up from the bottom.

    Initial comparison of different shot material with a M84

    Excess pressures on numbers 7 and 8 were because of a 3 inch chamber.

    That's all I could locate on a 3 inch reading.

    Hap
     
  13. Neil Winston

    Neil Winston Well-Known Member

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    Me too, Hap, thanks.

    I wonder what's going on with Gary that he sees something else.

    Neil
     
  14. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    I know Gary sees pretty good but so do I, still have 20/15 and can't see nothing like I once could!! If he'd list the site addy and page maybe we'd learn something new also?

    Hap
     
  15. Johnny

    Johnny Well-Known Member

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    "The reason is the expansion and and then compression back into the smaller chamber."

    Is that even possible in this case? Sounds like getting something from nothing. Excess pressure wasn't there to begin with. A 2 3/4 in a 3" chamber would be less initial pressure, would it not?
     
  16. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Neil tested the "cut-ringed" shell and the chamber pressures were extremely low! Seems to me it should increase but not according to Neil's pressure gun!

    A 2-3/4 inch shell in a 3 inch chamber should remain the same till the wad column began entering the forcing cone. Seems to me that would somewhat lower the first chamber pressure reading instead of increasing it? How would that work if the forcing cone was removed? The charge would have an extra 1/4 inch to move forward before meeting any cone resistance?

    The quoted explanation above makes no sense to me at all. Back into what smaller chamber, it's the same size till it gets to the forcing cone?

    Hap
     
  17. Johnny

    Johnny Well-Known Member

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    Hap, I assume the "expansion" is taking place in the increased 3 in chamber. And then " compression back into the smaller chamber" is the forcing cone.


    "A 2-3/4 inch shell in a 3 inch chamber should remain the same till the wad column began entering the forcing cone."

    Yes, Hap, that is the way I should have stated it.
     
  18. 870

    870 Well-Known Member

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    Let's just leave it with Neil's questions for Gary to answer and not take it in another direction.

    Either LS can show everyone what he refers to as "first hand information from knowledgable sources and know where to get it" or it's clear he is just making things up.
     
  19. Dr.Longshot

    Dr.Longshot Banned Banned

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    When I googled Oehler Shotshell Testing, there was about 10 options and one ststed that you will get Pressure changes using 2 3/4 inch shells in a 3 inch chamber.

    Neil got a 14,000psi shell reading, was he using a Bbl w/3 inch chamber.

    This was the only specific item that raised my eyebrows.

    Plus wanting to know what model Oehler he was using.

    The Madel #84 says the muzzle is 1.5 foot to the first Coil and 3 ft to the 2nd coil.

    The Royal Canadian Police uses a later model for tests.

    I tried to go back and get that info but the browser does not always take me back so I can down load it.


    Gary Bryant
    Dr.longshot
     
  20. Neil Winston

    Neil Winston Well-Known Member

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    Gary, I don't believe you about "finding it on the net." You made it up, obviously. And we can even determine the thought process that that led you do do so.

    This is where you started:

    "Neil got a 14,000psi shell reading, was he using a Bbl w/3 inch chamber."

    And you got that wrong. I have no idea what made you think my test barrel has a 3-inch chamber but it doesn't. I has a 2 3/4-inch chamber.

    So seeing the high pressure I reported, you decided it must be due to the 3-inch chamber you thought I had and some totally illogical (to everyone else) explanation came to you from who knows where and so you wrote it down claiming it was provided by "knowledgable sources."

    But it wasn't from "knowledgable sources;" it was from you. You made it up and presented it as fact. It is not fact, it is just more of your imagination reported as fact. I'm getting tired of it.

    You can tell all the shooting and grudge-match stories you want. But don't tell people nonsense about top-quality testing equipment and how it works; it just makes you look like a fool.

    Neil
     
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