New Oehler 35P, New skyscreen rail, First Test Data

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by phorwath, Sep 6, 2010.

  1. phorwath

    phorwath Well-Known Member

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    Received my new 2010 production Oehler 35P about 2 weeks ago. I also have an Oehler 33 and PACT PC2 chronographs which I've run in tandem the past several years. I wanted to run all three chronographs concurrently by mounting all 7 skyscreens on a single rail. I was having difficulty converting my original skyscreen rail so I decided to purchase $35.00 worth of aluminum material from the local Steel supply retailer and welded together a new skyscreen rail as illustrated in the following photos:

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    Materials:
    5' 4" of 2"x2"x1/8" angle aluminum
    6' 8" of 5/8" solid aluminum rod
    4 aluminum braces cut out of 1/8" scrap angle aluminum and two end protectors from 1/8" thick aluminum plate obtained from my neighbor's bone-yard.

    The 2"x2"x1/8" angle aluminum is drilled and tapped for mounting to a standard camera tripod. After welding, the rail was spray painted with dull red primer paint to prevent glints of sun reflection from a shiny rail to the undersides of the bullets while passing over the skyscreens. I then carefully measured for separation distance and mounted the 7 skyscreen rails.

    The Oehler 35P primary channel skyscreen spacing is 6'. Proof channel @ 3' spacing. The Oehler 33 spacing is also 6'. All Oehler skyscreens are mounted on the 5/8" solid aluminum rod. The PACT PC2 skyscreen spacing is 4' 8". The PACT skyscreens mount on a flat surface, so they're mounted on two of the aluminum angle braces. The two end plates protect the skyscreens from the lumps and bumps associated with transportation and also serve to protect the skyscreens from muzzle blast.

    Here are the data from the first string of 8 shots fired:
    Oehler 35P1 1212 1222 1210 1217 1186 1177 1210 1204
    Oehler 33... 1210 1221 1211 1220 1188 1179 1212 1206
    PACT PC2... 1213 1222 1208 1216 1183 1175 1208 1202

    Oehler 35P2 1216 1226 1212 1220 1188 1179 1211 1203
    The 4th row of data are the 35P Proof data collected over the 3' skyscreen spacing. However I was tweaking the separation distance of the middle 'Proof' skyscreen during the first 5 shots to best match the 6'-spaced primary skyscreen data. The last three shots were taken with no additional changes to the Proof channel skyscreen position, and the maximum difference between the primary and proof channel data for these last three shots was 2fps.

    The first 4 shots were from a semi-auto rifle chambered for 9mm pistol ammo. The last 4 shots were 22 long rifle from a bolt action rifle.

    With this setup, I'll now obtain four velocity data for each shot fired. This will generate relatively high confidence in my MVs and down-range velocities. It should now be relatively easy to ID which unit throws a bad number when that happens. And that does happen every now and then with any chronograph.
     
    Last edited: Sep 7, 2010
  2. jmden

    jmden Well-Known Member

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    All I can say is 'wow'. That is impressive. It will be very interesting to follow your continued testing and shooting in the field to see how it all comes together. Nice work!
     

  3. J E Custom

    J E Custom Well-Known Member

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    Very slick set up.

    That rig should give you some very accurate information.

    Keep us posted on the performance of all of the chronographs. Looks like the old 33
    still works good.

    J E CUSTOM
     
  4. dave7mm

    dave7mm Well-Known Member

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    Well I finally know of someone other than myself thats still running a Model 33.

    dave
     
  5. Boss Hoss

    Boss Hoss Well-Known Member

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    THANK YOU!!! You are the man for doing this!!!!!!!!!!!

    LEN---make this a sticky!!!!!!!!!!
     
  6. bigbuck

    bigbuck Well-Known Member

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    If things go wrong and you shoot one of the chronies then you've shot all three :D (just pokin)

    very nice set up and good job !

    BigBuck
     
  7. Chas1

    Chas1 Well-Known Member

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    phorwath, great setup, creatively done. Any thoughts about putting all the cables into like a cable harness type of setup?
     
  8. phorwath

    phorwath Well-Known Member

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    I did harness the cables for the three units, but separately; three Oehler cables for the 35P, 2 cables on the Oehler 33, and the two cables for the PACT. That's a good idea, and a nice improvement when it comes time to setup the different cables to the different units.

    The Oehler cables are well insulated from electrical noise. Not so sure about the PACT. PACT tech staff have told me in the past to try to keep their skyscreen cables separated while running from the skyscreens to their unit. This is the first time I've bundled those cables together. If I start having problems with the PACT, I may have to separate those two cables.
     
  9. Chas1

    Chas1 Well-Known Member

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    Let us know if you start having any problems.
     
  10. Trickymissfit

    Trickymissfit Well-Known Member

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    the light bar for a PACT PC2 is 24" from the factory. Did you check the aluminum bar to see how strait it was when you set it up? That's a problem everybody I know that bought a 35 runs into. And with three screens; what are all those extra cables for?

    secondly I assume you did unplug the other two chronographs when firing the data. Otherwise the other two units will probably interfer with the one in use
    gary
     
    Last edited: Oct 17, 2010
  11. Trickymissfit

    Trickymissfit Well-Known Member

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    It's a good idea to always keep the cables for any photo cell or light screen seperate from the others. You can fix some of this down the road by going to Lundberg cables all the way around as they are better insulated than the factory stuff. I may build a set of Gronenberg cables to see what happens as they have the best isolation of any wire manufactured (would cost about $50 for enough cable), and I have about thirty feet gathering dust. Try wrapping the exteriors in copper foil tape as an experiment if you think your seeing interference between the cables.
    gary
     
  12. phorwath

    phorwath Well-Known Member

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    Gary,
    The extra cables in the photograph are the cables from the 7 different skyscreens I have mounted on my skyscreen rail. I wasn't shooting at the time of the photos. I simply draped the cables over the skyscreen rail while I was taking photographs to post in this Thread. There should be a total of 7 skyscreen cables. Three for the Oehler 35P, two for the Oehler 33, and two for the PACT.

    Absolutely not!. All three units run and record velocity for each and every bullet fired - concurrently. This is the real value in running chronographs in tandem or triplicate. Two, three, or in my case, four sets of recorded data are collected for each bullet fired. This provides the additional data required in order to validate the quality of the data. There wouldn't be any good reason to shoot over mutliple chronographs if only one of them was used at any one time. I wouldn't bother purchase and setting up multiple units is I could only fire over them one at a time. Getting multiple velocities for each bullet fired is what it's all about.

    As you can see from the data, no troubles or interference recording data with the cables plastic tied together. I recently corresponded with another Forum member from Colorado. He's running his skysreen cables for his Oehler 35P in one bundle and getting about 2-3fps differences between his primary and proof channel over a 6' long skyscreen separation distance with his 338 Lapua Improved. His ES is running less than 10 fps for his final loads. So with that kind of quality data, he's obviously not experiencing any problems with electrical interference.

    I talked to Ken Oehler and his wife at the 2009 Shot Show in Orlando, Florida. They told me their current Skyscreen III units are better insulated compared to their prior generation skyscreens. He told me that the PACT skyscreen cables should not interfere with the Oehler skyscreen cables or operation. But I didn't ask either of them if they recommended bundling Oehler Skyscreen III generation cables together, or if that would be problematic.

    Supporting your comments though, the PACT technician I talked with about 4-5 years ago via telephone told me that their skyscreen cables should be kept separated. I've always done that my PACT until I set up my new Oehler 35P on this newly constructed (homemade) skyscreen rail. I've only shot the initial bullets over it that I posted data for earlier in this thread. So far - so good. But I appreciate your observations and comments, and I will keep that in mind if the PACT starts to act up.

    I never even used the Oehler-provided 4'-long piece of EMT skyscreen rail that was shipped out with their 35P, so I haven't really inspected it for straightness. The first bullets I fired over the 35P were over my homemade 6' 8"-long skyscreen rail. Also, I've never used any PACT provided skyscreen rail. I prefer to shoot over skyscreens separated over a 5 to 6 foot distance, in order to reduce the error associated with slightly inaccurate skyscreen separation distances.
     
    Last edited: Oct 17, 2010
  13. phorwath

    phorwath Well-Known Member

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    If I experience any troubles, I may send you a PM to inquire about these cables. I don't know what brand skyscreen cables Oehler is currently using. But there is some writing stamped on their cables. I'll take a look and see if the brand name of their Skyscreen III cable is legible.
     
  14. phorwath

    phorwath Well-Known Member

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    Will do. I haven't fired any more bullets over my new skyscreen rail yet. Alaskan hunting seasons opened and I was out and about. Our hunting seasons are largely over now, so... pretty soon I'll be throw lead over the chronographs again.

    Have you received your 35P yet? I think you will be pleased. They're a bit costy compared to some other brands and options, but you have to include consideration of the fact that you're actually getting the equivalent of TWO chronographs, because you obtain the second reading from the 35P PROOF channel. A second reading is invaluable!

    Plus there is no other brand name as well recognized in the world, synonymous with chronographs, than Oehler. As the saying goes - They know chronographs inside and out. They produce the commercial grade units used where the utmost in accuracy and reliability, is required. That's what they were busy doing all those years when they had halted production of their consumer grade 35P. Specializing in the production of the high-end grade, commercial chronographs units. The ones I can't afford to purchase... :)