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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
New Oehler 35P, New skyscreen rail, First Test Data
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<blockquote data-quote="Pdvdh" data-source="post: 516741" data-attributes="member: 4191"><p><strong>Re: Are Chronographs Accurate and Reliable?</strong></p><p></p><p>I finally fired a few higher velocity rounds over these chronographs. The setup provides four velocities for each bullet fired. I was testing some 190 gr VLD-style bullets manufactured by Rich (user name '<strong>elkaholic</strong>' on this Forum). Firing these bullets from a 25.5" long Lilja 10.5 twist barrel. The first skyscreen was located 34 feet from the muzzle. I run an Oehler 33, an Oehler 35P, and a PACT PC2 in triplicate. The Oehler 35P provides two velocity recordings. One from the Primary Channel and one from the Proof Channel. The Primary Channel is the more accurate of the two because the skyscreens are spaced precisely twice as far apart as the Proof Channel skyscreens.</p><p></p><p>For those of you that are into chronographs and chronographing, or anyone else that has always wondered if chronographs can produce reliable velocity data, here's how my three units performed for six consecutive rounds fired. The first two shots were loaded with 80gr H1000. The next two shots were 81gr H1000. The last two shots were loaded with 82gr H1000.</p><p></p><p> . . . . . . .<u><strong>33</strong></u> . . . . <u><strong>35Primary</strong></u> . . . <u><strong>PACT</strong></u> . . <u><strong>35Proof</strong></u></p><p>80gr. . . 2977fps . . . 2981fps. . . . 2981fps . 2976fps . . Maximum difference = 5fps</p><p>80gr. . . 3033 . . . . . 3034 . . . . . .3031 . . . 3032 . . . . Maximum difference = 3fps</p><p></p><p>81gr. . . 3048 . . . . . 3051 . . . . . .3048 . . . 3048 . . . . Maximum difference = 3fps</p><p>81gr. . . 3054 . . . . . 3057 . . . . . .3055 . . . 3054 . . . . Maximum difference = 3fps</p><p></p><p>82gr. . . 3061 . . . . . 3064 . . . . . .3062 . . . 3062 . . . . Maximum difference = 3fps</p><p>82gr. . . 3064 . . . . . 3066 . . . . . .3064 . . . 3066 . . . . Maximum difference = 2fps</p><p></p><p>In each of these six shots, it can be seen that the Oehler 35P Primary Channel provided the highest velocity. If I increase the Primary skyscreen spacing on the Oehler 35P ever so slightly, then the 35P Primary velocities could be tweaked down into more or less perfect agreement with the other three velocities for an even closer match. Neglecting the 35P Primary Channel velocities in this string of six shots would reduce the Maximum velocity difference between the remaining three recorded velocities to 5 fps, 1 fps, 1 fps, 1 fps, 1 fps, and 2 fps.</p><p></p><p>If the environmental conditions, or any other factors were 'fooling' these three chronographs, or the 7 associated skyscreens, then it was 'fooling' them all equally. I see no evidence to support the common expressed opinion that a fella can't trust his chronograph velocity data, with this type of chronograph setup. If I had only been running one chronograph, then I couldn't have known whether or not the difference in velocity between the first two rounds fired with 80gr H1000 was good data or bad data. The ES on the first two shots was 50-56fps, depending on which chronograph data is used. The ES on the following two sets of shots was much less; 6 fps and 3 fps, respectively. With all four chronographs providing very similar data, I know with virtual certainty that velocity data recorded for all six shots is valid, and that the 80 grain charge isn't a keeper for long range application. 80 grains must not produce high enough pressure for efficient/consistent combustion of the gunpowder.</p><p></p><p>By the way, these three 2-shot groups were fired onto a target at 308 yards, and the equivalent group sizes in "inches per 100 yards" were 0.43", 0.38", and 0.28". The first two shots with the largest velocity spread produced the largest group. The last two shots with the smallest extreme spread produced the smallest group. I'm not saying that happens all the time, let alone most of the time. Just making the observation that it did with these three 2-shot groups.</p><p></p><p>Another observation: These are the first three loads I've tested with these Sherman SXR 190gr Aluminum-Tipped bullets, and these are about the best three groups my fairly lightweight custom rifle has ever fired. My rifle has a #4 contour Lilja barrel, which typically requires more load development to find a sweet load combination compared to a rifle with a #7 or #8 contour barrel. And I've spent a lot of time testing any number of different bullets with a variety of different powders, powder charges, and seating depths. <u><strong>elkaholic</strong> has definitely figured out how to manufacture very accurate bullets</u>!</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 516741, member: 4191"] [b]Re: Are Chronographs Accurate and Reliable?[/b] I finally fired a few higher velocity rounds over these chronographs. The setup provides four velocities for each bullet fired. I was testing some 190 gr VLD-style bullets manufactured by Rich (user name '[B]elkaholic[/B]' on this Forum). Firing these bullets from a 25.5" long Lilja 10.5 twist barrel. The first skyscreen was located 34 feet from the muzzle. I run an Oehler 33, an Oehler 35P, and a PACT PC2 in triplicate. The Oehler 35P provides two velocity recordings. One from the Primary Channel and one from the Proof Channel. The Primary Channel is the more accurate of the two because the skyscreens are spaced precisely twice as far apart as the Proof Channel skyscreens. For those of you that are into chronographs and chronographing, or anyone else that has always wondered if chronographs can produce reliable velocity data, here's how my three units performed for six consecutive rounds fired. The first two shots were loaded with 80gr H1000. The next two shots were 81gr H1000. The last two shots were loaded with 82gr H1000. . . . . . . .[U][B]33[/B][/U] . . . . [U][B]35Primary[/B][/U] . . . [U][B]PACT[/B][/U] . . [U][B]35Proof[/B][/U] 80gr. . . 2977fps . . . 2981fps. . . . 2981fps . 2976fps . . Maximum difference = 5fps 80gr. . . 3033 . . . . . 3034 . . . . . .3031 . . . 3032 . . . . Maximum difference = 3fps 81gr. . . 3048 . . . . . 3051 . . . . . .3048 . . . 3048 . . . . Maximum difference = 3fps 81gr. . . 3054 . . . . . 3057 . . . . . .3055 . . . 3054 . . . . Maximum difference = 3fps 82gr. . . 3061 . . . . . 3064 . . . . . .3062 . . . 3062 . . . . Maximum difference = 3fps 82gr. . . 3064 . . . . . 3066 . . . . . .3064 . . . 3066 . . . . Maximum difference = 2fps In each of these six shots, it can be seen that the Oehler 35P Primary Channel provided the highest velocity. If I increase the Primary skyscreen spacing on the Oehler 35P ever so slightly, then the 35P Primary velocities could be tweaked down into more or less perfect agreement with the other three velocities for an even closer match. Neglecting the 35P Primary Channel velocities in this string of six shots would reduce the Maximum velocity difference between the remaining three recorded velocities to 5 fps, 1 fps, 1 fps, 1 fps, 1 fps, and 2 fps. If the environmental conditions, or any other factors were 'fooling' these three chronographs, or the 7 associated skyscreens, then it was 'fooling' them all equally. I see no evidence to support the common expressed opinion that a fella can't trust his chronograph velocity data, with this type of chronograph setup. If I had only been running one chronograph, then I couldn't have known whether or not the difference in velocity between the first two rounds fired with 80gr H1000 was good data or bad data. The ES on the first two shots was 50-56fps, depending on which chronograph data is used. The ES on the following two sets of shots was much less; 6 fps and 3 fps, respectively. With all four chronographs providing very similar data, I know with virtual certainty that velocity data recorded for all six shots is valid, and that the 80 grain charge isn't a keeper for long range application. 80 grains must not produce high enough pressure for efficient/consistent combustion of the gunpowder. By the way, these three 2-shot groups were fired onto a target at 308 yards, and the equivalent group sizes in "inches per 100 yards" were 0.43", 0.38", and 0.28". The first two shots with the largest velocity spread produced the largest group. The last two shots with the smallest extreme spread produced the smallest group. I'm not saying that happens all the time, let alone most of the time. Just making the observation that it did with these three 2-shot groups. Another observation: These are the first three loads I've tested with these Sherman SXR 190gr Aluminum-Tipped bullets, and these are about the best three groups my fairly lightweight custom rifle has ever fired. My rifle has a #4 contour Lilja barrel, which typically requires more load development to find a sweet load combination compared to a rifle with a #7 or #8 contour barrel. And I've spent a lot of time testing any number of different bullets with a variety of different powders, powder charges, and seating depths. [U][B]elkaholic[/B] has definitely figured out how to manufacture very accurate bullets[/U]! [/QUOTE]
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New Oehler 35P, New skyscreen rail, First Test Data
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