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

[Trickymissfit]

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.

I realized that you were using all the screens at the sametime after re-reading your post. Looks like your seeing about .25% just off the top of my head. I wonder what the built in error factor is for each unit? And with a 3600 fps round going thru there will you see a one quarter percent variation? (still less than 10fps). With the screens, I would be more concerned with the direction (s) the screens are pointed at than anything else, yet I think they'd still be good with a five degree variation at the max. Maybe I'm wrong, I don't know. I can tell you that when aligning light curtains (very similar concept), that they had to be pretty close. Still if the screens move from muszzle blast, you will induce a little error that can't be avoided. Your tests are interesting, and I'm following them.
gary

 

[Trickymissfit]

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.

I only know of one importer for Gronenberg cables, and he's in Indianapolis. The Lundberg cables are fairly common and can be bought from Kirby Risk and maybe Mosier. They are wrapped in silver foil with a nice flexable rubber coating. They come in all sorts of lengths, and are often seen with encoders and very low voltage aps. When you buy them they are normally terminated on one end to your specs (they sell about everykind of connector used including DIN couplings). They really shine in discrete applications where there's a lot of interference close by. Another good one is from TPC, and these can be had with about everykind of foil wrap out there.
gary

 

[Pdvdh]

I realized that you were using all the screens at the same time after re-reading your post. Looks like your seeing about .25% just off the top of my head. I wonder what the built in error factor is for each unit? And with a 3600 fps round going thru there will you see a one quarter percent variation? (still less than 10fps). With the screens, I would be more concerned with the direction (s) the screens are pointed at than anything else, yet I think they'd still be good with a five degree variation at the max. Maybe I'm wrong, I don't know. I can tell you that when aligning light curtains (very similar concept), that they had to be pretty close. Still if the screens move from muzzle blast, you will induce a little error that can't be avoided. Your tests are interesting, and I'm following them.
gary

The answer is yes, at MV of 3000 fps. I've been shooting over the Oehler 33 and PACT chronographs in tandem for several years now. The delta of the differences in velocity recorded over those two units is in the low single digits with MVs in the 2900-2950 fps range. So I am confident that the shot to shot precision of the combined units is normally less than 0.25% with MV less than 3000 fps. I have shot some strings in the past where the delta of the differences in recorded velocity is less than 2 fps. Most of the time (well more than 50% of the time) I'm getting deltas of less than 5 fps.

 

[Pdvdh]

I only know of one importer for Gronenberg cables, and he's in Indianapolis. The Lundberg cables are fairly common and can be bought from Kirby Risk and maybe Mosier. They are wrapped in silver foil with a nice flexible rubber coating. They come in all sorts of lengths, and are often seen with encoders and very low voltage apps. When you buy them they are normally terminated on one end to your specs (they sell about every kind of connector used including DIN couplings). They really shine in discrete applications where there's a lot of interference close by. Another good one is from TPC, and these can be had with about every kind of foil wrap out there.
gary

The Oehler Skyscreen III cables are marked with this identification:

C & M Corp AWM Style 2464 80C 300M VW-1 --- LL33361

They seem to do the trick.

 

[Trickymissfit]

The answer is yes, at MV of 3000 fps. I've been shooting over the Oehler 33 and PACT chronographs in tandem for several years now. The delta of the differences in velocity recorded over those two units is in the low single digits with MVs in the 2900-2950 fps range. So I am confident that the shot to shot precision of the combined units is normally less than 0.25% with MV less than 3000 fps. I have shot some strings in the past where the delta of the differences in recorded velocity is less than 2 fps. Most of the time (well more than 50% of the time) I'm getting deltas of less than 5 fps.

actually your results are slightly closer than what Doug and I found when compairing his #35 with the PACT. We would get a variation of about six to eight feet per second. But just as importantly the figures always paralleled each other. I have no idea how you would calibrate either one. Let alone what would you use for a master to go by
gary

 

[Trickymissfit]

The Oehler Skyscreen III cables are marked with this identification:

C & M Corp AWM Style 2464 80C 300M VW-1 --- LL33361

They seem to do the trick.

if they work well for you then so be it. What I'd like is a cable that detaches itself from the screens using a DIN connector (or something else). My big feet are hard on cables!
gary

 

[Pdvdh]

We would get a variation of about six to eight feet per second. But just as importantly the figures always paralleled each other. I have no idea how you would calibrate either one. Let alone what would you use for a master to go by.
gary

When I use the term 'delta of the differences', I am meaning 'paralleled each other'. That's the true reflection of the precision and repeatability of the chronograph setups. In other words, if I were to reset my skyscreen separation distances such that two units provided basically the same velocity (never being sure which velocity is closer to the true actual velocity), and then fired a string of bullets over the chronographs, the maximum difference between the recorded velocities is generally less than 5 fps.

As to determining which velocity of the four recorded velocities I receive from my chronograph setup is closest to the true bullet velocity (the most accurate - closest to the bullseye)? I rely on the three chronographed velocities from the units with the skyscreens with the largest separation distance. I measure and set the skyscreen separation distance as accurately as possible, and then look at the recorded velocities from the three units. In my initial test run using the new skyscreen rail, the two Oehlers with their 6' separation distance and the PACT with its 56" separation distance, were all in very close agreement. So I would average the three velocities, cross my fingers, and conclude that the average of the three is very close to the true bullet velocity. I don't know of any better way to go about it with the tools at my disposal. I don't claim to be able to know the absolute true velocity of my loads. I do claim to be able to determine the ES and SD of my loads to a very high level of accuracy and precision. And my gut feeling is the true bullet velocity isn't very far from the average of the three units.

It would be nice to transport my three units down to Oehler's factory and run them concurrently with one of their $15,000 units, or run them next to a radar set-up. Other than that, averaging the recorded velocity over multiple units is the best idea I've been able to come up with - so that's what I do.

Running multiple chronographs concurrently allows one to quantitatively identify the more reliable chronograph system from the less reliable chronograph system. I keep a running record of all of my shot strings on my PC. This is the process that allows me to state that my Oehler 33 is a more reliable unit with its Skyscreen IIIs - in fading light - than my PACT. Neither the Oehler 33 or the PACT are the current offerings from those two companies. In good lighting, the PACT operates just about as well as the Oehler 33. But I give the Oehler 33 the edge in performance because over the long haul, the ES produced by the Oehler 33 is generally 2-3 fps less than the ES recorded by the PACT. To me, this means the precision of the Oehler 33 is slightly better than the precision coming out of the PACT.

I haven't shot over the Oehler 35P other than the once - and I've posted that date in my initial Post. But over time, I will learn how it compares - performance wise - to the Oehler 33 and PACT.

Paul

 

[Pdvdh]

Another Set of Chronograph Data - For Your Information & Knowledge

Hi guys,

I've been involved in a non-shooting project over the winter and haven't shot or chronographed since last fall. Today I went out and fired a few rounds from my .338 Edge over my triplicate chronograph setup in preparation for a bear hunt. I neglected to bring the skyscreen shades for the Oehler 35P, and when the full sun popped out from behind the clouds, the 35P burped on two shots. Under cloud cover, no problems. The other two chronographs, an Oehler 33 and a PACT PC2, did both have their skyscreen shades mounted overhead. I only chronographed five (5) shots from the 338 Edge. Three (3) under cloud cover that resulted in the collection of good velocity data. Two (2) under full sun that caused some bad data from the Oehler 35P - due to the clear blue sunny sky overhead (no shades over the 35P skyscreens).

I'll provide the 3 rounds that yielded credible data. The first round was a 200 grain Speer bullet that I was using to bore sight the rifle. The next two bullets fired were 265 gr Henson Aluminum Tipped - Rebated Base Boattails.

Oehler 35 Primary 3145 2900 2908 > 6 foot skyscreen spacing
Oehler 35 Proof. . 3152 2906 2918 > 3 foot skyscreen spacing
Oehler 33 . . . . . 3146 2852 2909 > 6 foot skyscreen spacing
PACT PC2 . . . . . 3148 2903 2908 > 56 inch (4' 8") skyscreen spacing

I bolded the 2852 fps from the 2nd shot recorded on my Oehler 33. Obviously the Oehler 33 burped on this 2nd shot and recorded a bogus velocity. But this 3-shot data set illustrates the value of having more than one chronograph recording each and every shot. If I'd only been using the Oehler 33, there would have been no way to know that it provided a value 51 fps slower than the PACT chronograph, 48 fps slower than the 35P primary channel, and 54 fps slower than the 35P proof channel. No way to figure out why the velocity was 48 to 54 feet slower than the velocity that should have been recorded.

After shooting these rounds from my .338 Edge, it was pretty clear that the Proof screens for the Oehler 35P were mounted too close together on my skyscreen rail, since the Proof velocities being recorded were 7, 6, and 10 fps faster than the velocities recorded on the Oehler 35P Primary skyscreen. The Proof skyscreens on the 35P are mounted 1/2 the separation distance of the primary skyscreens, or a 3' spacing. In addition, the 35P Primary channel velocities recorded were a dead match to the Oehler 33 and PACT chronograph data, so I knew the Proof skyscreens needed adjusted - not the Primary skyscreens.

So I came home and got the Ruger .22 semi-auto pistol out and shot in the back yard, in order to adjust the Oehler 35P proof skyscreen separation distance - to yield a Proof channel velocity which would better match the 35P Primary channel velocities. I increased the separation distance between the Proof skyscreens about 1/8". Here's the first 5 shots fired, using a variety of .22LR ammo that I found (pickups from the gun range).

Oehler 35 Primary 1017 1046 1055 939 1038
Oehler 35 Proof. . 1019 1048 1057 940 1040
Oehler 33 . . . . . .1017 1045 1054 938 1037 > My Oehler 33
PACT PC2 . . . . . .1015 1045 1054 938 1037

The 35P Proof channel was still about 2 fps faster than the 35P Primary channel. And the 35P Primary channel velocities were about 1 fps faster than the Oehler 33 and PACT velocities. So I separated the 35P Proof skyscreens about 1/16" farther apart before firing the next five rounds. Next, I conducted a very interesting experiment. I replaced my Oehler 33 chronograph with a different Oehler 33 that I'd purchased from LRH Forum Member 'Alan Griffith' this past December. I'd never used Alan's Oehler 33 before, and I wanted to see if and how it worked, and how the data from Alan's Oehler 33 would compare with the data from my 33 when plugged into the same exact skyscreens. So here's the data from the next five shots.

Oehler 35 Primary 1042 1050 1030 1037 1031
Oehler 35 Proof. . 1043 1052 1031 1037 1032
Oehler 33 . . . . . .1041 1050 1029 1036 1031 > Alan Griffith's Oehler 33
PACT PC2 . . . . . .1041 1050 1029 1036 1031

Dang! Alan's Oehler 33 continued to spit out data exactly matching the data from my PACT PC2. To be honest, I didn't expect to see exactly matching data from this second Oehler 33. After the 3rd of these 5 shots, I again slightly increased the spacing on the 35P Proof skyscreens, and on the 4th shot, you can see that the 35P Proof channel matched the 35P Primary channel velocity at 1037 fps.

Prior to firing the next three shots I increased the spacing of the Oehler 35P Primary skyscreens slightly. The Oehler 33s and the PACT PC2 had recorded the exact same velocities for the past 9 shots fired. I wanted to see if I could get the 35P Primary channel to read 1fps slower to bring it into agreement with the two Oehler 33s and the PACT chronographs. Next three shots:

Oehler 35 Primary 920 1055 1079
Oehler 35 Proof. . 919 1054 1079
Oehler 33 . . . . . .920 1054 1078 > Alan's Oehler 33
PACT PC2 . . . . . .920 1054 1078

At this point the Oehler 33 and the PACT PC2 chronographs had recorded the same exact velocity for the prior 12 shots. Pretty remarkable! I fired three more rounds just to see how long this string of matching velocities would last. Here's the data from the last three shots fired:

Oehler 35 Primary 1072 1031 969
Oehler 35 Proof. . 1073 1030 969
Oehler 33 . . . . . .1071 1030 968 > Alan's Oehler 33
PACT PC2 . . . . . 1072 1026 969

As you can seen, the string of duplicate data from the Oehler 33 and the PACT chronographs stopped at 12 consecutive shots. The PACT chronograph produced a slightly errant value (1026 fps) on the second of these last three shots. Not a gross error, but 4 fps slower than the Oehler 33 and 35P Proof channel. All three chronographs are yielding data that more or less match one another with my current skyscreen spacings.

Quite a few times over the years, I've read Posts that pooh poohed the value of chronograph data for purposes of determining muzzle velocity. Some even claim measuring bullet drops over extended ranges is a better method of determining muzzle velocity. I clearly disagree with that camp of shooters. After reviewing the quality and consistency of the above data, y'all can make up your own mind on that topic. I do believe a shooter needs to have at least a tandem chronograph setup - two recorded velocity data for each bullet fired - in order to place high confidence in the data. Either for purposes of identifying the ES and SD of one's loads. Or for purposes of entering valid muzzle velocities in a ballistics program, such as LoadBase 3 or Exbal.

Hope this presentation of data is clear enough that you're all able to understand/interpret the data. Feel free to ask questions, if necessary. It was fun to get out and shoot and do a little more chronographing.

Good shoot'in!

 

[Trickymissfit]

Re: Another Set of Chronograph Data - For Your Information & Knowledge

Hi guys,

I've been involved in a non-shooting project over the winter and haven't shot or chronographed since last fall. Today I went out and fired a few rounds from my .338 Edge over my triplicate chronograph setup in preparation for a bear hunt. I neglected to bring the skyscreen shades for the Oehler 35P, and when the full sun popped out from behind the clouds, the 35P burped on two shots. Under cloud cover, no problems. The other two chronographs, an Oehler 33 and a PACT PC2, did both have their skyscreen shades mounted overhead. I only chronographed five (5) shots from the 338 Edge. Three (3) under cloud cover that resulted in the collection of good velocity data. Two (2) under full sun that caused some bad data from the Oehler 35P - due to the clear blue sunny sky overhead (no shades over the 35P skyscreens).

I'll provide the 3 rounds that yielded credible data. The first round was a 200 grain Speer bullet that I was using to bore sight the rifle. The next two bullets fired were 265 gr Henson Aluminum Tipped - Rebated Base Boattails.

Oehler 35 Primary 3145 2900 2908 > 6 foot skyscreen spacing
Oehler 35 Proof. . 3152 2906 2918 > 3 foot skyscreen spacing
Oehler 33 . . . . . 3146 2852 2909 > 6 foot skyscreen spacing
PACT PC2 . . . . . 3148 2903 2908 > 56 inch (4' 8") skyscreen spacing

I bolded the 2852 fps from the 2nd shot recorded on my Oehler 33. Obviously the Oehler 33 burped on this 2nd shot and recorded a bogus velocity. But this 3-shot data set illustrates the value of having more than one chronograph recording each and every shot. If I'd only been using the Oehler 33, there would have been no way to know that it provided a value 51 fps slower than the PACT chronograph, 48 fps slower than the 35P primary channel, and 54 fps slower than the 35P proof channel. No way to figure out why the velocity was 48 to 54 feet slower than the velocity that should have been recorded.

After shooting these rounds from my .338 Edge, it was pretty clear that the Proof screens for the Oehler 35P were mounted too close together on my skyscreen rail, since the Proof velocities being recorded were 7, 6, and 10 fps faster than the velocities recorded on the Oehler 35P Primary skyscreen. The Proof skyscreens on the 35P are mounted 1/2 the separation distance of the primary skyscreens, or a 3' spacing. In addition, the 35P Primary channel velocities recorded were a dead match to the Oehler 33 and PACT chronograph data, so I knew the Proof skyscreens needed adjusted - not the Primary skyscreens.

So I came home and got the Ruger .22 semi-auto pistol out and shot in the back yard, in order to adjust the Oehler 35P proof skyscreen separation distance - to yield a Proof channel velocity which would better match the 35P Primary channel velocities. I increased the separation distance between the Proof skyscreens about 1/8". Here's the first 5 shots fired, using a variety of .22LR ammo that I found (pickups from the gun range).

Oehler 35 Primary 1017 1046 1055 939 1038
Oehler 35 Proof. . 1019 1048 1057 940 1040
Oehler 33 . . . . . .1017 1045 1054 938 1037 > My Oehler 33
PACT PC2 . . . . . .1015 1045 1054 938 1037

The 35P Proof channel was still about 2 fps faster than the 35P Primary channel. And the 35P Primary channel velocities were about 1 fps faster than the Oehler 33 and PACT velocities. So I separated the 35P Proof skyscreens about 1/16" farther apart before firing the next five rounds. Next, I conducted a very interesting experiment. I replaced my Oehler 33 chronograph with a different Oehler 33 that I'd purchased from LRH Forum Member 'Alan Griffith' this past December. I'd never used Alan's Oehler 33 before, and I wanted to see if and how it worked, and how the data from Alan's Oehler 33 would compare with the data from my 33 when plugged into the same exact skyscreens. So here's the data from the next five shots.

Oehler 35 Primary 1042 1050 1030 1037 1031
Oehler 35 Proof. . 1043 1052 1031 1037 1032
Oehler 33 . . . . . .1041 1050 1029 1036 1031 > Alan Griffith's Oehler 33
PACT PC2 . . . . . .1041 1050 1029 1036 1031

Dang! Alan's Oehler 33 continued to spit out data exactly matching the data from my PACT PC2. To be honest, I didn't expect to see exactly matching data from this second Oehler 33. After the 3rd of these 5 shots, I again slightly increased the spacing on the 35P Proof skyscreens, and on the 4th shot, you can see that the 35P Proof channel matched the 35P Primary channel velocity at 1037 fps.

Prior to firing the next three shots I increased the spacing of the Oehler 35P Primary skyscreens slightly. The Oehler 33s and the PACT PC2 had recorded the exact same velocities for the past 9 shots fired. I wanted to see if I could get the 35P Primary channel to read 1fps slower to bring it into agreement with the two Oehler 33s and the PACT chronographs. Next three shots:

Oehler 35 Primary 920 1055 1079
Oehler 35 Proof. . 919 1054 1079
Oehler 33 . . . . . .920 1054 1078 > Alan's Oehler 33
PACT PC2 . . . . . .920 1054 1078

At this point the Oehler 33 and the PACT PC2 chronographs had recorded the same exact velocity for the prior 12 shots. Pretty remarkable! I fired three more rounds just to see how long this string of matching velocities would last. Here's the data from the last three shots fired:

Oehler 35 Primary 1072 1031 969
Oehler 35 Proof. . 1073 1030 969
Oehler 33 . . . . . .1071 1030 968 > Alan's Oehler 33
PACT PC2 . . . . . 1072 1026 969

As you can seen, the string of duplicate data from the Oehler 33 and the PACT chronographs stopped at 12 consecutive shots. The PACT chronograph produced a slightly errant value (1026 fps) on the second of these last three shots. Not a gross error, but 4 fps slower than the Oehler 33 and 35P Proof channel. All three chronographs are yielding data that more or less match with my current skyscreen spacings.

Quite a few times over the years, I've read Posts that pooh poohed the value of chronograph data for purposes of determining muzzle velocity. Some even claim measuring bullet drops over extended ranges is a better method of determining muzzle velocity. I clearly disagree with that camp of shooters. After reviewing the quality and consistency of the above data, y'all can make up your own mind on that topic. I do believe a shooter needs to have at least a tandem chronograph setup - two recorded velocity data for each bullet fired - in order to place high confidence in the data. Either for purposes of identifying the ES and SD of one's loads. Or for purposes of entering valid muzzle velocities in a ballistics program, such as LoadBase 3 or Exbal.

Hope this presentation of data is clear enough that you're all able to understand/interpret the data. Feel free to ask questions, if necessary. It was fun to get out and shoot and do a little more chronographing.

Good shoot'in!

you did well! The one thing I picked up right away was the consistencey from chronograph to chronograph per shot. The error with the first shot string is extremely small between all of the chronographs, and in the top of my head it looks to be in the .00023% area (maybe all wrong so don't shoot me yet). I get this from the 7fps variation; which is about seven tenths of a percent at 1000fps. Divid that by three for 3150fps (average)

excellent work son!
gary

 

[Pdvdh]

Re: Are Chronographs Accurate and Reliable?

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 'elkaholic' 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.

. . . . . . .33 . . . . 35Primary . . . PACT . . 35Proof
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. elkaholic has definitely figured out how to manufacture very accurate bullets!

 

[royinidaho]

Well done!!!

 

[Mikecr]

Awesome information
THANK YOU

 

[Trickymissfit]

the differences between all the units is nil at best. But I gotta ask you one question; I see that you have the screens setup at 34 feet from the muzzel. Any particular reason why?
gary

 

[bigngreen]

Good stuff man!! Could I send a couple cronies to ya for independent testing