OCW Load Test, .284 Win.

[Killick]

Trying to conserve my other F-rifle bbl./powder(H4350) so working up a load for Old Blue with a spare jug of H4831sc for 600/1,000 yard club matches. Series 8-55.1gr. is puzzling. It is precisely on the 3% node but jumps up 40fps! from series 7 and careens down 57fps on series 9! I'm tempted to test that load again but the window is so slim it's probably a fool's errand.
Series 1 was a clean bbl. and for some reason the MagnetoSpeed appropriated a shot from series 2...head scratcher.
I deviated from the true OCW process by forgoing the round robin and shot each group consecutively. 3 shots, wait 2 minutes between series.
The node between 53.3 and 53.9 is very promising as the velocity spread is approx. 50 fps (I'm calc'ing the actual Min/Max from the MagSpeed).
Martin

 

[Doom]

So what is more important to you? Trusting in POI of 3 shot groups or the approximate velocity of the 3 rounds?

Group 7 has a 95% confidence Interval of 2782 and 2888. Group 9 is 2769 to 2857. It pretty obvious that these groups are not behaving very well. The rifle seems to like groups 2,3, and 4. That's 9 shots with different charges and almost identical average POI.

Three shots is not enough to tell you much about your true standard deviation. Groups 2,3, and 4 do tell you there is a wide window where you can look for a good SD. Personally, I would pick 53.6 gr. Not because of group size but because it appears to be the middle of a known window. Test it at distance.

 

[David Christian]

If this was my target, I would pursue 53.3 to 53.9. I would also analyze my brass prep as there seems to be a lot of variability in the numbers.

I have found these types of tests to be more valuable when my brass was more consistent.

 

[762plinker]

"I deviated from the true OCW process by forgoing the round robin and shot each group consecutively. 3 shots, wait 2 minutes between series."
what this means in english is you shot THREE SHOT GROUPS...not ocw.
this is how load development was done before and during ladder shooting.

 

[Fast14riot]

You say you used a magneto speed, was it attached to your barrel? If so, you can probably completely discount all those groups. There is nothing more the chrono is telling you at this stage than the target is. You still have to pick a group and test at distance. Knowing ES and SD of 3 rounds is not going to be very meaningful for the next 3 round group. Tune by the target, chrono once done for drops and wind.

If you didn't have the chrono data, you would have looked at group 8 and said it was a half node, unstable. Groups 2-4 is the node. You know it. We know it. Chrono data is only reason you are even curious about group 8. Trust the target! No points for perfect ES or SD in a match!

 

[Doom]

@Killick, on the subject of round robin, it has its purpose and the degree to which it matters depends on the rifle condition (fouling) and ambient conditions (affect on barrel temperature). More critical for lighter sporter barrels.

I glossed over the fact you were using the magnetospeed and that will affect the results. Again more so on a sporter barrel as opposed to a varmint or heavy barrel. You will likely still find the load in that 2,3,4 range.

Keep in mind that a chronograph is an instrument to measure velocity. It tells you what the standard deviation of the data but it does absolutely tells nothing about how to analyze and interpret that information. To do that you need to have an understanding of sampling, probability, and analysis of variance.

 

[762plinker]

@Killick, on the subject of round robin, it has its purpose and the degree to which it matters depends on the rifle condition (fouling) and ambient conditions (affect on barrel temperature). More critical for lighter sporter barrels.

I glossed over the fact you were using the magnetospeed and that will affect the results. Again more so on a sporter barrel as opposed to a varmint or heavy barrel. You will likely still find the load in that 2,3,4 range.

Keep in mind that a chronograph is an instrument to measure velocity. It tells you what the standard deviation of the data but it does absolutely tells nothing about how to analyze and interpret that information. To do that you need to have an understanding of sampling, probability, and analysis of variance.

THREE SHOT groups shot over different conditions will never give enough DATA to produce a standard deviation.
outside of shooting, in the real world sample sizes are massive thousands of data points
in shooting its a nice number, little DATA

 

[big5ifty]

The magnetospeed can potentially change the groups POI, so for that reason alone the test needs repeating.

 

[DLT]

The magnetospeed can potentially change the groups POI, so for that reason alone the test needs repeating.

AMEN

 

[big5ifty]

The magnetospeed can potentially change the groups POI, so for that reason alone the test needs repeating.

Anything called "test" has to be repeatable to be true, so the first result is not gospel, you should follow up with a second test to validate the first.

In OCW tests, to my understanding and what I do, is repeat the test over a narrower charge window around what I think is the node, and check that the group centres are still the same.

And do the test in round-robin fashion. I'm guessing the further you deviate from the way a test is supposed to be done, the less you can rely on it to be a true reflection of said test.

 

[Killick]

Well I think I vindicated my "OCW" load test. Shot this on the 1st string today. Also shot a 200-13x and a 199-8x and won the match with a 599-38x (last shot '9', of course). Next week...1,000 yard match.
Oh, I loaded on the low end, 53.4gr. H4831sc because the forecast was 'HOT' (90⁰). Also, I used Wolf primers instead of my usual S&B's. Love those commie primers.

 

[Killick]

Here's my first target from yesterday, 1st relay of the day at 1,000 yards. 18 shots=8.27"x4.38", 15 shots=Xring elev. Hellacious mirage made the 10/X ring a fuzzy blob (shots 8 & 19), could have been my hold as well. Dropped 12 points but still won the match. I'm officially accepting the success of my renegade OCW project. Next step, perform a 'standard' (vanilla) OCW load test with the loads 1 thru 5 to confirm validity of my apostate OCW method.

 

[CharlieNC]

The "true" OCW test as defined by Dan Newberry is based on the target point of impact, not velocity.

 

[Killick]

Thank you, Gary Eliseo, for this rifle, reborn with a proper load.
Eliseo R1 Prone chassis (Kawasaki Blue) w/Eliseo 'Pickle Forks'
Borden TG (Tube Gun) Action (exclusive to Eliseo chassis)
Benchmark or Brux bbl. (don't remember)
Vortex Golden Eagle scope
custom Doan Trevor pistol grip

 

[Killick]

The "true" OCW test as defined by Dan Newberry is based on the target point of impact, not velocity.

I don't recall mentioning velocity as my goal reference. It's just there for added reference.

 

[CharlieNC]

I don't recall mentioning velocity as my goal reference. It's just there for added reference.

Apparently my confusion........

 

[Doom]

Anything called "test" has to be repeatable to be true, so the first result is not gospel, you should follow up with a second test to validate the first.

In OCW tests, to my understanding and what I do, is repeat the test over a narrower charge window around what I think is the node, and check that the group centres are still the same.

And do the test in round-robin fashion. I'm guessing the further you deviate from the way a test is supposed to be done, the less you can rely on it to be a true reflection of said test.

The OCW method that is documented is set up assuming a clean rifle and to work with any rifle from a 6lb spotter barreled hunting rifle to a heavy barreled rifle of your flavor. Once a shooter knows his rifle it's actually pretty easy to shortcut some of the "official" rules. In particular deviating from round robin is easy to do if you are shooting fouled heavy barrel in moderate temperatures if you know the rifle is consistent. It actually tends to reduce the group sizes since the shooter isn't reestablishing his position for each series. Definitely not a problem for this test.

As for repeatability this is an excellent example of an OCW test and its significance. It doesn't depend on three shots but actually has nine shots on the same point of impact. This test can be repeated and will in all likelihood not reveal much more even if shot at smaller increments. The OP has found his "nodes" and the 3% difference is a good check on the validity of the test. Given the results picking 53.6 gr would be an easy decision. Shooting that load (or another in the 53.3 to 53.9 range) will verify the choice.

The 55.1gr load is an interesting possibility and could be investigated if additional velocity is needed. In that case the load increment can be reduced (I would load 55.1 +/-0.1gr) and see how it shot.

As for the chronograph data, you would expect the velocities to vary about 16 fps for each charge weight and the limited data shows numbers in that range for the range in question. Doesn't mean a lot other than the loads seem reasonable and in the range expected. Reading anything more than that is fruitless since the data is so limited.

 

[Killick]

Thank you, Gary Eliseo, for this rifle, reborn with a proper load.
Eliseo R1 Prone chassis (Kawasaki Blue) w/Eliseo 'Pickle Forks'
Borden TG (Tube Gun) Action (exclusive to Eliseo chassis)
Benchmark or Brux bbl. (don't remember)
Vortex Golden Eagle scope
custom Doan Trevor pistol grip
View attachment 1453198

With Gary's help we determined that it's a Benchmark barrel. Going to order another one today.