Sharpie method on ladder test, MV Issues??

[Nomad909]

For anyone that HAS experience in this, I could really use your help, I'm out of ideas

Long story short.. I used the "sharpie method" of marking the projecticle to identify them at distance for a ladder test. Prior to the that I did an ocw test, the results are in the pic on the left page (disregard charge 30.7)

I then shot a ladder test @475 yards, the results are on the right.. looking at the comparable charges of 30.6~~31.4

(OCW first------- ladder after)
Min @ 30.6 went from- 2849 to 2803

Max @31.4 went from 2893 to 2855

In all identical charge weights from 30.6, 30.8, 31, 31.2, 31.4 the OCW shot prior to the ladder test was faster..

The ES is very similar in both circumstances and an almost exact parallel shift down in mv of roughly 50ish FPS.
View attachment 7714560
As a disclaimer, all the following are the same lot:
Berger 105s
Alpha OCD virgin
Cci 450s
Varget (newer lot, just opened)

I never took the chrono off my gun, the shots were taken in the exact same conditions less than 20mins apart. To the best of my ability, NOTHING CHANGED. The only thing I did was sharpie the projecticles... is it possible that the sharpie alone is the culprit of a 50fps drop in MV??

I have every intention of recreating this scenario as best that I can but until then I'm reaching out in hopes that someone can share any insight that might help.

 

[Wheres-Waldo]

I've used the sharpie method in the past and while I didn't see a velocity shift, I didn't get color on the target like you have there, and abandoned it.

Question.... Was there sharpie on the bearing surface of the bullet, and if yes, do you think that may play a part in what you're seeing?

 

[Nomad909]

Yes it was on the bearing surface. I've found the color is much more pronounced that way.

I'm not sure if that's the cause or not.. I have a hard time believing that but it's quite literally the ONLY thing I changed

 

[supercorndogs]

I only see a ladder test. Where is the OCW test?

 

[Wheres-Waldo]

I only see a ladder test. Where is the OCW test?

In the spiral bound notes.

@Nomad909
Maybe a 10X string of whatever compared to the same 10X plus a sharpie would shed some light on it.

 

[spife7980]

In the spiral bound notes.

That’s not an ocw test.

 

[Wheres-Waldo]

A powder charge/velocity node test actually, not an OCW... And the ladder test as stated is closer to an OCW than a ladder.

Either way, what causes the population velocity swing?

 

[LR1845]

I've used the sharpie method in the past and while I didn't see a velocity shift, I didn't get color on the target like you have there, and abandoned it.

Question.... Was there sharpie on the bearing surface of the bullet, and if yes, do you think that may play a part in what you're seeing?

a Q-tip with rubbing alcohol lightly dab around the holes will bring the colors out.

 

[supercorndogs]

The ladder test is not close to an OCW. OCW is specific method based on a specific theory. An OCW specifically uses 100y to remove variables such as MV, and wind.

 

[Wheres-Waldo]

@supercorndogs

I stand corrected on the OCW.

 

[Nomad909]

The ladder test is not close to an OCW. OCW is specific method based on a specific theory. An OCW specifically uses 100y to remove variables such as MV, and wind.

I'm aware of Dan Newberry's method and what an ocw test was, I measured POI from center and round Robin looking for a consistent harmonic lull. That's not at all the purpose of this thread. The groups from the OCW are irrelevant.. I'm strictly referring to the chrono readings hence why I excluded the groups.

Does sharpie act like some kind of lubricant and is it possible that it's effecting MV?

 

[OREGUN]

Jepeers. This is classic Hide. OP asks a question and within 3 posts there’s an irrelevant side argument, over semantics, that derails the whole thread. Next, I predict that some well meaning know-it-all amateur statistician will weigh in that the sample size is too small and all data are meaningless.

OP: I’m having trouble sorting your data. Are the ES numbers there somewhere? Yes, the sharpied rounds slowed down some…and I see your SDs but a look at the ES would give you some idea of where the sharpied speeds lie in relation to the range established by the ES.

MY GUESS: it’s has more to do with the system heating up than with the sharpie on the bullets. The 13 rounds in the card are enough to warm up the barrel, let alone however many were shot for the data in the notebook. In 20 mins, that’s a bunch.

I’ve never shot the sharpie test with the chrony attached….because I never found it that helpful (the test itself) and quit doing it.

I like the looks of your speeds around 30.9-31.1. What chambering, I may have missed it?

also, things will settle down some once the brass is once-fired.

 

[CNC-Dude]

When you watch slow mo videos of guns being shot, a large column of flame exits the barrel long before the bullet comes out of the barrel. Since the bullet is likely fully engulfed in a fire inside the chamber and barrel before it exits, I would think the Sharpie residue would be burned off long before it could influence the bullet in any way....

 

[Nomad909]

Jepeers. This is classic Hide. OP asks a question and within 3 posts there’s an irrelevant side argument, over semantics, that derails the whole thread. Next, I predict that some well meaning know-it-all amateur statistician will weigh in that the sample size is too small and all data are meaningless.

OP: I’m having trouble sorting your data. Are the ES numbers there somewhere? Yes, the sharpied rounds slowed down some…and I see your SDs but a look at the ES would give you some idea of where the sharpied speeds lie in relation to the range established by the ES.

MY GUESS: it’s has more to do with the system heating up than with the sharpie on the bullets. The 13 rounds in the card are enough to warm up the barrel, let alone however many were shot for the data in the notebook. In 20 mins, that’s a bunch.

I’ve never shot the sharpie test with the chrony attached….because I never found it that helpful (the test itself) and quit doing it.

I like the looks of your speeds around 30.9-31.1. What chambering, I may have missed it?

also, things will settle down some once the brass is once-fired.

Appreciate the response/support

It's a 6dasher .273 neck .135 fb

And the 13 shots were over 20 mins but I didn't let them cook in the chamber at all and my mv speeds when shooting PRS never, ever deviate that much... even on 12 shot strings in 120sec, especially with varget.

I apologize the data is a little sloppy due to the conditions and time constraints and I will make a more legible copy. But, the ES I was referring too is strictly my min~max in both the grouping/chrono/ocw/wtf it identifies as, test vs my ladder @475

OCW Min 30.6 @ 2849
Max 31.4 @ 2893
(es from min-max 54fps)
Ladder Min 30.6 @ 2803
31.4 @ 2855
(Es from min to max 52)

My main correlation was that is was almost an exact 53ish FPS drop with identical everything (minus the sharpie). Which leads me to believe I either had a chronograph issue which I've never had (magnetto v3 on a gray ops arca) or it has to be the sharpie...

 

[Seymour Fish]

Appreciate the response/support

It's a 6dasher .273 neck .135 fb

And the 13 shots were over 20 mins but I didn't let them cook in the chamber at all and my mv speeds when shooting PRS never, ever deviate that much... even on 12 shot strings in 120sec, especially with varget.

I apologize the data is a little sloppy due to the conditions and time constraints and I will make a more legible copy. But, the ES I was referring too is strictly my min~max in both the grouping/chrono/ocw/wtf it identifies as, test vs my ladder @475

OCW Min 30.6 @ 2849
Max 31.4 @ 2893
(es from min-max 54fps)
Ladder Min 30.6 @ 2803
31.4 @ 2855
(Es from min to max 52)

My main correlation was that is was almost an exact 53ish FPS drop with identical everything (minus the sharpie). Which leads me to believe I either had a chronograph issue which I've never had (magnetto v3 on a gray ops arca) or it has to be the sharpie...

Clean bbl. foul it, run a few non-sharpies to confirm

 

[Nomad909]

@Seymour Fish that's my intention of course. I'm just curious if I'm the only person that's ever experienced this.

Reached out to buddy that I know uses/used to use this method.. guess I'm not the only one..

 

[Wheres-Waldo]

 

[supercorndogs]

Do the colored markers and black both do it?

 

[OREGUN]

Now I’m just curious. How does less friction slow the round down?

 

[Wheres-Waldo]

Now I’m just curious. How does less friction slow the round down?

Same way molybdenum, HBN and others slow the round down. Less friction = less pressure = less velocity

 

[OREGUN]

Oh. Duh.

 

[spife7980]

Ive never noticed the shift myself. And going back digging through my records I find some that agree with your hypothesis that marker slows it down and also some that dont because the marker is going faster.
But its always been a different weekend between the two events and not straight up marker vs non marker.

Guess I have a test to do myself in a couple weekends when I can get back to it on the bench. God, I hope that I cant prove it one way or another because its so damn convenient to have the holes colored.

 

[supercorndogs]

How much of the bullet was colored?