Strange 9mm major chrono results

[Pro2AInPA]

How far from the muzzle are you putting the chronograph?

Indoors or out?

If indoors, what's the light source?

10 ft. Outdoors. Tried the IR screen and normal shades with natural light (in the shade on a sunny late afternoon).

[Nik Habicht]

Gotta do it with once fired, same head stamp to get reasonable ES and SD values.

Cases from different manufacturers have different volumes.

Bummer. Cheap/free brass WAS a major benefit of 9 major.

It could still be, but you'd have to sort it and potentially work up different loads...

[Xfactor]

Dave, I've had really consistent results with my Shooting Chrony. My test results matched-up well with those of the CED M2s at Nat'ls.

Mixed head stamp will yield a bit more variation, but it shouldn't be a huge difference. You could test some loads of all the same head stamp to see if that's the culprit. (If so, you could always sort your mixed brass to pick out your favorite head stamp, then test it separately to get a baseline with just that head stamp, and save them for use at major matches... )

[Pro2AInPA]

Thanks guys. I'll see what headstamp I have the most of and load 100 or so with it and see if I get consistent results. If not . .. it may be time for a new chronograph. I really love the way this load feels in this gun, and would hate to make any drastic changes.

[Erik S.]

Could be that you were in the shade. I wouldn't set the chrono in the shade UNLESS you're using your IR kit. Since you have an IR kit, I'm beginning to think it's not the chrono unless there's something wrong with a sensor or the main unit.

FWIW. Keep us posted on what you find out! I think the biggest thing at this point would be to put those SAME loads through a friend's chrono and see if they match your results...if not, it's your chrono.

[Pro2AInPA]

Could be that you were in the shade. I wouldn't set the chrono in the shade UNLESS you're using your IR kit. Since you have an IR kit, I'm beginning to think it's not the chrono unless there's something wrong with a sensor or the main unit.

FWIW. Keep us posted on what you find out! I think the biggest thing at this point would be to put those SAME loads through a friend's chrono and see if they match your results...if not, it's your chrono.

A good friend has a Pro Chrono Digital. I'll see if we can get together so I can try it out. Man this is frustrating. Major matches starting in a little over a month and instead of focusing on practicing I'm worried about making PF.

[lcs]

FWIW----I don't believe different headstamps will contribute to the variations you are seeing.

[Pro2AInPA]

FWIW----I don't believe different headstamps will contribute to the variations you are seeing.

I was kind of doubting it too. At this point I really think it's just a crappy chronograph.

[lcs]

How far from the muzzle are you putting the chronograph?

Indoors or out?

If indoors, what's the light source?

10 ft. Outdoors. Tried the IR screen and normal shades with natural light (in the shade on a sunny late afternoon).

Chrono should NOT be in the shade and sun is at to great an angle late afternoon. The chrono god will mess with your readings .

[Pro2AInPA]

How far from the muzzle are you putting the chronograph?

Indoors or out?

If indoors, what's the light source?

10 ft. Outdoors. Tried the IR screen and normal shades with natural light (in the shade on a sunny late afternoon).

Chrono should NOT be in the shade and sun is at to great an angle late afternoon. The chrono god will mess with your readings .

So the sun should be overhead. . . like around noon?

Edited to add: When using the IR screens, the position of the sun should have no effect, right?

Edited March 29, 2011 by Pro2AInPA

[edwin garcia]

Chrono set-up recommendations from one of the manufacturer's manual:

"If the projectile is too bright or shiny, or if a strong reflection is cast off the

ground, "glints" can occur. The reflection of light illuminated onto the bottom

of the bullet prevents the sensors from reading it. Try using a black marker to

paint the shiny surface of the bullet black. Also, make sure that the ground

under the chronograph does not cast a strong reflection back up onto the

chronograph. Conditions such as snow or water on the ground can cause such

a reflection.

In some cases when the sunlight reflects directly off shiny bullets, erratic

recordings can occur. Try positioning a sun screen so that the bullet while

passing over the sensors is in a shaded area.

Inadequate Lighting or too much light can cause problems. In the case of too

much light, try relocating the chronograph into an area that provides more shade

from direct sunlight, but does not create inconsistent shade over the sensors

themselves."

[Aircooled6racer]

Hello: If it is accurate and it makes major what is the problem? Thanks, Eric

[Pro2AInPA]

Hello: If it is accurate and it makes major what is the problem? Thanks, Eric

Take a look at those strings. If my chrono is correct, there are multiple shots in each string that don't make major. If the chrono man ends up with THOSE rounds .. I'm getting scored minor, since they don't chrono 10 round strings at matches.

[Hi-Power Jack]

Hello: If it is accurate and it makes major what is the problem? Thanks, Eric

Take a look at those strings. If my chrono is correct, there are multiple shots in each string that don't make major. If the chrono man ends up with THOSE rounds .. I'm getting scored minor, since they don't chrono 10 round strings at matches.

Exactly. That's why most of us don't shoot for 165 or 167 pf,

but try for 172+ pf.

If I fire 20 shots thru the Chrony, I don't want ANY of them to be

below 166. Which means I'm averaging 172-175.

The chrono man can select any three rounds he wants:))

[Pro2AInPA]

Hello: If it is accurate and it makes major what is the problem? Thanks, Eric

Take a look at those strings. If my chrono is correct, there are multiple shots in each string that don't make major. If the chrono man ends up with THOSE rounds .. I'm getting scored minor, since they don't chrono 10 round strings at matches.

Exactly. That's why most of us don't shoot for 165 or 167 pf,

but try for 172+ pf.

If I fire 20 shots thru the Chrony, I don't want ANY of them to be

below 166. Which means I'm averaging 172-175.

The chrono man can select any three rounds he wants:))

And that is my goal! I'm just not totally comfortable loading well above what other shooters shooting similar guns/loads are using. I know multiple people making 170pf average with this load in 5" guns. It doesn't make sense that with a new barrel, I would need to load more powder than them. Because of this, I'm having a hard time trusting my chronograph.

Edited March 29, 2011 by Pro2AInPA

[Foxbat]

Well, if the question is - "How much can mixed brass affect your results, worst case?", then the answer is: Nobody knows, as nobody has ever tried all possible kinds.

The reality is, you are working with at least three variables, actually more like four. You have volume variations, weight fluctuations, depth variances and also bullet shape imperfections.

A .1gr difference in weight, not detectable by most scales, will easily shift the PF by 2-5 points. There are always going to be depth tolerances also.

As far as bullets are concerned, I have seen differences of up to 1/2 of one thousandth of an inch, for the same lot of MG bullets. This is understandable, as bullets in the same lot come from different dies, I suspect.

Taken all this into consideration, you reduce the variables you can. Keeping your seating die clean will improve the depth repeatability, as will keeping the bullet straight before you seat it. Did you measure COL of every round? What was the spread?

As far as brass - most people agree that you should use single stamp, preferably same lot, for major matches. Get a box of Winchester ammo, shoot it and use its brass for repeatability test - or just buy a small lot of Starline for this test, just to eliminate this particular variable. Otherwise you might end up chasing a ghost forever.

A chrono is always a suspect, so chaining it with another is a good test.

Edited March 29, 2011 by Foxbat

[Erik S.]

Yep, alot of good responses and suggestions here. Thanks for posting back often to answer the questions posed to you. That helps everyone determine what you have/haven't tried.

If your chrono mounts on a standard tripod (not familiar with your chrono), pick up a tripod that has a head tilt feature (sideways!, not just the handle forward and back). If you're shooting in the AM or PM, or anytime, you can angle the head to tilt your chrono at the perfect angle to the sun. Stick a dowel through the "shooting area" and make sure a nice shadow is cast across both sensor openings. If your tilt is too drastic, you will have a smaller shooting area, so don't shoot your chrono, but with pistol that's not usually an issue. With rifle, you have to consider your sight height (height difference between your bore line and sight line).

[JAFO]

I know this isn't exactly apples to apples, since I load minor for production, but my last test of HS-6 before I switched to Titegroup gave me the following:

Temp: 65 oF

Sky: Clear

Distance from muzzle to first screen: ~15'

Gun: Sig P226, 4.4" factory barrel

Primer: Fed #100 Small Pistol

Bullet: 124gr Zero FMJ (Avg wt of 10 bullets pulled from the same box was 124.7gr. I used this weight for the PF calculation.)

COL: 1.161"

Mixed range brass

All strings were made up of 20 shots

Load 1 (6.7gr HS-6):

HI: 1147 / LO: 1082 / AV: 1120 / ES: 65 / Sd: 13 / Power Factor: 139

I used a ProChrono Digital for the velocity measurements.

[Hannu]

You do not need rifle primer to ignite HS-6, I usually get lower deviation with regular pistol primer with HS-6.

Bullet friction to brass has very big effect on what will be the velocity deviation and when you chrono definitely use only same brass. It means, same brand / lot but also you need to have brass that has been loaded for example 3 times - not so that some brass is loaded 2 times and some of the brass 8 times. It can have even bigger effect on velocities than brass brand.

Other thing might be rough barrel bore. I have never got consistent velocities with my Schuemann barrel that has very rough bore. KKM with smooth bore shoots 10 shots of the same load with less than 20 fps max deviation when Schuemann has at least 2x more.

My CED M2 only works reliably when screens are in a shadow. Direct sunlight from any direction - strange readings sometimes (like 300 fps off) and does not measure all bullets.

[CocoBolo]

Try a new battery in the Crono.

[Pro2AInPA]

Thanks a ton for all the help guys. Is the general consensus that I should use the IR screens at all times, regardless of lighting?

[Hi-Power Jack]

Thanks a ton for all the help guys. Is the general consensus that I should use the IR screens at all times, regardless of lighting?

Sounds like you've pretty much decided that this is a chrono problem.

A lot of people have responded with alternatives to that - you should

change the battery on your chrono, and check it against another chrono,

but there are a bunch of other options - your chrono may be fine.

It might be one of a half dozen other problems, most of which will be

solved by adding .2 or .3 grains of powder, slowly, checking for

velocity and pressure.

Just a thought ...

Hope you get back to us with the end results of all this testing.

[Pro2AInPA]

Thanks a ton for all the help guys. Is the general consensus that I should use the IR screens at all times, regardless of lighting?

Sounds like you've pretty much decided that this is a chrono problem.

A lot of people have responded with alternatives to that - you should

change the battery on your chrono, and check it against another chrono,

but there are a bunch of other options - your chrono may be fine.

It might be one of a half dozen other problems, most of which will be

solved by adding .2 or .3 grains of powder, slowly, checking for

velocity and pressure.

Just a thought ...

Hope you get back to us with the end results of all this testing.

I'm going to try a longer OAL and matching headstamp brass for my next test. To throw a wrench into the gears, Montana Gold has the 124gr JHPs backordered, so I'll be switching to CMJs for the next test batch.

The question was just basically - for the next time I go to test . .. use the IR screens?

[yoshidaex]

Just keep things consistent.

At this point you're changing so many things you won't know what the culprit is.

[lcs]

Hello: If it is accurate and it makes major what is the problem? Thanks, Eric

Take a look at those strings. If my chrono is correct, there are multiple shots in each string that don't make major. If the chrono man ends up with THOSE rounds .. I'm getting scored minor, since they don't chrono 10 round strings at matches.

Exactly. That's why most of us don't shoot for 165 or 167 pf,

but try for 172+ pf.

If I fire 20 shots thru the Chrony, I don't want ANY of them to be

below 166. Which means I'm averaging 172-175.

The chrono man can select any three rounds he wants:))

And that is my goal! I'm just not totally comfortable loading well above what other shooters shooting similar guns/loads are using. I know multiple people making 170pf average with this load in 5" guns. It doesn't make sense that with a new barrel, I would need to load more powder than them. Because of this, I'm having a hard time trusting my chronograph.

Barrels can definitely produce different results even from the same manufacturer. Your right to question your chrono results. You have a large spread of low FPS and high FPS. I would be trying to validate my chrono also.