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Huge Velocity Deviation 9mm Major


Kevrend
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Starting to develop my first 9major load. Currently using 124gr Extreme Copper Plated RN bullets, CCI500, mixed brass, VV N340 6.8gr, OAL 1.160. Runs reliably and good return to zero, but when I chronographed it the other night, i was getting huge jumps from 1375fps (which was my goal velocity) down to 1050ish with nothing in between. My gut reaction was that the chrono wasn’t reading accurately, but is it common to have such a huge deviation? I could understand something like 50fps but 300fps? Gun is a Dan Wesson Havok open pistol. 

Edited by Kevrend
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A few things to consider - plated bullets don't work well at major PF velocities.  That doesn't exactly explain your velocity issue but you may have accuracy issues.  Did you chrony in low light conditions?  If its not the chrony and environment, are you possibly losing powder out of the case?  At 6.8 gr of N340, you should have plenty of room in the case but losing powder is one way where you can have inconsistent velocity.

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13 minutes ago, Balakay said:

This amount of deviation is way too high. Check your powder drops. Are they consistent?  Is the powder bar resetting completely?

^^^This, and can you feel the difference? That much drop should be pretty noticeable in recoil and sound. If there’s no perceived difference I’d double check the chrono. 

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There can be several explanations of the huge difference.  First would be improper chrono technique.  The bullet path must be along the long axis of the chrono and parallel to the sensor ports.  Any deviation from that path results in lower velocities, sometimes by a surprising amount.  You need a rest and a target.  Put the bullets into the same hole and you'll get more accurate results.  If you also send them on the correct flight path you'll get the most accurate readings.

 

Second, your choice of bullets is poor. X-Treme bullets are quite inconsistent.  So much so that I refused to buy any even when they were the only ones available.  You would be better off using a 124 JHP.  Not only are the weights too variable, OALs with them are inconsistent.  Save them for minor steel challenge loads.

 

Third is your choice of powder.  N340 is, IMO, too fast for 9mm major and It does not fill the case properly.  That leads to variations.  I really cannot explain it other than to say that when I was developing loads, SDs got better as the powder got slower.

 

Fourth, you are using a Dillon powder measure, and you got a sloppy one.

 

It may be a combination of one or more of the above.  FWIW, if a major load does not return consistent SDs in the single digit range, I scrap it.  My current 9mm major load returns SDs between 4.9 and 5.5 for 10 and 15 shot strings every time I test.

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Another possibility is X-treme bullets are very shiny. That can cause erratic readings.  I have been told and have tried coloring the bullet with black magic marker.  I did not get big swings using this method. My powder for the test was VV N350. I also don't load for major PF and have not had any issues with the bullets. I used to use Montana Gold 115 gr. CMJ but haven't been able to get for over a year so I quit using them.

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1 hour ago, mstewart said:

Another possibility is X-treme bullets are very shiny. That can cause erratic readings.  I have been told and have tried coloring the bullet with black magic marker.  I did not get big swings using this method. My powder for the test was VV N350. I also don't load for major PF and have not had any issues with the bullets. I used to use Montana Gold 115 gr. CMJ but haven't been able to get for over a year so I quit using them.

This.
 

For some reason when I used plated bullets years ago I could never get a traditional chrono to consistently read correctly.

 

I would imagine if you were actually getting that big of a swing you’d see other signs. Noise, feel, POI shift.

 

When I chrono plated bullets with my labradar they read fine.

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N340 is not the powder you want for 9major.  Did you check for over pressure signs? Trying to make 170Pf with N340 you have to be at the edge.  Get some N350, 3N37,3N38 or Major pistol powder

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8 hours ago, CZ85Combat said:

N340 is not the powder you want for 9major.  Did you check for over pressure signs? Trying to make 170Pf with N340 you have to be at the edge.  Get some N350, 3N37,3N38 or Major pistol powder

But 340 does work in 38 super. I know some guys that run it

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On 6/14/2021 at 9:08 AM, Furrly said:

Have you tried chronying other rounds you made with the same press.. Process of elimination.?? 

I chrono'ed two minor power factor loads from the same press, using the same powder and brass. One of which was also the copper plated bullets, one was coated bullets. The coated bullets got single digit SD readings, which leads me to believe that maybe the chronograph wasn't picking up the copper plated bullets accurately.

 

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On 6/14/2021 at 1:52 PM, iflyskyhigh said:

This.
 

For some reason when I used plated bullets years ago I could never get a traditional chrono to consistently read correctly.

 

I would imagine if you were actually getting that big of a swing you’d see other signs. Noise, feel, POI shift.

 

When I chrono plated bullets with my labradar they read fine.

There's zero felt shift in recoil, sound, flash. Is there a better recommendation for bullets for the comp'ed guns? I knew to steer clear of coated bullets and bullets with exposed lead at the rear, so I assumed copper plated was the way to go. And perhaps I should just dive in and purchase a Labradar.

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4 minutes ago, Kevrend said:

There's zero felt shift in recoil, sound, flash. Is there a better recommendation for bullets for the comp'ed guns?

MG JHP OR CMJ bullets

PD JHP

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1 hour ago, Kevrend said:

I chrono'ed two minor power factor loads from the same press, using the same powder and brass. One of which was also the copper plated bullets, one was coated bullets. The coated bullets got single digit SD readings, which leads me to believe that maybe the chronograph wasn't picking up the copper plated bullets accurately.

 

Never been a Fan of Plated bullets !!! 

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You can safely use heavy plate bullets rated for 1500fps in Open.  I don't see why you would, because they cost the same or more than JHPs.

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On 6/14/2021 at 1:52 PM, iflyskyhigh said:

This.
 

For some reason when I used plated bullets years ago I could never get a traditional chrono to consistently read correctly.

 

I would imagine if you were actually getting that big of a swing you’d see other signs. Noise, feel, POI shift.

 

When I chrono plated bullets with my labradar they read fine.

I've had similar problems chrono'ng plated bullets, too shiny.

Edited by Postal Bob
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On 6/15/2021 at 2:07 PM, CZ85Combat said:

N340 is not the powder you want for 9major.  Did you check for over pressure signs? Trying to make 170Pf with N340 you have to be at the edge.  Get some N350, 3N37,3N38 or Major pistol powder

It can be done with N340, similar to WSF for 9 major. 

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On 6/14/2021 at 8:50 AM, mstewart said:

Another possibility is X-treme bullets are very shiny. That can cause erratic readings.  I have been told and have tried coloring the bullet with black magic marker.  I did not get big swings using this method. My powder for the test was VV N350. I also don't load for major PF and have not had any issues with the bullets. I used to use Montana Gold 115 gr. CMJ but haven't been able to get for over a year so I quit using them.

I’ve run into this before too, black sharpie works when the glint is too much for chrono screens. 

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Just now, HoMiE said:

I’ve run into this before too, black sharpie works when the glint is too much for chrono screens. 

 

H and similar posters:  if you have a problem chronoing shiny bullets your chrono position is wrong.  You have direct sunlight hitting the chrono and in particular the sensing ports.  That is a no no.  The chrono should be completely in the shade with the sky screens open to the sky.  That, and shooting directly down the long axis of the chrono parallel to the sensing ports is the ONLY way to get accurate results.  Better yet, do it in the shade and use an IR light kit.

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8 hours ago, zzt said:

 

H and similar posters:  if you have a problem chronoing shiny bullets your chrono position is wrong.  You have direct sunlight hitting the chrono and in particular the sensing ports.  That is a no no.  The chrono should be completely in the shade with the sky screens open to the sky.  That, and shooting directly down the long axis of the chrono parallel to the sensing ports is the ONLY way to get accurate results.  Better yet, do it in the shade and use an IR light kit.

Not always possible in Southern Oregon.  One range has no shade so your at mercy of cloud cover. I’ve tried to put a white target on top of screens. Sometimes it works. 

 

Only other thing that I’ve seen cause big variation is bullet set back but that usually make rounds way too fast. 

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20 hours ago, zzt said:

 

H and similar posters:  if you have a problem chronoing shiny bullets your chrono position is wrong.  You have direct sunlight hitting the chrono and in particular the sensing ports.  That is a no no.  The chrono should be completely in the shade with the sky screens open to the sky.  That, and shooting directly down the long axis of the chrono parallel to the sensing ports is the ONLY way to get accurate results.  Better yet, do it in the shade and use an IR light kit.

Not saying you’re wrong, but when I was using the old chrono I couldn’t get plated bullets to read. Then shot FMJs and JHPs in the exact same conditions, minutes later, and gotten correct consist readings.

 

I used two different chronos in the AZ desert sun for years before I got my lab radar with little issue (except for plated). 

 

So you are probably correct that traditional chronos work best in the conditions you described, and maybe the chrono can read plated in perfect conditions, but how often to we get that scenario?

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