Velocity question

Hartblood · May 12, 2013, 09:52 AM

I have made two loads for my 40 the only differance is the powder charge. The first one is 8.2 grains with a variance of powder drop +/- .2 grains. The second is 8.6 grains with a variance of powder drop +/- .1 grains.

The velocity averages for five rounds fired are:
First load is 973.
Second load is 852.

Powder: Accur #7
Primer: CCI

So my question is why am I seeing lower velocity with a higher charge?

I.R.Chevy · May 12, 2013, 10:45 AM

There are more other things that attribute to velocity other than powder charge. Could be brass resizing or bullet seating not being the same as the previous load. Also your scale may need a cal? I'm by no means a pro but I would look at your consistency.

Brian Pfleuger · May 12, 2013, 10:48 AM

Chronograph error. How far is your muzzle from the chrony?

Jimro · May 12, 2013, 10:49 AM

Where did you set the chrono? Sounds like a classic case of being too close to me.

Jimro

Hartblood · May 12, 2013, 04:25 PM

How far should the chrono be out? I don't what to shoot it.

Brian Pfleuger · May 12, 2013, 04:31 PM

15 feet is the standard.

Hartblood · May 12, 2013, 04:54 PM

Well it was closer then that. I will move it farther out at next range time.

Brian Pfleuger · May 12, 2013, 06:36 PM

The loads you list could be almost identical... 8.2+0.2, 8.6-0.1, only 0.1gr apart.

Other than that, no way should a 5% charge increase result in 150fps lower velocity.

Chrony distances less than 15 can cause errors because the sensors are seeing the muzzle blast instead of the bullets. Anything less than 8-10 feet is very likely to cause errors with most centerfire handgun cartridges.

My 357sig with a 5.3" barrel will literally rock the chrony from 5 feet or so. Very nearly tips it over.

steve4102 · May 12, 2013, 08:17 PM

What bullet and bullet weight were you using?

Hartblood · May 12, 2013, 08:46 PM

165 grain flat nose FMJ.

Ruger45LC · May 14, 2013, 10:25 AM

I am always at least 10ft from the chronograph, plus you have to make sure it's level, the rods aren't bent and you're in good lighting. On top of that run some test loads through there to verify you're in the right ball park before you start testing handloads. I've seen instances where more powder does equal less velocity, but not by 120 fps, so something is off.

WESHOOT2 · May 15, 2013, 09:58 PM

Quote:

no way should a 5% charge increase result in 150fps lower velocity.

More time developing and testing will teach you that is entirely possible.
Just not expected....

Brian Pfleuger · May 15, 2013, 10:22 PM

Maybe "possible" but HIGHLY unlikely, particularly in a handgun cartridge. We're talking about a 20% drop in speed. It's not like 150 fps off 3,500.

WESHOOT2 · May 16, 2013, 05:37 AM

Ditto "highly unlikely".

I have spent a bit of time chronographing, and I learned to repeat-test same-lot ammo repeatedly.
Sometimes over years.....

May 12, 2013, 09:52 AM	#1
Hartblood Member Join Date: May 11, 2013 Posts: 28	Velocity question I have made two loads for my 40 the only differance is the powder charge. The first one is 8.2 grains with a variance of powder drop +/- .2 grains. The second is 8.6 grains with a variance of powder drop +/- .1 grains. The velocity averages for five rounds fired are: First load is 973. Second load is 852. Powder: Accur #7 Primer: CCI So my question is why am I seeing lower velocity with a higher charge?

May 12, 2013, 10:45 AM	#2
I.R.Chevy Member Join Date: March 2, 2013 Location: Little Smoky, AB Posts: 23	There are more other things that attribute to velocity other than powder charge. Could be brass resizing or bullet seating not being the same as the previous load. Also your scale may need a cal? I'm by no means a pro but I would look at your consistency. __________________ Pin it to Win it.

May 12, 2013, 10:49 AM	#4
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	Where did you set the chrono? Sounds like a classic case of being too close to me. Jimro __________________ Machine guns are awesome until you have to carry one.

May 12, 2013, 06:36 PM	#8
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	The loads you list could be almost identical... 8.2+0.2, 8.6-0.1, only 0.1gr apart. Other than that, no way should a 5% charge increase result in 150fps lower velocity. Chrony distances less than 15 can cause errors because the sensors are seeing the muzzle blast instead of the bullets. Anything less than 8-10 feet is very likely to cause errors with most centerfire handgun cartridges. My 357sig with a 5.3" barrel will literally rock the chrony from 5 feet or so. Very nearly tips it over. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

May 12, 2013, 08:46 PM	#10
Hartblood Member Join Date: May 11, 2013 Posts: 28	165 grain flat nose FMJ. Last edited by Hartblood; May 12, 2013 at 08:51 PM.

May 12, 2013, 10:48 AM	#3
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	Chronograph error. How far is your muzzle from the chrony?

May 12, 2013, 04:25 PM	#5
Hartblood Member Join Date: May 11, 2013 Posts: 28	How far should the chrono be out? I don't what to shoot it.

May 12, 2013, 04:31 PM	#6
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	15 feet is the standard.

May 12, 2013, 04:54 PM	#7
Hartblood Member Join Date: May 11, 2013 Posts: 28	Well it was closer then that. I will move it farther out at next range time.

May 12, 2013, 08:17 PM	#9
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,952	What bullet and bullet weight were you using?

May 14, 2013, 10:25 AM	#11
Ruger45LC Senior Member Join Date: July 24, 2005 Location: Kentucky Posts: 768	I am always at least 10ft from the chronograph, plus you have to make sure it's level, the rods aren't bent and you're in good lighting. On top of that run some test loads through there to verify you're in the right ball park before you start testing handloads. I've seen instances where more powder does equal less velocity, but not by 120 fps, so something is off.

May 15, 2013, 10:22 PM	#13
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	Maybe "possible" but HIGHLY unlikely, particularly in a handgun cartridge. We're talking about a 20% drop in speed. It's not like 150 fps off 3,500. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

May 16, 2013, 05:37 AM	#14
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	"landscaping with lead" Ditto "highly unlikely". I have spent a bit of time chronographing, and I learned to repeat-test same-lot ammo repeatedly. Sometimes over years..... __________________ . "all my ammo is mostly retired factory ammo"

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