Chronograph results from ladder run and SD

[HarryPottar]

Hi,

Once again, newbie getting into reloading.

Got my Dillon all set up with 9mm, finally today I got the chance to shoot my ladder loads with the Chronograph. Unsure about the SD (Sectional Density) readings.

I'm just starting out so I'm not trying to load match quality ammo just yet, looking at loading target ammo.

I first shot some retail 9mm perfecta this averaged 945.2 fps with an SD of 42.5

I then ran my ladder loads and saw averages of 951.7 to 998.3 fps, so happy with that data.

However the heavier the grains the lighter the SD was, the highest I saw was SD: 21.4 the lowest was SD: 11.00 at the max load of 43 grains.

All rounds ran flawlessly but unsure why I got a low SD, even more unsure what it means and should I worry.

Using Titegroup powder, and coper coated 115gr round nose bullets.

thanks

harry

 

[xtry51]

Are you talking about Standard deviation?

The lower the standard deviation, the closer all your rounds were to a common number. It really can be a misleading item to track because what really matters is:

1) accuracy - what are you group sizes for each?
2) pressure signs - are you seeing any?

Also you posted 43grains when what I'm pretty sure you mean is 4.3gr, which is NOT a max load for 115gr Titegroup. Right on the bottle it says 4.8gr for a 115gr 9mm round.

 

[bigblue]

As Xtry already stated, track what matters: point of aim to point of impact. Velocity is going to vary based on so many independent factors that it will drive you crazy. This is why shooters who reload for a specific power factor always give themselves a margin for error. Focus on what really matters.

Oh, and why 115gr? Those velocities are very slow for 115. My 147gr loads are at those velocities.

 

[HarryPottar]

Thanks for the feed back, I'm new so I'm learning as I go.

The SD came from the chronongraph software and I googled it. Yes 4.3 grains, the loading data I'm using from hodgdon Website for 115 grain say 4.3 max. There are no signs of pressure on the cases.

As as a new reloaded I'm concerned with not blowing myself up as I learn but I'm trying to get a round that as enough power to eject but not enough to cause pressure issue on the cases. My first sample 10 rounds I did where light, they ejected fine but had no oomph. So I did a ladder set from 3.9 to 4.3 grains and used the chronograph to get an average fps. As a new shooter the bullets and gun are more accurate than I am.

The data sheet I printed out from the web site states max load 115gr LRN 4.3 gr should produce 1,151 fps. So I under on that.

the 115gr GR GDHP states 4.8gr max but I have the round nose copper plated which I understand is the LRN.

my overall length is 1.1300 the data sheet states 1.100 but seating that low seems to flare the case too much. Should I increase the powder to compensate.

harry

 

[bigblue]

Thanks for the feed back, I'm new so I'm learning as I go.

The SD came from the chronongraph software and I googled it. Yes 4.3 grains, the loading data I'm using from hodgdon Website for 115 grain say 4.3 max. There are no signs of pressure on the cases.

As as a new reloaded I'm concerned with not blowing myself up as I learn but I'm trying to get a round that as enough power to eject but not enough to cause pressure issue on the cases. My first sample 10 rounds I did where light, they ejected fine but had no oomph. So I did a ladder set from 3.9 to 4.3 grains and used the chronograph to get an average fps. As a new shooter the bullets and gun are more accurate than I am.

The data sheet I printed out from the web site states max load 115gr LRN 4.3 gr should produce 1,151 fps. So I under on that.

the 115gr GR GDHP states 4.8gr max but I have the round nose copper plated which I understand is the LRN.

my overall length is 1.1300 the data sheet states 1.100 but seating that low seems to flare the case too much. Should I increase the powder to compensate.

harry

Barrel length will affect your velocity and my guess is they measured using a 5" barrel.

Don't sweat the details so much. I know it's intimidating at first and you don't want to blow anything up. BUT it's 9mm. As long as you don't double charge one, you will be fine.

I aim for a power factor of 130 with 9mm so a 115gr bullet would need to hit 1,130fps. However, if you are simply trying to get reliable function and accuracy then reload for that.

Use those two criteria to measure the success of your reloads NOT standard deviation of velocity (which we already determined is largely irrelevant). $0.02

 

[xtry51]

Knowing the velocity is good for finding out where you are on a starting load. We can see from your velocity (and presumably no pressure signs on brass/primer) that you are way low. That's fine if that's what you want to shoot.

If you want something closer to a factory load, I'd get it above 1100. I load 4.8gr TG for my 115gr Plated Barry's. I've gone up to 5.0 but started to see pressure signs and the recoil gets obnoxious.

In my G34 they get more accurate the faster they go.

 

[EddieCoyle]

my overall length is 1.1300 the data sheet states 1.100 but seating that low seems to flare the case too much.

Harry - Bullet seating should have nothing to do with flaring the cases.

 

[Steve Marshall]

Harry, you might be confusing bulge with flare. Especially in 9MM, dies tend to size a case excessively due to wide variances in 9MM brass and when you seat a bullet you tend to see a bulge.

As to SD, the lower the better. More importantly in pistols would be the ES ( extreme spread ). More important than that would be functioning and accuracy. Higher SD and ES numbers, especially at the distance normally employed by handguns, don't always factor in.

By the way, I went to the Hodgdon site and the start load was 4.5 for Titegroup.

 

[jtnf]

In laymans' terms, Standard Deviation is a measure of variation from the average, and is used TO INDICATE STABILITY OF A FIXED PROCESS. (shouting for emphasis.... the why'll be obvious in a second.)

Starting with the assumption that you have a stable process (i.e. no variables are INTENTIONALLY being changed) SD will tell you just how stable your process is.
In other words, if you are not changing any known variables and your SD is too large, you should start to investigate UNKNOWN VARIABLES.
Since you are running a ladder, SD is absolutely meaningless, as you are intentionally changing the charge weight variable.

An example, in reloading terms:
Loading for rifle, I set up my powder throw for 24.3grn of powder per a loading manual, use tumbled miscellaneous range brass, and the cheapest primers and projectiles I can find.
I find that group size is poor so I spend the coin on a chrony (rather than taking EddieCoyles' precision rifle reloading class ) and find the SD is poor.
Internet research leads me to CASE VOLUME as a variable so I sort cases by headstamp, with a resulting drop in SD and group size.
I then weigh and measure my projectiles and learn that they are from mixed lots and vary slightly in weight and diameter.
Next, I build some rounds with sorted projectiles and note a corresponding reduction group size and SD.
More 'net research leads me to believe that cheap primers may vary in their effect by 50%, whereas "match" primers vary by 20%...
I then take EddieCoyles' class and learn that I should have started with sorted brass and run OCW ladders before chasing SD!


In reality when you get the SD to under a few percent of the total you'll be tilting at windmills.

 

[josh2600]

Harry, you might be confusing bulge with flare.

This. Mine always look really funny compared to factory ammo, esp. if I run .357 stuff. They always go bang.

 

[HarryPottar]

I think you are correct I mean bulge, looks quite odd if I seat them any lower.
I Don't have a good close up shot.



My Barrel length is only 3.25 and the chronograph was 14ft away (measured with a tape measure)

I was surprised at how low the FPS was on the retail 9mm.

Below is a picture of the data I was using.

 

[bill o]

Here's a recipe for a low SD 9mm load: 147 grain Ibejihead bullet, 3.5 g N320, 1.13", mixed brass in a stock G34. My last two chronos at major matches were 910 and 911 fps, with a range of speed within 5 fps (6 shots). I achieved this by arbitrarily picking a load I was pretty sure would make power factor then never changing it.

 

[josh2600]

I think you are correct I mean bulge, looks quite odd if I seat them any lower.
I Don't have a good close up shot.

View attachment 147973

My Barrel length is only 3.25 and the chronograph was 14ft away (measured with a tape measure)

I was surprised at how low the FPS was on the retail 9mm.

Below is a picture of the data I was using.

View attachment 147974View attachment 147975

That's more or less how mine look, like they have a thin waist. If you don't have a case gauge, pull your barrel and just make sure it drops in and out without a problem. Not sure if that method is kosher, but it's all i've ever done and I must be through at least 10k rounds of reloaded 9mm, w/o an issue, by now. Just keep in mind that not all chambers are the same, so make sure you at least use the barrel of the gun you intend to shoot them out of.