First Post - Help with chrono results

[muncie21]

Perhaps a bit off-topic...what's the purpose/function of the white plastic 'screw' on the top of your powder slide?

[Wobbly]

The "small" sliding powder bar is half the size of the "large" powder bar. So with the small powder bar, there is a stationary spacer plate on top of the slider. The white nylon button holds the stationary plate in place.

Now, back to our regularly scheduled thread.

 

[ptouchton]

Okay round #2...complete adjustment to process using the suggestions....loaded up a ladder and back to the range with the chrono today. I am still stumped with the results....the numbers look better and I really like the 10 drop average method. Below is my numbers from today. I was so disappointed that I went out and bought another scale just to double check my scale...I was fully convinced along with you guys that I have more powder than I think. Alas, the new scale verified that the first scale seems okay.....my quest continues

CZ  P09 9mm
Berry's 124gr hbrn
win brass
wssp priers
c.o.l: 1.14

I shot 8 rounds of remington 115gr mc I had laying around for a control group to test the chrono. Suggested fps from their site said 1145 fps......and my chrono had the average at 1144 so, i feel like i set the chrono up okay....level and it was cloudy @ 7:30 am so I didn't shade the chrono.

grains   10 drop avg    avg. vel.      ES   SD    +/-
-------   -------------    ---------       ---   ---     ---
4          39.7                 1019        44    17   
4.1        41.0                 1034       44    17    15
4.2        41.9                 1051       62    20    17
4.3        43.2                 1076       25      8    25

I came home recorded these numbers in the log and went back to the garage and created a new ladder with a c.o.l at 1.15. I guess I just really want to see numbers closer to the published load. I really feel like I have been really diligent with powder charge now and thought these would be better.

[IDescribe]

FIRST RUN:

3.9gr |   971 ft/s | ES-47 | SD-19
4.0gr | 1004 ft/s | ES-50 | SD-18 | +33
4.1gr | 1046 ft/s | ES-26 | SD-10 | +42

SECOND RUN:

4.0gr | 1019 ft/s | ES-44 | SD-17
4.1gr | 1034 ft/s | ES-44 | SD-17 | +15
4.2gr | 1051 ft/s | ES-62 | SD-20 | +17
4.3gr | 1076 ft/s | ES-25 | SD-08 | +25

I came home recorded these numbers in the log and went back to the garage and created a new ladder with a c.o.l at 1.15. I guess I just really want to see numbers closer to the published load. I really feel like I have been really diligent with powder charge now and thought these would be better.

Well, you can forget that business of your data matching the load data.    It happens sometimes.  It doesn't happen others.  It should NOT be a benchmark. 

As to your being diligent and effective with measuring powder charges, I believe you are.  Look at your velocity progression : +15, +17, +25.  That's fine.  And that bigger bump and significant drop in ES and SD at 4.3 all point to your getting a good seal and an efficient burn at that point.  And if you're loading this for 9mm minor, 1076 is a comfortable spot in terms of velocity, as well.   Don't change your OAL.  There's nothing wrong going on here.

[ptouchton]

Really!?!?...I guess in this quest I understood that our numbers are usually under published numbers because of the test gun...etc. And I thought that once I hit max velocity I am done....given that it is our only "guestimate" of pressure?

I did like the progression in the ladder...eveything felt more uniform...I just wished it would have been 35-50 fps slower....

[IDescribe]

124gr bullets with W231/HP38 is a common combination for action shooting sports in 9mm minor, and your velocities are in line with what I and other people get.  I can't tell you exactly what I get with YOUR combo because I don't shoot plated, but you're line with what I get with jacketed and with what others get with both jacketed and plated -- within a window a few tenths wide.

4.3gr-4.5gr  with a 124gr plated or jacketed bullet is very common with power factors from 130 - 135 depending on bullet and pistol.  You're looking at a PF of 133.4 with 4.3gr.  Is that a little more velocity than average for 4.3gr?  Yes, probably a little, but not enough to make an issue of.  Don't sweat it.  You're in good company. 

Also, to be clear from my last post, when I said the load data shouldn't be used as a benchmark, I intended that your data matching the published data shouldn't be used as a benchmark to grade your success or your method.  Obviously, it's a benchmark in other ways.

[ptouchton]

Thanks Idescribe...I really appreciate the insights from this post and I unserstand now what you mean about the benchmark comment. Thanks again for the help!

[1SOW]

One other thing:  MOST load data "Barrel Lengths"  are usually 4".  How long is your CZ bbl.?  That will result in more velocity when everything else is equal.

Also the Load data isn't really out of a pistol.  It's out of a test machine with pressure transducers and other stuff. 

[ptouchton]

1SOW it is a 4 1/2 barrel in a P09.....Is there a general FPS expectation with different barrel lengths? For example if a 4" barrel is producing 1000 FPS....would you add 10% for a 4 1/2" barrel expecting 1100?  I have read older posts where you guys say the test guns are different than ours....but, do you guys factor different barrels in for expectations?

I get that 4.3-4.5 seems to be the range for 124 HBRN and 231 for minor power factor....and I guess that is why I was surprised when I started hitting max around 4.1. So, for the reloading experience...If I am at 1076 which is 39 fps above published max...I am okay because of the ability to run +P loads?

Also, would I be better served to switch to WSF and work up to minor from a slower powder....to be in a more "middle range" of a bullet/powder combo?

Sorry for all of the questions...It will gel for me at some point...

[1SOW]

My opinions only:   The speed will be higher with a longer bbl. than the load data recorded in the data.
 My experience with a hotter load,  gave me about a 30-40 fps gain with a CZ 75 4.63" bbl..

Personally,  I would run with the 231/HP38 tests and find out how it shoots for you in your pistols.  Record the data.
You may be very happy with what you find.
After that then you can start over again with a new (maybe slower) powder and have a better idea of what to expect.

Or Not.  Reloading can be fun.

[IDescribe]

Is there a general FPS expectation with different barrel lengths?....would you add 10% for a 4 1/2" barrel expecting 1100?  I have read older posts where you guys say the test guns are different than ours....but, do you guys factor different barrels in for expectations?

With any reasonable load in a pistol with a barrel of any reasonable pistol length, the bullet is still accelerating in the moment before it exits the barrel, so yes, when ALL ELSE IS EQUAL, a longer barrel will produce more velocity.  The problem is that all else is almost never equal.  Powder drifts a little over time, lot to lot, up and down, so it's reasonable to expect a difference over time EVEN WITH THE SAME LOAD IN THE SAME PISTOL.  Different types of rifling and different twist rates in the same type of rifling will produce different velocities.  Then there's the barrel's inner diameter.  If one barrel is a hair narrower than another, that will decrease the rate of acceleration, but wait, if rate of acceleration is decreased, that causes the combustion chamber to expand at a slower rate, which increases pressure at a faster rate, which INCREASES the rate of acceleration, and MAY or may NOT result in a higher velocity by the time the bullet leaves the barrel.  There are ALL sort of things that play into this.  Pinning an anomaly down to just one thing is pretty difficult.

If I am at 1076 which is 39 fps above published max...I am okay because of the ability to run +P loads?

No.  You're okay because the fact that your incremental velocity increase is still increasing with each incremental powder increase suggests you aren't running into trouble with pressure.   +15, +17, +25 suggests that you're still in a good place. 

Also, would I be better served to switch to WSF and work up to minor from a slower powder

Not for 9mm minor action shooting.

[Wobbly]

Pinning an anomaly down to just one thing is pretty difficult.

Yeah, that was a favorite party game when I was young...
Pin the tail on the anomaly.

 

[1SOW]

I agree with ID about your load development.

Re the longer barrel vs reloading factors that can have an effect :   Yes a number of theoretical differences in the load can make a difference,  but 40 FPS is a BIG (avg. of 10) difference.  Two separate tests over several increasing loads comparing SD reloads with XTPs and Gold Dots,  showed very much the same gain when fired from the longer CZ barrels using the same powder.

Chronoing my minor PF loads out of different length barrels also show a very consistent gain in speed with the longer barrel pistols.

My "All else being the same"  referred to Bullet, Case, Powder and load.   Like all chrono results, there are some variations,  but nothing dramatic or out of the normal range of deviations found in most tests..

[nicky]

grains   10 drop avg    avg. vel.      ES   SD    +/-
-------   -------------    ---------       ---   ---     ---
4          39.7                 1019        44    17   
4.1        41.0                 1034       44    17    15
4.2        41.9                 1051       62    20    17
4.3        43.2                 1076       25      8    25

A couple of question using ptouchton's string as an example.

 Would it be safe to say that one could go higher with that ladder even though you may have past max velocity given in the data ?

 As long as there is a steady progression in velocity your good & to stop when the velocity drops?

[painter]

I'd go a tenth higher, and as long as I saw the same increase in velocity as the ladder shows, I might go another.

I'd stop when I got less than a 15-20 fps increase.

That said, the numbers for the 4.3 gr load look pretty good to me.