Chrono'd my 45 reloads for the first time. How'd I do?

[Rockrivr1]

So I finally was able to Chrono my 45 loads to see where I stand. This is the first and only rounds I reload right now and they have shot pretty good for me, but up until yesterday I had no idea of how they were performing. I ran 6 rounds through the Chrono and got the following readings

761
779
740
750
751
761

Average of 757
Power Factor = 174
13% Standard Deviation

Seeing this is my first time using a Chrono I'm thinking these results are pretty good. I was shooting for a load that would make Major in USPSA and shoot well for me. The accuracy is there and I'm above the 165 PF needed to make Major.

My question though is should I try to tweak this some more to get a little bit lower power factor and try to reduce the standard deviation or would it be more of a hassle then it's worth?

Tweak or leave be?

 

[Scalce]

It's a disease don't start.

It seems that you are using 230s right?

What bullet type, powder, charge, OAL, mixed brass, etc?

Lowering the charge to lower the velocities won't lower your SD.

Standard deviation is a calculation of the spread between all your shots.

Typically you want to shoot a minimum of 10 rounds to get good readings.

13% is pretty good if you are loading on a progressive with random cases.

I can get a SD of 6-8% on 9mm with random cases and using my Dillon 650 but 45 seems to be more case sensitive. I have gotten down to 13.1% but that could be a fluke.

Outside temperature and humidity can affect the velocity so don't try to get too close to the minimum pf.

I would say 50 fps above provides enough buffer so you may be good where you are.

Take some more reading with a larger number of rounds and post back.

I think this thread may belong in the reloading section.

 

[Adam_MA]

If this load is shooting well for you, is accurate, and you are able to manage the recoil sufficiently to meet your goals in competition, I would leave them right were they are.

PS. Moving to Reloading Forum.

 

[EddieCoyle]

Troy, 13% SD is damn good for .45 ACP. One way to tighten it up is to sort the cases - not just by headstamp but also by length and the number of times that they've been fired.

Don't expect too much of an improvement though - 13% is pretty good.

 

[TY43215]

The lowest power factor you got was 170. I would drop the load just a hair so no PF is below 167 and go from there. If you can get your average to be 170 you will probably be better off providing it is doing what you want it to do.

Remember, every chrono is different and at major matches they use 2 in tandem. Don't cut it too close or you will be shooting minor with near major loads.

Regards,

 

[Dick]

Some notes on standard deviation - the units are not %, but rather the same units as the original measurements, in this case feet per second. So, the 13 (actually, I calculated either 11.03 or 12.08, depending on whether the sd of interest is that of the 6-shot group or that of the statistical population of possible results that the 6-shot group is a "sample" of - - but that doesn't matter) represents an sd of 13 fps, not 13%.

The reason this should be of interest is that one would expect a group of larger numbers (say, rifle cartridge velocities of perhaps 3,000 fps) to have higher standard deviation than a group of smaller numbers such as pistol cartridge velocities. An sd of 13 fps for a group of numbers averaging 3,000 clearly represents less variation than the same sd for a group of numbers averaging 750. Similarly, and perhaps more relevant to the case at hand, one would expect a group of .45 ACP velocities to have a smaller sd than a group of .357 Mag velocities, even if both had the same inherent variability. So, simply comparing sd across different groups of results isn't necessarily informative. (As an aside, this phenomenon, i.e., the sd being positively correlated with the mean, is called heteroscedasticity and has major significance for using statistics in hypothesis testing.)

The way to compare apples and apples is to express the sd as a percentage of the mean (aka the arithmetic average), which yields a statistic called the coefficient of variation, abbreviated CV. Using the original data, the CV = (13/757)*100 = 1.7%. I've spent a lot of time shooting over chronographs and analyzing the results, and that's a very consistent set of velocity readings indeed.

 

[Scalce]

Your right Dick.

I had a brainfart because the original post had SD as a %.

I plugged his numbers into my CED M2 software and got this:

String 1
1) 761.0 4.0
2) 779.0 22.0
3) 740.0 -17.0
4) 750.0 -7.0
5) 751.0 -6.0
6) 761.0 4.0

High: 779.0
Low: 740.0
E.S.: 39.0
Ave.: 757.0
S.D.: 13.3
95%: ±15.3

He needs to chrono more rounds to get a more accurate reading.

 

[adweisbe]

When you are chronoing to meet power factor do they take the average of the whole string or does every single shot have to be major?

 

[Dick]

OK - yes, 13.3 is correct. I did the calculations in Excel and apparently made an error transcribing numbers.

FYI, the sd the CED M2 software is calculating is the population sd, i.e., it assumes the data are "sampled" from a larger statistical population of potential results. The corresponding sd if the 6 shots were considered the entire population would be 12.17. As you probably know, the difference between the two sd's becomes smaller as n becomes larger and approaches zero as n approaches infinity.

 

[Dick]

When you are chronoing to meet power factor do they take the average of the whole string or does every single shot have to be major?

Apparently (I don't shoot USPSA, so I did a quick search), it's the average velocity of a 3-round string, with a bit more complication if the average of the first string is too low. More details here: http://www.uspsa.org/rules/14th_Ed_US_html/14th_Ed_US_Rules.6.html

 

[GTOShootr]

When you are chronoing to meet power factor do they take the average of the whole string or does every single shot have to be major?

They take eight. They pull one for your weight and shoot three. If the three averaged don't make major (or minor), they shoot the remainder. If you still don't make major, you have a choice with the last one, weigh it or shoot it. I made 164.5 at my first Area 7. Make sure your bullets weigh what you think they weigh!

If you are shooting locally, where they don't chrono, don't be too worried about a buffer on top of 165pf. Make major but if you aren't travelling the buffer isn't all that significant. It is there for the odd temperature swing or crazy chrono that may cause lower readings than you expect.

After Sunday, I'm betting adweisbe's rounds are making major.

 

[Rockrivr1]

It's a disease don't start.

It seems that you are using 230s right?

What bullet type, powder, charge, OAL, mixed brass, etc?

Lowering the charge to lower the velocities won't lower your SD.

Standard deviation is a calculation of the spread between all your shots.

Typically you want to shoot a minimum of 10 rounds to get good readings.

13% is pretty good if you are loading on a progressive with random cases.

I can get a SD of 6-8% on 9mm with random cases and using my Dillon 650 but 45 seems to be more case sensitive. I have gotten down to 13.1% but that could be a fluke.

Outside temperature and humidity can affect the velocity so don't try to get too close to the minimum pf.

I would say 50 fps above provides enough buffer so you may be good where you are.

Take some more reading with a larger number of rounds and post back.

I think this thread may belong in the reloading section.

I was using mixed cases that were once fired. Powder was 5.2 grns of W231 on a Dillon 550 using Zero 230gr FMJ bullets.

At this point I may just leave this setting alone. I still new enough at this that I may go to far and unfortunately I don't have a Chrono myself. Hummm, that may have to be the next big purchase for me. I'll shoot more rounds the next time I can get my hands on one.

As to the SD, I used a percentage as I thought that was correct. Thanks for the clarification.

I appreciate the input.

 

[Lugnut]

I was using mixed cases that were once fired. Powder was 5.2 grns of W231 on a Dillon 550 using Zero 230gr FMJ bullets.

That is very interesting.... I chrono'd a bunch of my loads thru my 1911 last week. My readings all came in at an average of 710 ft/sec... with basically the same load- 5.2gr W231, Winchester primers, 230 FMJ (Speer) and COL 1.265". I'm surprised ours are so different!

 

[TY43215]

That is very interesting.... I chrono'd a bunch of my loads thru my 1911 last week. My readings all came in at an average of 710 ft/sec... with basically the same load- 5.2gr W231, Winchester primers, 230 FMJ (Speer) and COL 1.265". I'm surprised ours are so different!

Every barrel is different as is every bullet manufacturer. That is the reason I reload. I don't figure to save money, I figure to get a better finished product.

 

[Gammon]

I don't pay any attention to SD. The only thing that counts is the extreme spread. If you have an extreme spread of 30 fps, load your ammo so that the slowest round just makes major; this has worked for me without fail for many years.

 

[Scalce]

Every barrel is different as is every bullet manufacturer. That is the reason I reload. I don't figure to save money, I figure to get a better finished product.

That is true for accuracy but if the barrel length and twist rates are identical the fps should be relativley close if the same type and weight bullet is used.

Environmental variables, distance from chrono, muzzle blast gas, etc, can affect the readings.

My buddy who is a member at MRA just got the same chrono I have and he also has a 5" 1911 but totally different manufacturer and we are almost dead on with velocities.

We are both using the same type of bullet but from different companys.

 

[Rockrivr1]

That is very interesting.... I chrono'd a bunch of my loads thru my 1911 last week. My readings all came in at an average of 710 ft/sec... with basically the same load- 5.2gr W231, Winchester primers, 230 FMJ (Speer) and COL 1.265". I'm surprised ours are so different!

Interesting. You know the one variable that may be the deciding factor is the actual accuracy, or varience, of the different scales being used. Granted, for that much of a difference the scales would need to be off by a big margin. I gave up on using electronic scales and just use a RCBS balance beem scale. It says 5.2 grains when I measure, but as with anything, it's a piece of equipment.

 

[TonyD]

I just returned from the range. My .45's through a 5" 1911, mixed brass, CCI LP primers, 230 RN moly coated Lead, 5.0 grs. W231:

Mean velocity = 802.4 fps
Extreme Spread = 14.4

Sunny @ 92f

Loaded on RCBS 4X4, RCBS dies with roll crimp/seater die.

 

[adweisbe]

Roll crimp in .45ACP? I find that moly bullets move fast compared to the book.

 

[Lugnut]

Interesting. You know the one variable that may be the deciding factor is the actual accuracy, or varience, of the different scales being used. Granted, for that much of a difference the scales would need to be off by a big margin. I gave up on using electronic scales and just use a RCBS balance beem scale. It says 5.2 grains when I measure, but as with anything, it's a piece of equipment.

I use the RSBS balance beam scale as well.... I think it's a fairly inexpensive one- can't remember the model name offhand. It came with my Rock Chucker kit.

 

[TonyD]

Roll crimp in .45ACP? I find that moly bullets move fast compared to the book.

That what the die is and it works fine.

 

[vellnueve]

I don't chrono any of my loads. I use the starting loads suggested and never deviate. As long as they shoot straight and group nicely, I'm happy.

 

[TonyD]

I don't chrono any of my loads. I use the starting loads suggested and never deviate. As long as they shoot straight and group nicely, I'm happy.

Then you're probably not getting the most out of your reloads (by sticking to the starting data). I didn't have a chrony the first two years I loaded. I simply worked up the load to find the best accuracy - the most important part. I picked up the cheapest chrony I could find to check my reloading procedures for consistency. Also, I needed to work up a .308 load that would still be supersonic at 1k and a chrony is the only way. I don't think they are necessary for general purpose applications.

 

[vellnueve]

Probably correct. All my reloading is for just casual target shooting practice except for my 7.5 Swiss which is for everything.

These loads are still more accurate than I am at this point.

 

[Lugnut]

Every barrel is different as is every bullet manufacturer. That is the reason I reload. I don't figure to save money, I figure to get a better finished product.

Well now this is strange... but Troy here's some datapoints for you.

I just got a new CED Pro Chrono and tested another batch of my .45ACPs. 5.2gr W231, CCI Primers, 230FMJ (Berrys), 1911. These measure much faster on average than the other time using someone else's chrono.

My loads sucked... I was relaoding slow and didn't get into a rythm on this small batch so I suspect that is why the numbers look the way they did:

20 shot string:
Hi 795
Lo 684
Av 741
Es 111
SD 31

Another 30 shot string:
Hi 802
Lo 667
Av 737
Es 135
SD 30


The interesting this is the first round of each magazine was the slowest eveytime from what I recall. I know at least a few of the first shots in the mag were in the 600s.

Either way, I'd say you did very well with your batch!

 

[RKG]

So I finally was able to Chrono my 45 loads to see where I stand. This is the first and only rounds I reload right now and they have shot pretty good for me, but up until yesterday I had no idea of how they were performing. I ran 6 rounds through the Chrono and got the following readings

761
779
740
750
751
761

Average of 757
Power Factor = 174
13% Standard Deviation

Seeing this is my first time using a Chrono I'm thinking these results are pretty good. I was shooting for a load that would make Major in USPSA and shoot well for me. The accuracy is there and I'm above the 165 PF needed to make Major.

My question though is should I try to tweak this some more to get a little bit lower power factor and try to reduce the standard deviation or would it be more of a hassle then it's worth?

Tweak or leave be?

??? 13% of 757 fps would be 98 fps, and a sample standard deviation of 98 fps for a 750 fps round would be awful.

In fact, by my calculations, your sample standard deviation was 13.34 fps (not %), which is about 1.76% and quite respectable. Not only do I think that you would be hard pressed to reduce the SD(s) without a huge amount of effort, but I seriously doubt that any reduction would yield a noticeable enhancement of real world accuracy.

Edit: Apologies: As is often the case, I wrote the foregoing immediately after reading the original post, and without realizing that the point had already been covered by others.