Lies, Damn Lies, and Chrono results!

I recently realised that when my local range is quiet (most afternoons I'm all alone) I can set up my Chrono at about 15 feet in front of my favourite bay and, if I set my targets just right, I can shoot a lot of my Slow Fire practise over the Chrono and record almost every shot. It looks like this from the firing line:-

Unfortunately the range is only 15 yards maximum, but it is less than 10 minutes away and perfect for practise with standard 50' targets. I normally put a set of "900" targets up, but am currently focused on SF practise each day with my 22 and then my SARO wad gun - on the advice of my mentor Roddy. So I put up 6 SF targets at a time and can easily Chrono the lower 3 targets.

Since I'm trying to work up a reliable "soft" short line 45 load, this is a very time efficient setup. The only disadvantage is that I have not been able to get the Chrono to "talk" to my phone and so I'm having to release my grip after each shot and write down the result.

However, I have very little experience with the basic Caldwell Chrono and I don't know whether my results are representative of actuality.
Yesterday I used the Chrono on two SF targets with 4.1 N310 loads, but they did not reliably eject. Then I repeated one target with factory Federal GMM ammo as a kind of benchmark. 
Today I tried upping the powder to 4.2 N310 and it was more reliable, I used the Chrono for three SF targets.

It is very noticeable that the Standard Deviation for the Factory Ammo is much less than my reloads (I've been very careful to repeatedly check the powder drops for these small batches of ammo - I'm not seeing any significant variation - using an XL650 with Dillon measure and small bar - Brazos Hi-Tec 160 LSWC bullets).
The first shot today felt quite normal, but the Chrono reported a much higher velocity (in yellow). I think that is a Chrono error and I have excluded it from the table.
All of yesterday's strings and the first four strings of six today were fired almost perfectly over the body of the Chrono, but I was lazy to go and make a very small adjustment to the Chrono position for the last two strings, so the bullet path would have been slightly higher and to the right of the Chrono body. It is noticeable that the velocity results are quite a bit lower.

So, my questions to the Chrono experts out there. Are these SD results typical, or is there a problem with my setup or my Chrono?

Did your chrono come with a pair of diffusers that attached to the rods?
That may be part of the issue.....maybe not.

Yes - it comes with sun shades that clip onto the top of the rods, but other guys I know have found that they are not necessary in normal outdoor light. I have tried them previously with/without - did not seem to make any difference to readings.

I checked my N310 data with 185 JHP bullets. Your SDs are not much different, maybe a little larger than mine, but you're shooting a lighter bullet so the pressure might not be as high and that might make the speeds more variable.

S148. Very good info, thank you.

I intend to load another couple of batches with 4.2 & 4.3, then clean the gun and test those this week. I will run a string of Federal GMM each time to continue to establish a baseline.

Thanks.

Powder location in the cartridge can affect shot to shot velocity quite significantly. You can see this by firing 5 or 10 shots tipping the muzzle down before the shot and then 5 or 10 shots tipping the muzzle up before each shot. FWIW, accuracy on target is much more important than velocity. Do you have a 50 yard range you can test on?

A heavier crimp will hold the bullet a little longer and allow pressure to rise which can help consistency.

I found 4.4gr N310 with a medium crimp (~.465) was the best accuracy for SNS 160gr LSWC in my guns.

Shot location above the chrono sensor should not affect the velocity measurement. It will affect the detectability of the shot, but if it detects the shot, the timing should not be affected.

Finally, and most important, if you have to set the gun down between shots to write down the velocity, use that to train. Totally break your position, step back, then follow your entire process assuming your stance, aligning to the target, getting a grip on the pistol, breath, run your mental program, raise, settle, fire, call the shot and put the down and repeat.

I use N310 but I use Zero 185 JHP’s
For the long line I use 4.5 grains because the Zeros like to go a little faster and they hold inside the 10 ring but not quite the X. 
Speed is 10 shot Avg of 782

The sun is out, sometimes the chrono can see a reflection of the bullet instead of it passing over the sensor or a shadow.  This could change your readings, like the High one for first shot.  Sky screens will help avoid this.  My chrono works best on an overcast day.
David

To be frank, you are wasting time working up an accurate load using a chronograph. Your time would be better spent testing for accuracy with a machine rest or sandbags and scope if you are good at it. Otherwise, spend the time working on fundamentals.

BE Mike wrote:To be frank, you are wasting time working up an accurate load using a chronograph. Your time would be better spent testing for accuracy with a machine rest or sandbags and scope if you are good at it. Otherwise, spend the time working on fundamentals.

I disagree. You can gain a lot of useful information from chrono data. It all goes into the mixer and helps you with consistency.

Joel

SteveT wrote:Powder location in the cartridge can affect shot to shot velocity quite significantly. You can see this by firing 5 or 10 shots tipping the muzzle down before the shot and then 5 or 10 shots tipping the muzzle up before each shot. FWIW, accuracy on target is much more important than velocity. Do you have a 50 yard range you can test on?

A heavier crimp will hold the bullet a little longer and allow pressure to rise which can help consistency.

I found 4.4gr N310 with a medium crimp (~.465) was the best accuracy for SNS 160gr LSWC in my guns.

Shot location above the chrono sensor should not affect the velocity measurement. It will affect the detectability of the shot, but if it detects the shot, the timing should not be affected.

Finally, and most important, if you have to set the gun down between shots to write down the velocity, use that to train. Totally break your position, step back, then follow your entire process assuming your stance, aligning to the target, getting a grip on the pistol, breath, run your mental program, raise, settle, fire, call the shot and put the down and repeat.

+1.

Roy,
I suggest crimping down to 0.463" - 0.465" range with Brazos 160gr CSWC.

Also, my testing proves that SD is not that important for accuracy, especially at 25Y.
Lastly, chrono: I have two Oehlers 35P somewhere in the house collecting dust. Using such type of chronographs calls for the most favorable weather conditions (although Oehler is very good), and proper shots placement. Since I shoot a lot at indoor ranges, I switched to LabRadar, and never looked back. It works quite well at both indoor and outdoor settings.

AP

I called Labradar a few weeks ago and described my local range - they told me that their unit was not suitable - I bought one anyway, did not work at my range, took it to another full size, wide-open, outdoor range. Followed all of the instructions carefully, tried it in several different positions, could not make it work consistently. Either it or me was defective! Returned it. Ho hmmm.

I will try a tighter crimp on my next batches. Good suggestion.

I will also try to rig up a notepad and pencil to record numbers with my left hand - to avoid having to release grip between shots.

I take the point that Chrono data does not necessarily translate into improved scores, but my primary objective right now is to improve my reloading and produce reliable, consistent and, hopefully, accurate ammo for the short line.

I will do some more testing and report back.

Thanks for all of the very useful comments.

1joel1 wrote:

BE Mike wrote:To be frank, you are wasting time working up an accurate load using a chronograph. Your time would be better spent testing for accuracy with a machine rest or sandbags and scope if you are good at it. Otherwise, spend the time working on fundamentals.

I disagree. You can gain a lot of useful information from chrono data. It all goes into the mixer and helps you with consistency.

Joel

Yes, it is amazing that I made outdoor master and distinguished pistol shot without ever using a chronograph! I did use a Ransom Rest and even had my own set of portable turning targets. I worked on the fundamentals and at a certain point, I also studied the psychology of the game. There are so many good tried and true recipes for good bullseye pistol loads that there is little need for experimentation. Shooting as many matches as practicable also was in my plan.

The High Masers in our group have never used a chrono or a ransom rest.  Just learned how to shoot.

Bet their gun builders did.
Random rest anyway.

Well. Those are all valid comments. But, as my mentor keeps reminding me, I'm cramming what most folks take years to learn into one season. Made good progress on technique, but gun reliability has been an issue and I've not yet mastered reloading to the point where I'm confident to use it in competition.

Even though there are a lot of proven recipes on this forum, I still struggle to find the sweet spot for a short line 45 load (not to mention 32Acp!). So I will try all of the technology available in an effort to fast track my progress.

Onward and upward!

I’m curious, why did Labradar say their unit wouldn’t work? Ive only used mine indoors, not sure why outdoor should matter, but.....?

IMO, a chronograph is one of the best tools with which to get lost in the weeds. It tells you pretty much nothing about how to be a better shooter.

Greg,

Labradar were of the opinion that their unit is not reliable at short ranges (15yds in my case) and also any obstructions within the range are a problem.

I tried the Labradar once at my local range - got one reading and then no more. Gave up.

Took it with me on the next visit to the 25/50/100 yard "pistol" range at EEGC. Wide open, no obstructions, no other shooters that day. I got a few readings, but could not get it to follow the menus. Maybe I just didn't get the instructions. Don't know. Gave up. Returned it for a full refund.

I was shooting with Greg one time and he brought his lab radar. It works really well for me just barely in front of the shooting bench. I was testing 38 Special loads with WST & BE. Was able to get a reading every time in the SD was very small. Leads me to believe that it was functioning correctly because I was getting velocities in the range that I should have been. I really liked it and thought that it was great to know somebody that has one LOL
Jon

This thread has, like so many threads on this forum, kind of drifted quite a bit off topic. Never mind, I guess that is what makes threads interesting.

But, to get back to my original question - are the SD results of my Chrono testing OK? 

Today I loaded two batches of ammo, using a tighter crimp as recommended. Cleaned the gun thoroughly. Got set up as before, but, annoyingly, quite a few other shooters showed up today. Grrr...... So I had to "dodge & weave" a bit. It was a clear blue sky day, but the Chrono was in the shade of the main baffle structure, so I did not use the sun shades. I had quite a few "Error" readings - hence the blanks on the tables.


Seems like an SD of 20 to 30fps is typical. I think that the 2 strings of factory Federal GMM yesterday were somehow erroneous - can't explain why. The recoil of the gun today "felt" exactly similar to the averaged results. A couple of the "weak" shots gave low velocity reading - similarly a couple of the "snappy" shots gave high reading. The 4.2 reloads were not 100% reliable, neither were the 4.3's, but felt better and only one FTE I think. All of the groups were roughly consistent, ignoring a couple of flyers down to me.

I will load more of the 4.3 recipe and use that for further practise. If I get any FTE/FTF's in sustained fire then I'll go up to 4.4 and try again. As far as I am concerned the Chrono has helped me to home in on the "sweet" load that I'm looking for and I've also learned something along the way. I don't intend to use it often, but it is a useful tool to have in the armoury and it is important to learn how to use it correctly.

Yes, your 2nd string of GMM is way off. 
Use your opaque covers to give a consistent background.
Your first set of gmm is consistent with packaging velocity
So continue to use that setup, but with your covers.

I have chrono’d various ammo factory and reloads.  It was a while back and I did not save strings, just final avg velocities, but if I recall an SD of around 20 was what I saw mostly.

Except for Aguila round nose 200gr, which was a true standout at around 9.

My purpose was to test and emulate ASYM ammo speeds and SD with my own reloads.  The chrono helped me get it figured out quickly.

Then I followed up with RR testing to verify accuracy compared to ASYM and was pleased.

I did purchase a Labradar and it worked great inside and outside at 25/50yard, but after a few days use verifying what I already knew, it has been collecting dust.

I just wanted to know that I could reload consistently and was in “target” velocities.  The chrono and RR helped me gain confidence in my gear.  But after seeing that my own ammo would outshoot most champions, even if I couldn’t, I quit worrying about chronos and crimp size and got back to focusing on my part in the shooting process.

I agree with BE Mike in a way, that chronos are somewhat useless in larger picture, but sometimes you gotta see for yourself, just so you can stop thinking about it.  I stopped looking at my reloads for mistakes my head was making, so the chrono was a benefit in that dept.

As a note I reload one bullet, target .45 and I buy factory ammo for other calibers, vs. some friends that shoot and reload 20 calibers for rifle and pistol and seem incapable of firing a shot downrange without a chrono in front of them.  To each his own.  

willnewton wrote:I agree with BE Mike in a way, that chronos are somewhat useless in larger picture, but sometimes you gotta see for yourself, just so you can stop thinking about it.  I stopped looking at my reloads for mistakes my head was making, so the chrono was a benefit in that dept.

+1

You are calculating the standard deviation of 4 or 5 shoot sub-groups and then calculating an average standard deviation for the overall sample.  Mathematically, that's not really a valid method for determining the standard deviation of a sample.  To determine the standard deviation for a particular load, you should simply calculate the standard deviation based on all the shots together (the whole sample set) you have for that particular load.

I put your latest set of data in a spreadsheet and this is what I get:

4.2 B LSWC (29 data points) - Std Dev = 28.99
4.3 B LSWC (17 data points) - Std Dev = 33.54
Factory New (10 data points) - Std Dev = 24.84

You can see this does change the results.