38 Special chronograph issue

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SpangledHatch

SpangledHatch

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I went out to the range yesterday to test some attempts to replicate the Speer 135gr short barrel 38 +p round.

This is my first time chronographing, and I'm a little confused about some aspects of the results, specifically high standard deviation and extreme spread observed across all my testing, including the control groups with factory cartridges.

In short, I'm seeing SD's greater than 30, and ES's of 90 and above with all tests. Velocities are a little lower than I expected as well.

I loaded these cartridges very carefully - all brass is of the same headstamp (once fired), each charge was hand weighed, and overall length was tightly controlled.

I was about 6 feet from the front of the chrono. The only thing I can think of is maybe getting a little more distance.

Any input appreciated.

Load data used from https://www.speer-ammo.com/download...iber_357-358_dia/38_Special_P_135_GDHP_SB.pdf

My chronograph data is as follows:

Code: 
135gr Speer GDHP SB .38 S&W Special

2/3/2020 - 70F - 30% Humidity - S&W 442 1 7/8" bbl

CCI 500 Primer
Remington-Peters Nickle Brass
1.450" COL

4.8gr Unique - MV 700 fps, SD 49, ES 136

622 fps
718 fps
692 fps
758 fps
711 fps

5.0gr Unique - MV 741 fps, SD 32, ES 90

NR
752 fps
NR
784 fps
769 fps

694 fps
776 fps
722 fps
719 fps
717 fps

5.2gr Unique - MV 776 fps, SD 41, ES 142

752 fps
814 fps
759 fps
789 fps
739 fps

697 fps
765 fps
839 fps
808 fps
795 fps

Factory - MV 781 fps, SD 36, ES 118

698 fps
785 fps
NR
NR
816 fps

779 fps
785 fps
782 fps
808 fps
800 fps
 
wide extreme spreads are not unusual with the 38 special. It is a long case with a large volume and there is often a lot of empty space when loaded. This leads to inconsistent ignition from one shot to another. So, this is 'normal'.

You can try moving the chronograph a little farther away, but don't be surprised if you get the same results.
 
Welcome to reality. It’s a bit disconcerting anticipating single digit SDs and ESs. Your results are similar to what I see for .38 and certain powders.
A couple of other points:
You may want to obtain enough factory ammo to use as a calibration load for your chronograph to see if it’s performing as you’d expect, before sending your test loads through.
You’ll need a bigger sample to really judge SD numbers. But don’t be surprised if you still have SDs in the 30-50 range.
If you’re using a shoot through chrono, try to make sure all bullet trajectories are the same, perpendicular to the plane of the sensors, and level through them as well. It’s measuring delta T across a known distance and angular variation can cause V differences.
Use a sharpie to blacken the bullets, the sensors may detect the darker color better. Use your sky screens and try to ensure the the sensors are evenly illuminated (no shadows on just one).
You can try elevating the muzzle before each shot, that is if your range SOP allows it, that way the powder is in the same position each time. It may lower your ESs. That’s not typically how any of us shoot, but, you can at least see if that’s getting your closer to whatever expectation you have. Good luck!
 
fxvr5 said:
wide extreme spreads are not unusual with the 38 special. It is a long case with a large volume and there is often a lot of empty space when loaded. This leads to inconsistent ignition from one shot to another. So, this is 'normal'.

You can try moving the chronograph a little farther away, but don't be surprised if you get the same results.
Click to expand...
Agreed, one thing you can do is point the revolver up and bring the barrel down level slowly to keep the powder rearward against the primer, that will give better ES/SD numbers. of course you'll have to do it in the field as well to match.

If you had one shot where the barrel was up first, then another where it was down first, you'll get big ES/SD numbers.

I test powder back vs powder forward myself. BE-86 is one of the more forgiving powders as far as powder position in .38 Spl at top .38 Spl pressure levels.

WST and Clays are two good ones for plinker level pressures.
 
SpangledHatch said:
Which would be fine advice if I weren't shooting SD loads out of a snubby...
Click to expand...
Sorry, obviously I wasn't paying attention to the figures. Not bad at all velocity wise from a snubby. Bullseye or W231 probably would reduce the ES but you'd probably loose a tad off the top end. Walkalong's usual good advise to try BE86 is probably an excellent idea, I've never tried it because I can't find it.
 
Mag primer. Find a powder that fills the case more. Tighter crimp. I run a 158gr. +p at 1004 fps out of a 2.5" revolver. And 946 fps out of a 2".

The only way to get single digit sd #'s it to up the pressure or go with 3f black powder.

You would be surprised at the black powder consistency and velocity!
 
Chronograph's are a rather finicky instrument. Their readings can be affected by environment and other inputs that get picked up. I agree with drband that a greater distance between muzzle and chrono should be used to avoid miscellaneous input that can produce greater variation in data. When I was learning how to get good readings from my chrono I found that firing too close to the chrono produced errant reading that most likely came from smoke passing across the pickups. Usually i set my chrono at 5 to 7 yds away. I have experienced errant readings from sunlight reflecting from vehicles pulling into the parking behind the range and one time from lightning from far away storm clouds.

I am generally happy with SD's around 20 fps but you just need to accept the numbers you get and figure out how important they are. Have loaded a lot of ammo that didn't show great consistent numbers over the chrono but produced good groups on paper.
 
► Quality of the light is another big point of error. I prefer to chrono on overcast days, when the light is bright, but highly diffused by cloud cover.

In mid-summer when I can't find a cloudy day, I have been known to take one of the white covers off one of my wife's large plastic storage bins, and then balance that across the top of the 4 chrono V-wires.

► Case volume also has a big effect. Maybe not so much with 38Spcl, but it has a huge effect on auto pistol testing. Try using all cases with the same head stamp.
 
Last edited:
I stand by my recommendation of bullseye for your load. also, run some speer short barrel factory ammo over that chrono and compare to your reloads.

luck,

murf
 
murf said:
I stand by my recommendation of bullseye for your load. also, run some speer short barrel factory ammo over that chrono and compare to your reloads.

luck,

murf
Click to expand...

I did that (factory control groups) - it's in the data posted. The 5.2gr Unique load comes very close. Similar ES and SD numbers were seen with factory rounds.
 
SpangledHatch said:
I did that (factory control groups) - it's in the data posted. The 5.2gr Unique load comes very close. Similar ES and SD numbers were seen with factory rounds.
Click to expand...
I see that now. I would shoot the factory rounds through the chrono, again, this time at 12 to 15 feet away from it. compare with your first chrono data and see if the powder blast has an affect on the results.

I still recommend a faster powder for this load.

luck,

murf
 
Steve C said:
Chronograph's are a rather finicky instrument. Their readings can be affected by environment and other inputs that get picked up. I agree with drband that a greater distance between muzzle and chrono should be used to avoid miscellaneous input that can produce greater variation in data. When I was learning how to get good readings from my chrono I found that firing too close to the chrono produced errant reading that most likely came from smoke passing across the pickups. Usually i set my chrono at 5 to 7 yds away. I have experienced errant readings from sunlight reflecting from vehicles pulling into the parking behind the range and one time from lightning from far away storm clouds.

I am generally happy with SD's around 20 fps but you just need to accept the numbers you get and figure out how important they are. Have loaded a lot of ammo that didn't show great consistent numbers over the chrono but produced good groups on paper.
Click to expand...
 
One thing not yet mentioned. With a revolver, one typically uses all the chambers in the cylinder. So, one is going to have five or six (or twenty, whatever) different combinations of chamber diameter and alignment for a 'string' of shots. By using one chamber at a time, one will normally see which chamber is fastest, which is slowest, which is most consistent and so on. When I load self-defense ammunition for a revolver, I strive to get 'suitable' velocity out the slowest chamber and move on. I tend to use the heaviest and bluntest bullets I can find.
 
Walkalong said:
Agreed, one thing you can do is point the revolver up and bring the barrel down level slowly to keep the powder rearward against the primer, that will give better ES/SD numbers. of course you'll have to do it in the field as well to match.
Click to expand...

I've seen this variability in spades with 45 Colt. I have not tested the concept with other cartridges but I am sure the powder location in large volume, older cartridges will experience the difference.

Around the year 2000, I was working on consistent loads in my 38 Special S&W M642. I had huge velocity variabilities. I worked with several different powders and found one that gave fairly consistent results. At the time, I did not do the "powder against primer" or "powder against the bullet testing. I should do the testing again if I get inspired to do so.

In any case, you have to do lots of testing with different powders.

P.S. Winchester 231 provided better, consistent results in my gun with 158 grain SWC bullets. But, other powders that I did not work with may be better or equal performance.
 
Old Stumpy said:
Had a .45 Colt issue with my Chrony, leading to inaccuracy.

A bullet through the rear sensor will do that though.
Click to expand...
Ya, they ain’t bullet proof. Some guys do try and boiler plate them.
An early one I had was just 3x5 printed cards held in metal clips. At least That required some finess.
 
.38 Special with Unique powder tends to give me erratic velocities with 110-125 grain bullets. A switch to Accurate Arms #2 powder reduced extreme velocity spreads to small numbers. Also neck tension on the bullet can be responsible for big variations. If your expander die is doing nothing you may be having low neck tension. This can cause the bullet to start moving just from primer ignition which creates extra space for the powder to burn reducing pressure.
 
whughett said:
Ya, they ain’t bullet proof.
Click to expand...

Yes, you need to always set them up well so that you can fire from a rest every time. Otherwise one little slip and you are done. Funny thing was that I had replaced the steel rods with dowel rods in case I ever hit one. That and lightweight plastic sheet for the light shields. Chrony doesn't provide much in the way of replacement parts.
 
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