Unique Load with High velocity spread

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dbb1776

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Jan 19, 2010
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tx
Load:
38 special
158gr Swc, hard not swaged
4.7-5.0 Unique
Measured with scale calibrated with check weights
CCI Merc free primers
Case length within .003
Good crimp
Didn't check OAL
Worked up from 4.7 to 5.0. 150 FPS velocity from high to low with all charge weights.
What could cause this?
I have CCI 500 primers I will try next.
 
However, here is a simple answer, so long as you don't ask any follow-ups:

A) Load at least 10 rounds, using bullets and primers from the same box, powder from the same can, and brass with at least the same headstamp.

B) Collect instrument velocities and compute mean and SD

C) Ignore ES.

D) Divide an SD derived from at least 10 samples by the mean derived from the same samples and express as a percentage. Less than 1% is good; between 1% and 2% is not uncommon and not bad; over 3% implies a fair probabilty that something is wrong that requires further investigation.
RKG is offline .

having said that: IS your powdering metering even for sure?

Did you get a slight variation in in COL due to seating depth?

Did you shoot over the Chrono from a rest getting the bullets right into same area?

Was is getting to sunny on the Chrono?

If your groups are tight, do you care really?

You did not list the mean?
 
Not enough data. We must have data:)

How many rounds did you test,? what was the average, ES, SD etc.

Just saying 150 FPS difference between high and low does not mean much if it was only 2 rounds for example.

The larger the test (10 is minimum) the better the data.

Was it real hot? Cold? Distance from chrony?, lots of variables to consider.
 
Biggest thing I've found causing large velocity variations in .38 Special has been case neck tension. My 38/357 sizing die didn't size the thin .38 Special cases enough for good tight bullet grip. Don't know if this is your problem but different or loose bullet tension will cause the bullets to jump before good consistent ignition of powder. One solution is to run thin cases into a 9MM sizing die down just past where the bullet would stop. The extra couple thousandths more sizing then expanding with the .38 expander gives good tension. Check your bullet diameter and inside case neck diameter for a good tight fit.
 
Not to blaspheme here, but you can get better consistency by -- gasp! -- sorting your .38SPL cases by headstamp.

Case wall thickness varies a lot by manufacturer, and it is the culprit re: inconsistent neck tension. If you sort you can keep things more uniform.
 
Unique can give wide results based on where the powder is in the case when firing. Either against the bullet or against the primer.

This may be more promenent with larger cases such as 44 Special or 45 Colt than 38 Special.

Try tipping the barrel up or down before each shot and do it the same for the string.
 
Unless you are locking the gun in a ransom rest, there are so many variables as to accuracy that different headstamps are not going to make much difference, They certainly are not going to make a difference in 150 fps velocity. Not saying headstamp constancy is a bad thing.

If out of a large sample test the OP still gets such a wide variance I would try HP38 or Bullseye. I am just not a fan of Unique. But again there are still a lot of maybe's that are unknown.
 
I don't fully agree Rule 3; if one is chasing accuracy, one controls every variable one can control.

Headstamp wouldn't matter if all brass walls were uniform. But they're not. For example, R-P .38spl brass is thin-walled and unsuitable for .357" jacketed bullets, or at least less so than most other headstamps, because it does not provide good neck tension except with .358" slugs. I set it aside for lead loads only.

I do agree re: Bullseye. It's my go-to .38spl powder.
 
LUCK! I stumbled into a DEWC load that I shoot out of a 6" Rhino, 2" Rhino, and S&W 642. I use assorted 38SPC cases a 148 gr Berry's DEWC with 3.7 grains of Unique. They print wonderfully out of all 3 of those guns, plus an old timer's model 10 liked the load as well.

Per the above, need a lot more data. Why sweat it if you are consistent on the targets!
 
Honestly the main reason I'm sweatin this particular load is I was going to use it for a woods load and defense if needed. If something needs smacking I want to smack it at 900 fps, not 750.
I will double check data and make adjustments.
On a side note the 44 mag I loaded with several bullets and differen charge weights were all consistent and predictable. That's why this velocity difference surprised me.
Thanks for your input guys.
 
All I was trying to say about headstamps in revolvers, was in accuracy it may help a little, but impossible to measure with all the other variables involved.

As to a 150 fps velocity no way. I chronograph a lot of different loads in many calibers and have never seen that much variance in velocity unless a case split. The exact same load and bullet in a Rem case VS a Win case the velocity difference in a 38 spl is negligible.

But this is off the original post. The OP is talking velocity and we do not have enough info.
 
dbb1776,

Some more information, I got a S&W 642 a number of years ago and i had a heck of a time finding a load that shot relatively consistent velocities. I went through a number of powders and bullets and found a suitable combination. It drove me nuts.

While I understand that small groups do not translate to small velocity variances, but what I was experiencing was more than i felt was acceptable.

Good luck with your research.
 
"Unique can give wide results based on where the powder is in the case when firing. Either against the bullet or against the primer.

This may be more promenent with larger cases such as 44 Special or 45 Colt than 38 Special.

Try tipping the barrel up or down before each shot and do it the same for the string. "


I'm with Cfullgraf. Try his advise and post the results .
 
I just checked my 38 Special data, the only Unique load had an extreme spread of 167 fps. All of these loads, except for the Zero factory load, are thrown.

I consider any worries you have about extreme spreads to be much ado about nothing.


Code: 
[SIZE="3"]Colt Police Positive  Special 4" Barrel  	
					
125gr JHP 6.0 grs Unique  lot UN331 Fed 100? Primers		
1990					 
					
Ave Vel =	898	fps			
Std Dev =	60				
ES =	167	 			
High  =	983				
Low  =	816				
N =	6				
					
Zero 148gr LWC Factory				 
	4 Sept 2005 T = 72 °F				
					
Ave Vel =	810				
Std Dev =	72				 
ES =	213				
High  =	943				
Low  =	730				 
N =	6				 
					
					
158gr LSWC 5.4 grs AA#5  Mixed Cases Fed 100 Primers	
					 
					 
Ave Vel =	724	fps			
Std Dev =	40				
ES =	102	 			
High  =	763				
Low  =	661				
N =	6				
				 	
158 LRN  3.5grs Bullseye Mixed cases Fed 100 		
4-Sep-05	T = 72 °F				
Ave Vel =	759.2				
Std Dev =	36				
ES =	104.8				
High  =	813				
Low  =	709				
N =	32				
					
				 	 
					
	
					
158 JHP 3.4grs Green Dot Mixed cases Fed 100 		
4-Sep-05	T = 72 °F				 
Ave Vel =	548				 
Std Dev =	34				
ES =	138.1				 
High  =	631.9				 
Low  =	493.8				 
N =	24				 
					 
					
					
158 LRN  3.5grs Bullseye Mixed cases WSP 		 
29-Jan-06	T = 68 °F				 
Ave Vel =	760.3				
Std Dev =	27.53				 
ES =	111.4				 
High  =	814.1				 
Low  =	702.6				 
N =	29	[/SIZE]
 
I consider any worries you have about extreme spreads to be much ado about nothing.
Click to expand...

+1. I put it in the same category as "clean burning". If a handgun load is accurate, I don't concern myself with it's ES and SD numbers or any lack of clean burning characteristics.

Don
 
Yes, but the OP is looking for velocity as well (small spread).
So therefore "clean burning" is a necessary concern.
(at least in my experience)

YMMV
 
Yes, but the OP is looking for velocity as well (small spread).
So therefore "clean burning" is a necessary concern.
(at least in my experience)
Click to expand...

Well, if he is looking for more velocity, then he should use more powder. 4.7 to 5.0gr of Unique is not a Max load with a 158gr SWC in .38 Special. But, my point is, note that nothing was said about whether the load was accurate or not. With handgun loads, an accurate load trumps low ES and SD numbers as well as clean burning characteristics. Just MHO.

Don
 
I recently began doing lots more handgun loading, specifically in 38 Special and 44 Special and ran into this very thing. There were two problems:

First, I just thought I was crimping my bullets appropriately. After applying a more firm crimp, my crazy velocity variations ceased immediately. I thought a firm crimp was only necessary with slower burning powders until I ran into this.

Second, and far less often a problem, my chronograph gives questionable readings when the sun is directly overhead. I found much, much more predictable readings in early morning, late evenings and especially on overcast days.

Just to give you an idea of what to expect:
I did some extensive load development for my 3" Rossi 68 a few years ago. I loaded 5.0 grs. of Unique and a commercial 158 gr. SWC and out of that short-ish barrel velocities typically ran a little over 800 fps. Out of my wife's 2" Charter Arms Pink Lady, the same load averaged 775 fps.

35W
 
Funny this subject came up. I am investigating the exact same thing with my .357 Herco loads as I found a 150 FPS(!) extreme spread and the SD was around 42 FPS. Too much for me.

I'm changing exactly one element at a time. First thing is weighing the charges versus throwing, weighed a bunch last night and plan to test them through my 35P this morning.

I must admit that having a chronograph can be very useful as my favorite load with Herco doesn't seem to shoot as well as it used to... hmmm...
 
One lesson I learned after I got a chrono (35P) was that just because the ES and SD were low it does not require that the load is accurate for some reason. I have some high ES/SD loads that are quite accurate. Unique is one of prime examples of this issue.

Test on paper to be sure!

Also, I learned that it takes a good 20 shot + string to get good stats. I now normally only shoot 20 shot strings for stats.
 
Powder position in .38 Spl cases makes a big difference in velocity with some powders. Some powders are pretty good, some are awful, but most are going to lose in the 100 to 150 FPS range when the powder is forward against the bullet like when you have the barrel hanging down and raise it up to shoot. Some powders that do poorly powder forward do very well powder level. If you like to shoot long distance, or if your shots may be uphill or downhill depending on where you end up needing to shoot, it can make enough difference in drop to matter.

Other than that, if it is accurate at the range you are shooting, it's no big deal. I still wouldn't be happy with 100 plus extreme spreads. 50 or less is much better, and 25 or less makes me happy, while the occasional 15 or less ES is superb.
 
[SNIP] One lesson I learned after I got a chrono (35P) was that just because the ES and SD were low it does not require that the load is accurate for some reason. I have some high ES/SD loads that are quite accurate. Unique is one of prime examples of this issue.

Test on paper to be sure! [/SNIP]
Click to expand...

Sorry for the threadjack, but I'm beginning to think that something else has changed WRT my Herco loads as they used to shoot quite well IMO. Since Herco is Unique's slower brother they are likely to share at least some traits.

It is probably worth it for me to load up some Unique rounds with other components being equal and test them as well on paper and through the 35P. Could be interesting.
 
Considering you are shooting under 1000 fps loads, it is imperative to position yourself far enough away from the chronograph to prevent it from reading muzzle blast, rather than projectiles as intended. I position myself about 15' from the chrony, just don't shoot your chrony.

And OAL consistency will create some pretty good spreads in velocity, and some powders will only add to that problem.

And there are better powders available for 38 spcl. that will deliver more consistent pressures because they fill up the case more, reducing powder position issues. HS6 and Longshot are the one's I load with and have produced extremely consistent velocities, and upper end velocities too. And you did mention you would like to get at least 900 fps or so.

GS
 
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