Why can pistol loading data be so inaccurate?

[Old Scratch]

After loading rifle and pistol ammunition for more than thirty years, I must note the considerable discrepancies between manufacturers' claims and actual performance when it comes to pistol load data.

No, I don't think my chronograph is broken. I have found Sierra and Speer data to be quite reasonably consistent with what I can reproduce from my own bench (after all, reproducibility is the benchmark of good science). Add the caveat that some Speer pistol data seems a bit sanguine at times.

Then there is 7.62x25 when fired from a Tokarev pistol. This is where the "data" starts to get a bit absurd. Factory AA#9 data claims 1913 fps with an 85 grain bullet. Where is Allen Funt with his hidden camera?

I reproduced this load to get 1450 fps. Not at all bad, but certainly not the 690 foot pounds of energy that their claimed velocity would represent. Using AA#9 along with a bench rest rifle primer and S&B cases, I have managed to nudge 1700 fps, barely. I consider this an incredible load for a pocket pistol...but far short of what the factory would have had me believe.

Question: have others experienced such fictions?

 

[JTQ]

What barrel length are you shooting the round out of?

 

[Old Scratch]

Standard TT-33 Tokarev pistol. Unmodified.

 

[J2FLAN]

Well, there are so many different ways loads are tested, it would be had to pin down an answer. I am sure you have noticed, the difference in what the mfg. post and what manuals have listed. It leaves me with a pounding head, so I just work with a load until I get what I am after. I use the mfg. data as a guide. not the end all. Looks like you did a fine job with your 7.62x25

 

[Otto]

Factory AA#9 data claims 1913 fps with an 85 grain bullet.

Where are you getting this information? I don't see it in Accurate / Western online load manual. Are you using current manufacturers data?

For the most up-to-date loads, contact Western http://www.accuratepowder.com/contact-us/

 

[Old Scratch]

The most recent data published is not really the question. The data I quoted came in the printed pamphlet that accompanied my Lee dies. I bought the dies three years ago.

Fellow online correspendent Clark has quoted this same data claimed from the manufacturer in his posts.

This is Clark's quote:

"13.5 gr AA#9 is max AA book load, 86 gr FMJ, 1913 fps, 41.8k cup"

I'm not faulting Clark...he didn't invent this...he was just quoting the same preposterous data I read.

Has the manufacturer actually downgraded this load from a claimed 1913 fps to 1450 fps? That would be news unto itself. If so, please supply such website.

 

[kcofohio]

Maybe a misprint?

I found data listing a Hornady 86 gr. RN with 13.5 gr. of AA #9, 1683 fps, 41,800 CUP, barrel length 4.8", COAL 1.316".

The note on the data list this as +P and only recommends it shot out of a CZ-52, as it may be too hot for other guns.

Also list the start load @ 9.6 gr.



A better response would be received in the Handloader and Reloading section.

 

[Otto]

The most recent data published is not really the question. The data I quoted came in the printed pamphlet that accompanied my Lee dies. I bought the dies three years ago.

Great....then ask Lee.

 

[ny32182]

I learned long ago that all published load data is just a basic reference starting point, and your actual performance will vary considerably.

You are most likely using different brass, different barrel, different primer, different weather conditions, different chrono, different.....

Your mileage WILL vary.

 

[Sunray]

Actual loading data only applies to the firearm(if it is one), the components and conditions on the day of the test.
Like Otto says, there is no 7.62 x 25 data on Accurate's site. What factory?
85 grain data on Handloads.com(no AA #9 data or Accurate 7.62 x 25 data there either) indicates 1100ish to 1290ish with AA #5, Bullseye and Unique.

 

[jmr40]

The load data published is accurate in the guns or barrels used to test the data. In your guns the same load could be 100 fps faster or slower. In my guns the published data could be right on the money. Nothing new or unusual about this.

 

[RainDodger]

Alan Funt? Boy, are you dating yourself. I know exactly who he is - he's gotta be dead by now.

 

[Steve C]

Accurate used test barrels for some of their data in earlier load information. For example they use a 10" barrel for the .41 mag in 1999 data. This will add another 200 to 500 fps over data obtained from a 6" revolver.

My experience with Speer and Sierra manuals mirror your results with their velocity results being very close to actual chrono'd data with any small differences easily expected from using a different gun.

 

[horseman1]

Caution: I found this in an older manual and the data may have been superseded by newer data

I was digging around to see if I could find your load data. I found this in the 2003 version of their reloading manual. Be careful of the cut and paste formatting on this post, it came out kind of strange.....

7.62 x 25mm TOKAREV (CZ-52 only)
Gun DOUGLAS Barrel length 9"
Primer CCI 500 Case Starline
Powder Start Chg. Velocity Max. Chg. Velocity
SRA 85 RN OAL = 1.316"
No. 2 5.9 1509 6.5 1640
No. 5 7.7 1625 8.5 1766
No. 7 9.2 1631 10.2 1773
No. 9 11.8 1814 13.1 1972

Hope this helps in some way,

H1

 

[Mad Chemist]

I think the 9'' bbl explains most of the discrepancy.

 

[cfullgraf]

Just a reminder, any data provided by Lee was copied from some other source and is usually a cycle or two behind the current data from the manufacturer.

Here is a link to a blog from Western Powders that has updated 2015 data for the 7.62x25

http://blog.westernpowders.com/wp-content/uploads/2015/02/9X18Mak_7.62Tok.pdf

Western Powder's current data, Version 5, does not have the 7.62x25 listed.

http://www.accuratepowder.com/wp-content/uploads/2010/09/WP_LoadSpec_7-2-13.pdf

Contacting Western Powders and getting the poop direct from the horse's mouth might be prudent here.

 

[RPegram]

I don't know about powder manufacturers, but factory ammo makers use a single shot barrel in the length mentioned on box. I was watching a show the other day with a rep from Hornandy talking about how they get their data for their loads and why it is almost impossible to duplicate these results with a semiautomatic pistol or a revolver. Basically he said they load one round, close the chamber and fire it. It is not a gun, just a single shot solid barrel. The round they were specifically talking about was a 44 magnum, 240 grain XTP with a claim of over 1,600 feet per second. The only gun capable of achieving this, was a bolt action rifle, which actually went over due to a 16" barrel. All the hand guns were less with a snubby coming in with around 1,200 feet per second. My guess is that powder manufacturers do the same thing, which is why their published data is so difficult to achieve.

 

[someguy2800]

Thats why I like some of the older load data from Speer. Most of data in the old books was actually tested in real guns and they just used pressure signs just like a handloader would to recommend maxes and minimums. Lyman is also pretty good about using realistic barrel lengths for there load data. I just laugh whenever I see handgun velocity listed from 12 inch test barrels. Who does that help?

 

[Toprudder]

I have tried over 30 different pistol powders, all were chronographed, and rarely do I get the velocities published by the powder manufacturers.

I find that I get much closer correlation with the data in the Speer manual, especially when I am using plated bullets and I use the data for their TMJ bullets (heavy plated). I sometimes get good correlation with the data in the Hornady manual.

One time I tried PB powder in 9mm with 115gn bullets. The max load they had listed on the Hodgdon website would not even cycle my gun. That happened with one other powder also but I don't remember off the top of my head which it was now.

In 90% of the cases, the velocity I get is lower than published data. Sometimes that can be accounted for by the barrel length, but most of the time it is not.

Something to remember, for revolver rounds, is that the published load data is sometimes shot from a universal receiver, which has no cylinder/barrel gap. I also believe the length is measured from the breech and not from the front face of a cylinder, as the barrel length on a revolver is measured.

 

[Slamfire]

Accurate Arms manuals have been the least reliable in my experience. As an example, the AA Manual I had, for the 44 Special, it gave a maximum charge of 6.7 grains of AA#5 under a 240 lead bullet. The loads were developed in a Colt pistol, not a pressure barrel. I duly started off below that level and worked my way up. The velocity was pathetic. Next time out I bumped up the charge almost two grains above the Accurate Arms maximum. I decided that nine grains gave me all the velocity and accuracy I wanted. I have always been skeptical of Accurate Arms data and have no idea why their developed loads are so unreliable.

[SIZE="3"][B]4" M624[/B]
   			
240 LSWC   [B]6.1 grs AA#[/B]5  thrown,  Lot 35 590,  Mixed Brass WLP	
T = 62 °F	25-Feb-07				
		 			
Ave Vel =	523.1				
Std Dev =	31.1		 		
ES =	121.9		 		
Low = 	585.1				
High = 	463.1				
N =	28				
Accurate, light recoil, lots of unburnt powder	
					
240 LSWC   [B]6.7 grs AA#5[/B]  Lot 35 590 Mixed Brass WLP	
T = 62 °F	25-Feb-07				
					
Ave Vel =	571.1				
Std Dev =	34.46		 		
ES =	142.6		 		
Low = 	645.4				
High = 	503.4				
N =	32				
accurate, light recoil, lots of unburnt powder	
					
240 LSWC   [B]8.5 grs AA#5[/B] Lot 35 590  Mixed Brass WLP	
T = 64 °F	3-Mar-07	
			
Ave Vel =	790.4				
Std Dev =	30.69				
ES =	134				
High = 	845.7				
Low = 	711.6				
N =	32				
Accurate			
					
240 LSWC   [b]9.0 grs AA#5[/b] Lot 35 590  Mixed Brass WLP	
T = 64 °F	3-Mar-07	
		
Ave Vel =	845.5				
Std Dev =	17.43				
ES =	51.74				
High = 	869.9				
Low = 	818.1				
N =	10				
Very Accurate		
			
					
240 LSWC   [B]9.5 grs AA#5 [/B]Lot 35 590  Mixed Brass WLP	
T = 64 °F	3-Mar-07				
		 			
Ave Vel =	901.3				
Std Dev =	13.6				
ES =	41.57				
High = 	922.6				
Low = 	881				
N =	8				
Very Accurate, barrel leading	[/SIZE]

 

[ATLDave]

I really like my Lee press and Lee dies. I have zero use for Lee data.

 

[mdi]

Try this scenario;

You have 25 lab technicians in a room and instruct them to go back to their respective labs and develop loads for a specific caliber. Each lab tech uses his own lot of powder, primers and bullets, and mebbe different runs of cases. Each lab tech uses their own equipment and some use universal receivers (well worn or fairly new?) and some will use real guns (how much wear and tear on the gun?). Each will use the measuring equipment in their lab which may very well be different than other testing labs. Some of the techs may have decades of experience and some may have just a short time testing. So with all these variables they each come up with their own specific results and publish them. What are the chances they will all be exactly the same or the same as what your chrony says?

 

[Hondo 60]

Just looked it up, Allen Funt died Sept 5, 1999.

Revolver rounds seem to be the worst when it comes to factory ammo discrepancies.
Some mfgs use a pressure barrel that has no barrel/cylinder gap.
Some of which are 10" or longer.

Now if they use a 10" pressure barrel just how much is it going to be dfferent if I have a 4" revolver?

I think it's false advertising, but they never asked my opinion.

 

[horseman1]

I envision someone in marketing is overseeing the testing .

"Ok everybody, run that same test again until you get way2many feet/sec. Jim, your Crony always reads high, give it to Julie since her powder scale hasnt been calibrated since the 80's and lets see what we get! Oh, and turn the thermostat up some more, 105 degrees minimum. First tech the right numbers gets a pizza slid under their test chamber door on Saturday."

 

[AV8TOR]

I normally take manual inconsistencies with a grain of salt. My performance and signs of high pressure are what I look for. Today however I came across a difference that raised my eyebrows more than usual. I shoot w231 powder and have loaded it in the past with my Colt 1911 45 ACP and 9mm and most recently in my G19 9mm. I am looking right now at 124gr bullet data. Winchester/Hodgdon website shows 3.9-4.4. Speer shows 4.0-4.5, ok pretty much the same. I recently looked at Hornady for the first time and it shows 4.7-5.3, now that is pretty different. I have read of many settling in on a 4.8gr for their favorite load. Looks like I have more experimenting to do.