Data discrepancy

R

reynolds357

New member
Sierra in their paid app lists two 140 gr bullets with imr4955. 53.7 and 53.9 are the max loads.(270 win)

Hodgdon lists a 140 gr bullet, starting load is 54 and max is 59 gr.

Granted, bullets are not identical, but dang close. I am use to discrepancy, but never seen anything this huge.
 
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It happens in the bullet company manuals. Hornady has some as much as about 9% below what the powder company puts up. I believe it is caused by the use of production guns to develop the load and then having only the highest load they develop that way tested, reducing the load if it is too high, but not upping it when the result is low. Also, they use powder bought off-the-shelf, which might be on the low or high end of the burn rate tolerance, where Hodgdon has access to data powder that is at the nominal burn rate for the type.
 
These days max loads can be very "optimistic" on their pressure ratings--I routinely verify all published data in quickload if at all possible. I'm often left scratching my head at the discrepancies, but more often than not quickload is the better predictor between the two.
 
Cross check with a 3rd and 4th reference .... sometimes the descrepency will show up when three manuals say X is max and one says 2X is max...go with the three that agree.

If you can't get three or four referances to cross check with always go with the lighter loads . Rule #1: start low and work up slowly to a max. charge .
Gary
 
Sometimes manufacturer "A" will test a load and when they achieve the results they are looking for they simply don't keep going any farther to see what happens. Manufacturer "B" will take the same load and continue testing with more powder until they reach the true max load.
 
jmr40 said:
Sometimes manufacturer "A" will test a load and when they achieve the results they are looking for they simply don't keep going any farther to see what happens. Manufacturer "B" will take the same load and continue testing with more powder until they reach the true max load.
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In this instance, Sierra has their loads noted as "high pressure loads". A "high pressure load" below Hodgdons starting load. Someone has to be wrong.
 
gwpercle said:
Cross check with a 3rd and 4th reference .... sometimes the descrepency will show up when three manuals say X is max and one says 2X is max...go with the three that agree.

If you can't get three or four referances to cross check with always go with the lighter loads . Rule #1: start low and work up slowly to a max. charge .
Gary
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I cant find any other references. Thats a pretty new powder.
 
If you have access to a chronograph, you can use it to load up to the velocities that the data says to expect. Then if you don't encounter signs of excess pressure before you get to top book-velocity, you can use the velocity itself as the indicator of the maximum charge weight, adjusted for barrel length, of course.
I agree, when I see grossly conflicting data, it does kinda raise my eyebrows. Makes me wonder if a novice handloader might blindly trust the data that can't be quite right and maybe get some alarming results.....:eek:
 
Pathfinder45 said:
If you have access to a chronograph, you can use it to load up to the velocities that the data says to expect. Then if you don't encounter signs of excess pressure before you get to top book-velocity, you can use the velocity itself as the indicator of the maximum charge weight, adjusted for barrel length, of course.
I agree, when I see grossly conflicting data, it does kinda raise my eyebrows. Makes me wonder if a novice handloader might blindly trust the data that can't be quite right and maybe get some alarming results.....:eek:
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There is some wacky data out there.
 
There are many variables that can account for the variation. In addition, my recent inquiry to Sierra asking whether their data was pressure tested went unanswered.
 
I saw something similar last year with some 270wsm data. Where Sierra's Data had a max charge lower than Hodgdon's Starting load. In my particular instance I found resultss that gived pretty well with Sierra's data. Oddly enough From 70 grains of H-1000 all the way to 73 grains of H-1000 I saw less than 10fps gain in velocity. With Accuracy being the best at 70 grains (Hodgon's) start load. I figured that was thanks to the 22 inch barrel and just not having enough barrel time to burn anymore powder than I was already.

Interestingly the Sierra max charge of 69.4 grains had an advertised velocity of 3275, At Hodgdons start load of 70 grains I was getting 3305 with stunning consistency. Less than 10 fps es over a 20 shot string. I can see .6 grains giving 30 fps so in my instance the Sierra data was basically spot on with my own results. Although the Hodgdon data's max charge was pretty dang hot with no increase in velocity. I was also besting Hodgdon's maximum velocity by 150 fps with a shorter tube and 3 grains less powder.

Sierra's data for most of their loads list a universal receiver. I would hope if they have a universal receiver they also have it set up to test pressures from their testing. I also wonder if in that case Sierra saw that they were not increasing velocity with charge weight so they maxed out there data at the bottom of that velocity node when Hodgdon kept going to a certain case volume.

Anyway, sorry I went on a rant there. Didn't mean to sabotage your thread. It is my opinion that Sierra data is pretty good. At least my results have been very consistent with theirs over several setups.
 
Load data discrepancy has a negative effect on my confidence in their process. An example is comparing Hodgdon to Nosler for the 6.5 Creedmoor 130 gr Accubond. Same primer, same brass, but Hodgdon publishes powder charges several grains less than Nosler. And the velocities are a couple hundred fps less as well. Hodgdon data for heavier bullets shows powder charges and velocity significantly higher than their data for the 130 Accubond. Makes a feller scratch his head. :confused:
 
In this instance, Sierra has their loads noted as "high pressure loads". A "high pressure load" below Hodgdons starting load. Someone has to be wrong.
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Why?

Load data discrepancy has a negative effect on my confidence in their process.
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I can understand why you might think that, but the reality is that discrepancy between different sources should give you a positive feel about their process.

This is because of the simple, yet frequently overlooked fact that the things being tested are SIMILAR but NOT IDENTICAL.

Even if great care is taken to make them as close to identical as possible, THEY WILL NOT BE IDENTICAL.

everything has tolerances. They combine in slightly different ways even when effort is made for all things to be the same. They are shooting DIFFERENT GUnS with DIFFERENT barrels, and odds are really high the brass, powder, primer and bullets are not all from the same batch.

Ever see a load shoot fine in one gun and have sticky extraction in another, despite being chambered for, and shooting the SAME ammo? I have.

seen loads crater primers in gun A and not do it in gun B. It is ENTIRELY possible to get a "SAAMI MAX" pressure load in one gun and be either above or below it, in another, using the same ammo. And when your ammo is different, the variables increase.

Ever see two "identical" guns same everything, shooting the same ammo, give different velocity readings? Same thing. Guns are SIMILAR so reloading data is a useful GUIDELINE, but they are not IDENTICAL, and you simply should not expect them to be.
 
A "high pressure load" below Hodgdons starting load. Someone has to be wrong.
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I've seen this too, and when cross-verifying with quickload and recorded labradar velocities knew to back off. I think you have a valid point. One thing I've noticed (using 350 L data from them) they might also vary the COL dimensions across different loads that don't necessarily work in all types of firearms and may not even fall within the bounds of SAAMI specs for the cartridge dimensions.
 
With all the variables and tolerances in:

* barrel chamber, bore and groove dimensions
* firing pin strike force and primer dent depth
* barreled action's resistance to recoil
* case neck grip on bullet (force needed to push bullet forward)
* powder lot burn rate
* primer flame properties
* chamber pressure and muzzle velocity measuring

Muzzle velocity and chamber pressure data across several rifles with a given load will have a big spread. More than 100 fps and 5,000 psi is normal.
 
Double and triple plus to 44AMP's and Bart's posts. And there's more:

Notice how Sierra and Lyman data both list which load produced the best accuracy. Sierra also lists a hunting load that has the highest optimal velocity for expansion within its expected impact range. Ask yourself, why are all the other powders still listed if the best loads have been found? Well, people may want to use what they have on hand or may be unable to get the exact powder listed. So a bunch of sub-optimal powders gets listed, too. Additionally, the powder lots have tolerance, and they have to come up with a recipe that is safe for all lots within that range, including the fastest burning one, so they need some way to allow for the pressures to differ due to that, even if the gun and case and primer and bullet match their test choices.

One of the things that happen with sub-optimal powders is pressure, and velocity variation can increase, even before the lot-to-lot variation is considered. A manufacturer following the SAAMI methods will strive for a target velocity and then check that his load's average pressure does not exceed that SAAMI MAP (Maximum Average {peak} Pressure), that his pressure standard deviation does not exceed 4% (for rifle; 5% for centerfire handgun loads) and that the extreme spread between the highest and lowest pressures measured in a 10 round sample do not exceed the SAAMI MEV (Maximum Extreme Variation) number. Working with a range of sub-optimal powders doesn't let you observe all those niceties, plus they have to allow for lot variation, so the solution used by Hodgdon and Lyman and others is to pretend the SAAMI MAP value is an absolute limit for a sample of 10 rounds rather than an average. Thus, they set the load such that the highest value in the extreme spread of pressure does not exceed the SAAMI MAP, thereby creating the load data's own MAP that is lower than SAAMI's. This is why the pressures listed for the maximum loads of different powders are not the same and not at the SAAMI maximum. That the exact peak value they would get varies by 10-shot group also accounts for a lot of the discrepancy between different load data source's idea of maximum.

The illustration below shows how the same SAAMI standard test of .45 Auto pressures with random peak pressure value would be handled by a manufacturer vs. a load manual author. (Incidentally, this method of determining the peak is described in the last Hodgdon print manual I bought around 2004 or so and is not something I've ascertained independently. Hodgdon even said to note this means the powder they list with the highest maximum load pressure is the one that produced the most consistent pressure and velocity in their tests.

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Anecdote Warning:
"Working up" loads is not a major activity for me. My usual .308 load was copied from a friend. It is very accurate. He moved on to heavier bullets and heavier loads at the expense of brass life, I didn't. My .22-250 loading showed primer effects - H414 demands magnum primers, supposedly identical W760 does not - but other than that, straight out of the book shoots well.

I did ring the changes on .223 trying to make it into an FTR, 6.5 twist + 90 gr bullets.
But when Sierra said a load was maximum for that combination, they meant it.
The Sierra maximum load(s) would not get a 90 gr SMK to 1000 yards supersonic.
So I souped them up. There were no "pressure signs" on rifle or brass but I started losing bullets; they were deforming from too much powder behind a long skinny bullet.
I changed to JLK VLD and tried Berger VLD. I could overload them as required. Still didn't make the .223 a 1000 yard gun, but it is a fine midrange rifle.
 
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