What percentage variation are powder manufacturers required

As far as I know there is no law regulating things the way you state. For safety reasons and quality control each manufacturer tries to make exactly the same product time and again. They might have internal quality control standards but I cant honestly say what those exact numbers are. If I were to spitball a number I would go with +- 5% of a mean value based on the huge variation in varget discussed on line. Internal regulations to meet customer expectations is the major driver as far as I know.

EDIT -Hodgdon says they keep the burn rate to ±3% for the Extreme line of powders and ±5% for the IMR line. From post 10 below.

I don’t know of any laws that regulate powder burn rate consistency by label name. For that matter the same powder is often sold under various names.

Powder manufactures can also blend powders to alter burn rates.

I also read the variation from "standard" is 4% from 2 different publications. But I can't quote the source(s) as it was several years ago. I would rather think it's a quality control issue from the manufacturer rather than a "law"...

If the powder I purchased varied 10% from lot to lot, I'd buy as much as possible at one time of the same lot, or buy none. I use 5 grains of Bullseye for a specific load. So a 10% variation would equal loads of 4.5 to 5.5 gr. Unacceptable...

mdi said:

So a 10% variation would equal loads of 4.5 to 5.5 gr. Unacceptable...

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My thought as well. In reality, if there were product variations that huge, word would get out pretty quickly and reloaders that were in the know would avoid it like the plague.

I though I read it was 3% but I've slept a few times since I read it. Don't even recall where from.

mdi said:

I also read the variation from "standard" is 4% from 2 different publications. But I can't quote the source(s) as it was several years ago. I would rather think it's a quality control issue from the manufacturer rather than a "law"...

If the powder I purchased varied 10% from lot to lot, I'd buy as much as possible at one time of the same lot, or buy none. I use 5 grains of Bullseye for a specific load. So a 10% variation would equal loads of 4.5 to 5.5 gr. Unacceptable...

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That's 20%

https://arxiv.org/ftp/arxiv/papers/1501/1501.07163.pdf Varget.

lot to lot variations in velocity for Varget seem consistent with Hodgdon’s marketing claims.

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Link to https://apps.dtic.mil/dtic/tr/fulltext/u2/a572333.pdf Powder Lot Variations: A Case Study with H4831 – Hodgdon Extreme.. Hodgdon Extreme H4831 tested in .25-06 and .300 Winchester Magnum loads.

.It is possible that a load showing no signs of pressure with one lot of powder , might not be safe with another lot of powder. At their web site, Hodgdon recommends working up new loads when the lot number of any component is changed, and it is evident that this includes a new lot of Hodgdon

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Results Variations in average velocity (and uncertainties) for both the .300 Win Mag and the .25-06 loads with the six different lots of or powder are shown in Figure 1. Lot B had the lowest average velocity of 3122.5 ft/s in the .300 Win Mag and 2832.9 ft/s in the .25-06. Lot D had the smallest velocity variation compared with lot B at 11.9 ft/s in the .25-06 and 13.6 ft/s in the .300 Win Mag. Lot E had the largest increase in velocity compared with lot B with an increase of 111.9 ft/s in the .25-06 and 111.1 ft/s in the .300 Win Mag. Except for lot A, the increases in velocity are surprisingly similar for the a given lot in both cartridges. In fact, the velocity variations with lot number of the two different cartridges have a correlation coefficient of 0.96 (including lot A). This high level of correlation demonstrates that the velocity variations depend much more strongly on the lot number than on other factors such as bore, brass, primer, or bullet. Table 1 shows the actual mean velocity of 10 shots for each combination of load and powder lot.

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https://discover.dtic.mil

https://www.shootersforum.com/threads/h4831-lot-ot-lot-variations.186113/


See post Number 8

Hodgdon says they keep the burn rate to ±3% for the Extreme line of powders and ±5% for the IMR line. However, there were complaints in the 90's about different lots of Varget having more variation than that, and I gather that somewhere around 2,000 they beefed up their QC system and that ceased to be an issue. But if your powder is older than that, then it may have more difference than current ones do. You could always contact Hodgdon and ask about your particular lot number and tell them what you're doing.

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Why i never mix 2 different lots of the same powder, different burn rates. Another reason, 1 may be under a recall.

I have very rarely have had a 1lb can of powder be much different than the next can of same powder. I think I would notice a 5% difference. The powder company's are probabley very carful when making a batch of powder . If they let quality control go off too far nobody would buy their product. I have used powder from Hodgedon, Alliant ,Western,( Accurate) and Vihtavouri for many years and have not noticed any real diviation in perfomance for one batch to the next. I think most of us have had reloading proceduers changes that make us think it's the powder. I have also found primers to be consistant for the most part

From Hodgdon:
https://shop.hodgdon.com/sites/www/files/2020-10/EXTREME RIFLE POWDERS.pdf

EXTREMERIFLEPOWDERSTHIS EXCLUSIVE LINE OF EXTRUDED POWDERS WAS DEVELOPED WITH EXTREME CONDITIONS IN MIND.They’re manufactured so you can’t tell the difference in performance from one lot to the next. And whether you’re hunting deer in the dead of winter or prairie dogs in the middle of July, you’ll get the same consistent performance, load after load. Some would say our obsession with performance is a bit extreme. We couldn’t agree more


Now if folks want to get nit picky (which they do) Hodgdon doesn't MAKE anything. It depends on what powder and where it was actually made, here, Canada or Australia.
Those plants have been doing it a long time. It's science, they and all powders are very exact. They produce "stuff" for the Military
As they say above you will NOT know the difference in lots.Just like primers, lot to lot will not make a difference.

There is really no point to determining the burn rate powder manufacturers make their powders vrs canister grade powders used by hand loaders.

Powder manufacturers make smokeless powder and sell it in bulk, primarily to ammunition manufacturers. These are not canister grade powders at this point like what is sold to hand loaders and the variation in the lots of powder are greater than what is found in canister grade powders. This is OK for commercial and military ammunition manufacturers because they do not load their ammo like a hand loader does. Ammunition manufacturers have their own laboratory that determines the bulk powders burn rate and pressure characteristics for each batch or barrel of powder and what charge setting to use when loading ammunition with it. Powder along with bullets, brass and primers go into a large machine and the powder charge is set by the laboratories determination. In a manufacturing plant its likely that several machines will be producing the same ammo using different charges in each machine with the same bullet weights.

The canister powder companies which may or may not manufacture power but sell to hand loaders get bulk powder from the powder manufacturers. They have their own laboratories who's purpose is to make powders for hand loaders that have a consistent or normalized burn rate and pressure characteristics to a standard set my the particular company. This is what allows hand loaders to use the same load data year after year for the same name powder. How they do this is a bit different than what ammo manufacturers do. These companies have several batches of the base bulk powder with different burn rates as characteristic of bulk powder deliveries. They then blend powders of different burn rates to "normalize" the burn rate to the companies standard and this is what they package and sell.

Exactly why it has always been published that if you change ANY component in a load that you've developed, back off and work back up to it.

kelbro said:

Exactly why it has always been published that if you change ANY component in a load that you've developed, back off and work back up to it.

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Yep, and every owners manual I have ever read for a new gun tells us to never shoot "reloads" in them.

Most every thing I have read in this thread is anecdotal. Only thing from a manufacturer is this...."

Rule3 said:

They’re manufactured so you can’t tell the difference in performance from one lot to the next.

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Hmmmmm, what to believe, a powder distributor or a random person on the internet?

243winxb said:

Why i never mix 2 different lots of the same powder, different burn rates. Another reason, 1 may be under a recall.

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The powders you have are not from one batch, they are several batches blended together by the manufacturer/distributor to get the desired burn rate for a specific lot. Any small difference between two lots of those blended powders will be lessened by blending them. Period. It will not increase or decrease the spread, only reduce it. If you have already shot 7 1/2 pounds of a 8# jug of recalled powder, will blending it in
8# of good powder make it less or more dangerous? That 8# jug that you opened a year ago and has sat half empty has broken down because of the half a jug of air in it and has changed it's burn rate more than the difference in any two lots on the store shelf. You scale with accuracy of +/- .1 gr and your powder thrower will make more difference in your batches of ammo than a difference in powder lots. For some powders, difference in ambient temperature when shooting will make more difference than the difference between two lots of modern powder.

Again, most everything here is the opinions of folks. These are mine derived from years of experience with the powders I use. I do what makes me feel comfortable and safe. I suggest others do the same.

Hodgdon does not manufacture the powders they distribute.

Do your own testing, as always.

AJC1 said:

That's 20%

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My thinking was 10% of 5 grains is .5 grains/ So 10.% less than 5.0 is 4.5 gr, and 10% more is 5.5... But the last mathematics I did seriously was in an Electronics 101 class in 1988...

I read a post saying +/- 10%.

buck460XVR said:

That 8# jug that you opened a year ago and has sat half empty has broken down because of the half a jug of air in it and has changed it's burn rate more than the difference in any two lots on the store shelf.

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Now.... that's a test I'd like to see.

Following that logic, and assuming the continued deterioration...or perhaps 'change' would be a better term... with powder that is 10, 20, 50 years old would be completely off the reservation as far as burn rate.

Seems that it is and should be less about legality and more about product liability. Since makers are making ammunition to an internationally recognized specification (SAAMI) then they would be liable for damage and injury for producing ammunition outside of that spec. By nature, nitrocellulose based powders vary in burn rates based upon pressures and a 5% swing in volume can produce huge pressure spike well outside of 5% pressure change. I would think it very difficult to write a law mandating any maximum percentage of change or giving any range of fluctuation. More likely they expect manufacture to given standards with civil liability driving the bus and criminal negligence as a backup option for grossly out of spec product likely to cause injury that is knowingly and willingly produced and sold on open market.

WestKentucky said:

I would think it very difficult to write a law mandating any maximum percentage of change or giving any range of fluctuation.

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Shhh!!! Don't give them any ideas...

Charlie98 said:

Shhh!!! Don't give them any ideas...

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The laws they would be most interested in now would be removing our ability. It most likely fall in the explosive storage requirements ie primers. Lest I digress further

Take it for what it's worth. I seem to recall Lee's Modern Reloading 2nd Edition as stating powders can vary as much as 3% lot to lot.

One test with two rifles that perhaps only 2% of shooters would even care about.??

They seem to dismiss that other brand of primers and or brass and bullet may make a difference.??

Statistics, bars graphs can be published in such a way to "prove" anything

Do another test, use different rifles, primers, brass and bullet and all the numbers will be different

https://apps.dtic.mil/dtic/tr/fulltext/u2/a572333.pdf

The disclaimer:

Discussion
Thehighlevelofcorrelationbetweenresultsforthetwocartridges suggeststhattestinglottolotvariationsinpowderperformanceinonecartridgeandriflehasagoodchanceofaccuratelypredictinglottolotvariationsinothercartridgesandrifles.

IMO. I think powder manufactures govern them selfs pretty well. Primer makers also. I think it's great that we deal in an activity where manufactures care about product image and customers.