Difference in powder lots

[fouled bore]

I worked up a load using shooters world tactical rifle powder for 223 Remington. I am using mixed brass and the extreme spread is not bad, less than 70. I changed lots of powder and velocity dropped over 100fps. I had to increase the charge by .8 grains to get the velocity back up in the range I need. I am not seeing any over pressure signs, primers look good and no extractor marks.
I have not seen a change in velocity like this before by just changing lots of powder. Looking to see if anyone else has seen anything like this.

 

[climbnjump]

Pretty much anyone who has reloaded for any longer period of time has experienced this. It is one reason for the rule that when changing lots of power for an established load, you should reduce the charge and work back up.

ETA:
Some powders are more susceptible to this than others and powder manufacturers are sensitive to the issue. It is one reason why they will say about their newer powders, "Excellent lot-to-lot variability".

 

[Hooda Thunkit]

Sure. Not with that particular powder, but I have seen lot variations.

I recall that in cannister powder manufacturing, the makers aim for less then 5% variation.

New lot, new workup. That's why, when competition shooters find a good consistent load, they buy several jugs of the same lot.

 

[243winxb]

Lot to lot difference test . https://apps.dtic.mil/docs/citations/ADA572333

Click link to "Full Text"

 

[frankmako]

i have seen it with several different powders/brands over the years. one reason i buy 8 pound jugs.

 

[markr6754]

I’ve examined a number of my powder bottles and larger jugs. The majority do NOT have lot numbers, manufacturing dates, or any other detailed information to separate one from another. I have 2 8lb jugs of Universal, and there’s no markings at all. I remember scouring every mm of surface area looking for anything to give me a born-on, or bottled, or manufactured date. Mainly, with all of my initial issues with the 1st 8 lb jug, I wanted to contact Hodgdon with questions. I never did as I had no way to identify the powder, aside from when and where I purchased it. Thankfully, it manually trickles without issue, aside from loading speed, and my loads are really precise.

 

[sparkyv]

Wow, there was sigificant lot to lot variation reported in this work!

Lot to lot difference test . https://apps.dtic.mil/docs/citations/ADA572333

Click link to "Full Text"

 

[Charlie98]

I’ve examined a number of my powder bottles and larger jugs. The majority do NOT have lot numbers, manufacturing dates, or any other detailed information to separate one from another. I have 2 8lb jugs of Universal, and there’s no markings at all. I remember scouring every mm of surface area looking for anything to give me a born-on, or bottled, or manufactured date. Mainly, with all of my initial issues with the 1st 8 lb jug, I wanted to contact Hodgdon with questions. I never did as I had no way to identify the powder, aside from when and where I purchased it. Thankfully, it manually trickles without issue, aside from loading speed, and my loads are really precise.

I find that a little odd... every one of my powder bottles has some sort of lot number. I did find, on some of my older bottles, instead of the lot printed on the label (like it normally is, now) or stamped on the bottle (which can fade over time,) are what I call price tickets. In my case, orange tags that used to come out of price guns at a grocery store and such... but also subject to falling off or other deterioration.

I worked up a load using shooters world tactical rifle powder for 223 Remington. I

.

If I'm not mistaken, isn't Shooters World powder pull-down powder, or surplus manufacturing powder? In that case, every lot would be blended individually to achieve whatever pressure and velocity target they wanted for a particular cartridge they would be loading... so there would be absolutely no consistency between lots. It is not canister powder like we normally buy in 1-8# cans.

 

[Texas10mm]

Shooter's World powder is new manufacture powder.

 

[Charlie98]

Shooter's World powder is new manufacture powder.

Okey dokey... I didn't know. Seems like there is a lot of surplus powder running around...

Considering that, I don't know that I would continue to use that powder if there is such a big variation between lots. Thank goodness it looks like it produced less pressure... not more.

 

[jmr40]

When I buy powder I use a sharpie to record the date purchased. This helps me use up the powder I've had the longest 1st. That doesn't necessarily mean when it was manufactured, but it should be close. Most of what I use doesn't stay on shelves long enough to get old in the stores and I usually use it within a year or 2.

Also when I get down to the last 1/4 of powder in one container I pour it into the next container and spend several minutes shaking it to mix the 2 together. This helps reduce the lot to lot variances. I've never noted a significant difference between lots of powder. But I'm sure it can happen.

 

[Hondo 60]

Also when I get down to the last 1/4 of powder in one container I pour it into the next container and spend several minutes shaking it to mix the 2 together.

Yup, this is exactly what I do too.

 

[Dudedog]

Some powders are better lot to lot than others.
I seem to recall that powder makers try for less than 5% variance lot to lot.
But even at 5% you could have lot A which is 5% slower than average and lot B which is 5% faster than average for a total swing of 10%.
So if you had been loading MAX charges with the slower burning lot A and didn't work up again like you should loading the same MAX charge with lot B could be bad news.

 

[Texas10mm]

Some powders are better lot to lot than others.
I seem to recall that powder makers try for less than 5% variance lot to lot.
But even at 5% you could have lot A which is 5% slower than average and lot B which is 5% faster than average for a total swing of 10%.
So if you had been loading MAX charges with the slower burning lot A and didn't work up again like you should loading the same MAX charge with lot B could be bad news.

I've been able to talk to a couple of engineers from the powder companies.

A 5% lot to lot variance doesn't mean -5/0/+5 It means -2.5/0/+2.5. Your explanation would be a 10% variance.

 

[fouled bore]

If I'm not mistaken, isn't Shooters World powder pull-down powder, or surplus manufacturing powder? In that case, every lot would be blended individually to achieve whatever pressure and velocity target they wanted for a particular cartridge they would be loading... so there would be absolutely no consistency between lots. It is not canister powder like we normally buy in 1-8# cans.

That I have not heard. I take it that it is new powder.

 

[Dudedog]

A 5% lot to lot variance doesn't mean -5/0/+5 It means -2.5/0/+2.5. Your explanation would be a 10% variance

True, I heard (but don't know) 5% and assumed 5% from the target burn speed, 5% total is a lot better. (but still enough to cause grief if you don't re work up on max loads)