Minimizing powder variation - lot to lot

[psmith]

Okay here's the deal. I have been buying powder when and where I could just to stock up. Nobody had any 8lb containers and I'm stuck with a bunch of lb containers. Once I get a good load, how do I keep it when changing containers?

I have thought about containing all the separate containers into one but was concerned about static buildup and how to seal everything.

Or do I not worry about this and just run a couple of loads over the chrony for each new batch and keep the velocity consistent?

 

[427Cobra]

Re: Minimizing powder variation - lot to lot

The easiest and best to reduce powder variations is to buy it by the case, I would find hard to beleave that Powder Valley is always out of the big jugs of the powder your using.

I have no problems mixing the same powder from different jugs together, just redo load development to ensure safety.

 

[redbullitt]

Re: Minimizing powder variation - lot to lot

I try to buy the same lot for simplicity, but that is not always an option. I go the mixing route if that is the case.

Some powders are much more variable than others. If I am using surplus stuff I always make a mix of jugs, but h50bmg and varget have been very consistent for me (and I usually dont bother to mix).

If you are buying normal powder, ie hodgdon or VV etc, you should be fairly consistent and ok unless you are really really shooting for consistency or are running a hot load that you cant afford to increase pressure in.

 

[rpk762]

Re: Minimizing powder variation - lot to lot

When I am forced to buy 1lb jugs. Sometimes they just do not have 8lb jugs. Sometimes you will get a bunch of powder from many different lots. I must be the unlucky one. I shoot Varget in many different rifles and I have noticed that each lot can be very different. What I do is never toss any 8lb containers. I then poor about 6 lbs into the container and put the lid back on. Then slowly I end over end the container. Then when it is on its side I slowly role the container that way. Then go end over end. I do this slowly each way as many as 5 times and as few a half a full rotation. I keep doing that until I feel it is mixed.

I do that for every power I use. The reason is I was having some problems dropping charges for a 223. Each drop was as much as .5gr off high or low. I did not know what to do so I put all the powder in the container and it hit me. Product may have settled during shipment you know what you would see on a box of cereal. That is when I did the above and then every drop was less than .1gr variation. I can live with that.

 

[psmith]

Re: Minimizing powder variation - lot to lot

That sounds like an idea. I'll invest in an 8lb'er and use that to mix everything up. Just wanted to make sure it was safe mixing it all together.

 

[1lnbrdg]

Re: Minimizing powder variation - lot to lot

I purchase powder in the 8lb jugs. My last purchase was for 6 jugs. When I got it home, started mixing them all together so for the next 6 jugs the load will always be the same (depending on how long my barrels last).

I work in a plant that makes extrudate and sphirical pills for catalysts. To blend them, they are pour'd thru a big hopper, a funnel if you will. I have a couple of 5 gallon HDPE plastic jugs I mix by pouring from 1 to the other a couple of times, maybe more if I'm feeling more anal than normal.

 

[Fred_C_Dobbs]

Re: Minimizing powder variation - lot to lot

Unless you measure individual charges by volume or you live in the desert, your charges will become less powerful over time. This is because powder absorbs humidity from the air and, over time, a given volume of powder will weigh more (due to the weight of the water). This means a given charge by weight will contain less power.

The last new bottle of powder I opened was a 1# bottle of Varget. It was the same lot#, bought at the same time and stored in the same place as the 1# bottle it replaced. My MVs with the new powder increased ~30 fps. And this change was consistent with the several bottles of powder I have checked in this way. This effect will be more pronounced the more often the bottle is opened and longer you take to empty it.

So I always chronograph my loads with a new bottle and "recalibrate" my MV, and sometimes in between.

 

[The Mechanic]

Re: Minimizing powder variation - lot to lot

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">Unless you measure individual charges by volume or you live in the desert, your charges will become less powerful over time. This is because powder absorbs humidity from the air and, over time, a given volume of powder will weigh more (due to the weight of the water). This means a given charge by weight will contain less power.

The last new bottle of powder I opened was a 1# bottle of Varget. It was the same lot#, bought at the same time and stored in the same place as the 1# bottle it replaced. My MVs with the new powder increased ~30 fps. And this change was consistent with the several bottles of powder I have checked in this way. This effect will be more pronounced the more often the bottle is opened and longer you take to empty it.

So I always chronograph my loads with a new bottle and "recalibrate" my MV, and sometimes in between.</div></div>
I have always thought about getting a small bottle of dry nitrogen and giving it a little soft blast into the bottle before sealing it back up. Just never followed through with it.

 

[Fred_C_Dobbs]

Re: Minimizing powder variation - lot to lot

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">
I have always thought about getting a small bottle of dry nitrogen and giving it a little soft blast into the bottle before sealing it back up. Just never followed through with it. </div></div>
I was using QuickLoad and OBT to work up a new load from an 11-month old bottle of RL-19 and the chrono numbers just weren't making sense. I asked one of my reloading mentors about it and he suggested my powder had gained a substantial amount of water weight, which could account for my bullets being so slow. Sounded like bullshit to me but just for shits and giggles, I put a packet of silica gel desiccant in the bottle and left it.

The next day, I loaded up a handful of rounds and chronographed them. The same charge weight was 70 fps faster. So I let it dry out for another day. Day two, I loaded up another handful of rounds and chronographed them. They were 96 fps faster (despite the weather turning 15°F cooler) and I got the first hint of a stiff bolt lift. The next day, I was afraid I was going to overpressure the rifle so I reduced the charge weight but ran the chrono numbers through QuickLoad to determine the powder's new "burn rate factor."

It took five days altogether before the increase in velocity leveled out. I started out getting 3022 fps from 44.2 grains. When it finished, 41.4 grains was getting me 2992 fps. Somewhere along the way, my RL-19 had absorbed a bit more than 6% of its weight in humidity.

So now I put a packet of silica gel desiccant in every bottle of powder at least a week before I first use it. Then I chrono a few test rounds to account for differences in lots. I figure if I reduce the water weight to nil from day one and keep it there, that's the best consistency I can hope for.

The silica gel packets are cheap. Most new electronic goodies come with a decent sized packet in the packing that can be put to use. And they're re-usable/re-chargeable. Two hours in a 250° oven and they're good as new. The only thing is the free bags are sealed with glue so heating in the oven might make the seams come apart. Just give 'em to Panty Six and have her sew a seam on the three sealed sides with cotton thread and you're in bidness.

 

[Fred_C_Dobbs]

Re: Minimizing powder variation - lot to lot

psmith, sorry to (seemingly) go off-topic but that drivel all goes to the (obvious) point that I think the prudent thing is test every new container of powder and tweak your charge to get back to the old MV.

 

[Tripwire]

Re: Minimizing powder variation - lot to lot

Using a true Optimum Charge Weight incorporates a tolerance into the load per slight pressure variances...which, if a consistantly precise charge weight is a constant, goes a LONG way towards mimimizing lot to lot powder variations.

 

[psmith]

Re: Minimizing powder variation - lot to lot

I never thought about the water absorbing thing. I always try to seal everything up but it makes sense. So sounds like I should get some chrony data now that I have a good load and try to keep that consistent. I'll also try the dessicant packs. I was playing with exbal tonight and a 25 fps difference gives about .5moa at a thousand yards.

 

[The Mechanic]

Re: Minimizing powder variation - lot to lot

I will have to give the silica gel packets a try

 

[JeffP40]

Re: Minimizing powder variation - lot to lot

If you are having trouble finding 8#ers, can you get your local supplier to add your order to their next powder order? That way, you would not have to pay the HAZMAT on your own. You might have to wait a while, but it would ensure you get what you need.

 

[BigMahi]

Re: Minimizing powder variation - lot to lot

+1 on the water absorption effect. I found this out measuring powder using a fixed Lee scoop. The same 3.1cc volume of powder weighed more after the container was open for a while.

It seems to get the most consistent charge for awhile, theoretically requires:

1. purchasing a case of 8lb jugs.
2. pour all the powder you just bought into a 5 gallon bucket.
3. roll 5 gallon bucket around for some reasonable time to achieve consistent mix.
4. segregate powder back into jugs.
5. throw same # of silica packets in each jug. Roll it around.
6. wait a few days. roll each jug some more.
7. reload as many rounds in each session to minimize exposure, rotating the jugs per session.
8. keep all jugs in same container/holding area.

I'm ok with buying a few 5lb jugs to save on hazmat. I don't think my skill is at where lot to lot consistency is that noticeable. To each his own I guess.

 

[BigMahi]

Re: Minimizing powder variation - lot to lot

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JeffP40</div><div class="ubbcode-body"> If you are having trouble finding 8#ers, can you get your local supplier to add your order to their next powder order? That way, you would not have to pay the HAZMAT on your own. You might have to wait a while, but it would ensure you get what you need. </div></div>

Give Powder Valley a call. Their website is powdervalleyinc.com. Their prices are great and will accommodate just about anything.

My local community did a group buy with them last year. We ordered a ton of stuff with the craziest assortments you can think of. PV topped that with free shipping as long as someone secured a loading dock somewhere. I think someone got their neighborhood hardware store to volunteer their loading dock. Lol.