Mixing powders

[Unclenick]

This is exactly what the factory does when finishing up one batch and going to the next.

Where did you get that idea?

Hodgdon's manual says they keep their Australian-made Extreme powder line burn rates to ±3%. If you develop a load with a lot that is 3% low, then buy a lot that is 3% high and make up the same load, QuickLOAD shows a 168 grain .308 load of H4895 would see the peak pressure increase about 11%, which is within SAAMI limits for round variation within a lot that averages their maximum pressure number, but would easily cause sticky bolt lift and other pressure signs in a gun being loaded near maximum. Since the gas quantity is the same, muzzle pressure in a standard rifle barrel doesn't change much and the total effect on velocity is only about 2.4%. But still, that worked out to over 60 fps in the load I was playing with. This is an instance in which a chronograph would give you a heads up about possible pressure change effects. Of more interest to most target shooters is the change in barrel time was over 4%, which is enough to move you off a sweet spot.

 

[243winxb]

Take 3 different lots of powder. .Set a powder measure to a set volume. Compare weights from each, after settling the powder.

Had 3 cans of IMR 4895 bought around the same time. One rusted out the can. Sure glad i didnt mix the 3 one pound cans.

 

[Nick_C_S]

I'd figure just leaving them unopened in an ammo can will keep environmental influences to a minimum, so that's what I'd do, and open them as needed.

From Unclenick; post #8; first paragraph; last sentence.

. . ^^ Says it all for me. ^^

 

[noylj]

First, folks cuss me out when I try to explain that you need to do some minimal load work-up when the lot number changes and then folks think that mixing 2400 with 2400 will cause your gun to blow up.
So, if you don't need to do load work up on a new lot of powder, there can be no problem with adding some of the old lot to the new lot.
Or, you accept that load work-up is needed for a new lot of powder and you would never mix an old lot with a new lot.
Personally, I have found lot variations that have required an adjustment to the charge weight and I have successfully mixed a small amount of powder A into another container of powder A, but we are told NOT to so—so, don't do it.
I notice that many powders are made up of at least three different sized kernels, so every time I pick up a powder keg, I start to mix the powder in the keg (I turn the keg over and over and side-to-side, as i don't want all the small kernels to collect at the bottom).

Powder is made in batches and the batches get blended together to make a lot.

 

[Metal god]

I mix the last little bit of one pound into the new one pounder all the time . I then blend the powder thoroughly . I also write mixed lots and the other lot number on the new can just in case a recall or something so I can identify the bad lot . I'll add these are always cans that will be used rather quickly .

I how ever have a additional question to this . I've only done it with rifle powders ( IMR 4895 , 4064 , H335 etc ) I've not used enough of any one pistol powder to blend together yet although I do have an HS-6 that is just about gone . Would the faster burning pistol powders be less conducive to blending ?

 

[Stats Shooter]

I think mixing powders is just like everything else in reloading. If you are operating well below the max safe pressure, and pinpoint accuracy isn't a huge concern, then it really doesn't matter. As one poster below said, unless you re-work your load every time you get a new lot, you are essentially mixing powders already.

On the otherhand, if you are up near max safe pressure, you need to re-work your load with every new lot AND you shouldn't mix powder.

So from a safety standpoint, it depends, but from an accuracy standpoint, I always tweak my load with a new lot of powder where I go a few tenths below the old load and do a short ladder test again.

 

[Tomas]

I mix different powder batches all the time, as long as it's the same type of powder, nothin' to worry about, been doing it for 30 years. When I was learning to hand load in the Marines for our M21s and bolt action rifles, we did it all the time.

 

[Nick_C_S]

I think when we're talking canister grade propellants, many of the practices we're reading here are acceptable. Unclenick does point out a possibility based on a scenario of extremes - showcasing the importance of always being aware of the characteristics of each batch of ammo produced.

I mix the last little bit of one pound into the new one powder all the time.

I do this in the hopper. It's the closest thing to mixing propellants that I do. As I'm nearing the end of a # of powder, I run the hopper darn near empty (it's amazing how my 32-year-old RCBS Uniflow continues to throw consistent charges when there is next to no powder remaining in it), then add a little of the new # to "purge" the old. When it's almost empty again, I'll then add more of the new to finish the batch of ammo. I note accordingly in the ammo log book. Also noteworthy is that I only do this practice of transitioning from one # of powder to the next with range level ammo - stuff that is nowhere near max pressure. (I only load for pistol, btw.)

And while we're on the subject; I've been meaning to mention this here on TFL for some time now:

It has been my observation - on numerous occasions - that the new # of propellant is always slightly more dense than the old; even if they were from the same lot number and purchased at the same time. Without fail, when I throw a charge with the new powder - using the hopper preset from the old - it will throw slightly heavier than the old. It would seem that opening a # of powder (many times throughout the course of its use) has the effect of "drying out," for lack of a better term, and becoming less dense.

 

[t45]

Another vote for keeping them in unopened 1lb containers and not mixing. In my mind, the less you introduce the powder to outside elements the longer it should last.

 

[Metal god]

So what's the consensus of mixing one oz of one lot into 16oz of another that was designed to burn the exact same . How much difference ( if blended well ) can that one once effect the burn rate of the other 16oz . Again using the same powders that were made to burn the same as each other .

I always thought anything in rifle powders in 308 sized cases . The worst you'd see would be the equivalent of a 1 or 2 tenths charge difference at most . Nothing that would be noticed and very unlikely to be dangers . This thinking is why I asked the question about pistol powders . If you have a .2gr difference in some hand gun powders it makes a big difference while in a 270 .2gr is unlikely to be noticed .

Is the type of powder the factor or even the faster the burn rate the less you should combine different lots ?????

 

[243winxb]

Out of 3, only 1 pound goes bad. Sure glad i didnt mix them.

[/URL][/IMG] (my photo)

Different lots bought around the same time.

 

[Unclenick]

Yes. This N140 was moved to the plastic container (clean) from a factory container my dad got as a sample. After finding this, I checked the container at his house and it was fine. What set off the deterioration here? I don't know. More lid moisture permeation maybe. It was in a dark basement, so light damage wasn't involved. The powder grains inside were glued into a sold mass. Distilled water I added to ensure against spontaneous combustion of it immediately turned yellow. Finally decided it was safe to dig the powder out and bury it.

I've also had the experience of having surplus cartridges go bad, but only some of them, while the others seemed to hold up just fine. All same lot. And, they were only about 10 years from date of manufacture when it happened. Gee, don't you just wonder why they were surplussed out?

So what's the consensus of mixing one oz of one lot into 16oz of another that was designed to burn the exact same .

Impractical because of the roughly $20,000 in laboratory charges to have it determined that they do, indeed, burn the "exact same" way.

If the powders are different types, even if the burn rates are the same at one pressure range, they may not be at another. John Feamster did an interesting experiment showing this in the mid 1990's. He loaded 180 grain match bullets in .308 Winchester to several matching velocity pairs with IMR 4895 and IMR 4064. At 2200 fps, it took less 4064 than 4895, indicating it was faster burning. At 2400 fps the charge weights were about equal. At 2500 fps it took more 4064 than 4895, indicating that at that pressure it was now the slower burning powder. But if you look at the Hodgdon data, you don't see much difference in charge weights in that upper velocity range. Why did Feamster have it when Hodgdon doesn't? Quite possibly it is from firing at different ambient temperatures. 4064 is known for being less affected by temperature. I'd have to look his data up again, but whatever the cause, it points out that even if you successfully blended the two powders, you'd get characteristics that didn't match either under some conditions.

Then there is the problem of different packing densities. One of the other authors contributing, as Feamster did, to the 1995 Precision Shooting Reloading Guide, mentioned a load that worked fine at the range when he loaded it at home, but caused sticky bolt lift (too much pressure) if he loaded it at the range. He finally figured out that transportation vibration due to driving to the range was settling the powder, giving it a lower burn rate by leaving less space between the grains for the flame front to spread. So the question is, if you had different grain sizes and bulk densities, would they remain blended when you transported them, and if some did and some didn't, how would that affect barrel time and velocity consistency?

It may turn out these factors are all OK 90% of the time (or it may not; I have no experience with it), but I don't feel like my loads need another variable introduced.

 

[Metal god]

I was speaking only to the same powders being mixed i.e. 4895 with 4895 etc but I get your points .

Then there is the problem of different packing densities. One of the other authors contributing, as Feamster did, to the 1995 Precision Shooting Reloading Guide, mentioned a load that worked fine at the range when he loaded it at home, but caused sticky bolt lift (too much pressure) if he loaded it at the range. He finally figured out that transportation vibration due to driving to the range was settling the powder, giving it a lower burn rate by leaving less space between the grains for the flame front to spread. So the question is, if you had different grain sizes and bulk densities, would they remain blended when you transported them, and if some did and some didn't, how would that affect barrel time and velocity consistency?

This was interesting to read . I need to drive on a dirt road about 2 miles long to get to the range after driving 35-ish miles on the high way . Oh and the dirt roads is just one long road of stutter bumps . My truck rattles along like I'm in a tumbler the whole way . Unclenick brought this up before and I now put my ammo boxes on there sides rather then bullet up because of this . I had been shaking the ammo in the box before I started shooting as well but have not done that lately . It makes me wonder how much that road effects my load development ?

It may turn out these factors are all OK 90% of the time (or it may not; I have no experience with it), but I don't feel like my loads need another variable introduced.

There it is there , For all the things I do with case prep and actually loading . You'd think I'd not want another variable introduced . OK I'll stop but I do have a mixed # of H-335 I need to finish .

 

[Stats Shooter]

Deteriorated powder

This is slightly off topic, as it doesn't involve mixing but it does speak to powder deterioration.

I once bought 1,000 rounds of .223 from a small ammo maker in oregon. I had bought some .308 from them before and it was fine. I bought all of it for the brass.

Anyway, I went out to shoot it and was getting several "True" hang fires. Essentially I would pull the trigger, I could hear and feel the trigger go "click" just like a dry fire, and maybe 1/2 (+/-) a second later the round went off. So you would hear click (pause) then bang. This literally happened to 8 or so of the first 10 rounds I tried.

So at the rang I pulled a few bullets and found the powder had a very weird smell, and portions of it within the case were clumped together in some kind of gooey mess. I sent it back and they made it right, but it was strange.