Varations In Powder Lots

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kingmt

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I have heard that when opening a new bottle of powder to rework your load by starting 10% lower but 10% of the max is lower then the starting load listed.

I was loading up some 2 different bullets in .5 gr intervals of Varget & ran out of powder so I bought another bottle. While I don't know what the lot number is on this bottle they do have different numbers on them so I assume they are from different batches.

How much will this affect my test?

I did load 3 each for 2 of the same loads from the last batch of powder to see if they are the same.
 
Yes, it is correct to drop back to starting loads - or the 10% thing - when using a new lot of powder. It is MOST correct to do this when the 'old' load was at or near a maximum level.

If you are indeed beginning a new series of tests, you'll get better and more reliable results by working with one lot of powder.

If you like Varget, for instance, it is advisable to buy a four or eight pound keg to avoid this sort of thing.
 
My experience has been that powders do not vary 'lot to lot" nearly as much as I was led to believe as a rookie loader.
As Archie said, though... ALWAYS better to err on the caution side.
 
The burn rate might be slightly different in a new lot of powder, which is where the start low and work back up advise comes from.

The powder companies go through great lengths to keep cannister grade powders the same from lot to lot for safeties sake, but keeping them exactly the same all the time would be impossible.

Also, don't assume that XYZ setting on your measure will throw the same weight of powder when you change lots. Check it.
 
I always load a few rounds lighter than the load I was using from the previous lot and work up. You dont have to load a bunch just a couple in each increment up to your previous max load. Your chronograph if you have one will tell you how close the new lot is if your velocities match the velocities of the previous lot with the same charge of powder. These loads are handy for fouling shots if you have cleaned the barrel.
 
I called Accurate Arms and they told me the industry standard for the blended powders that we get, the industry standard is 10% varience (from the mean I assume), and their was 5%.

If you are loading a maximum load, any component change, brass, bullet, powder, primer, can and will cause blown or leaking primers.

If you want to see the differences of lots in print, look at your older Lyman reloading manuals.

HP-38 and W231 are the same powder. H110 and W296 are also the same powder, just sold under different brand names.


Now look at the manuals and see the differences between charges and pressures.
 
I think a re-work up of loads are probably required if you are using near max/max rifle loads for different lots.

For pistol loads, I am not too sure if this is warranted for mid to high range loads. All the years I have gone through various lots of W231/HP38, I have not reworked my loads. I just make sure the dropped charge weights are verified at the start of each reloading session. Another benefit of having a "buffer headroom" of your loads in case there is some lot-to-lot variations in powder.
 
I am new to loading rifle so everything is new. Powder, bullets, & setting depth are all new equations. Since my COL is way over what the manual says I'm not very concerned about over pressure from switching powder lots. The switch is half way between max & min. I have found that a .5 gr difference normally moves the shoot so much on the target that it is obvious it is a different load. This is why I made a few of the last batch so I could see if they were the same. I'm hopping this will keep me on track anyways.

I'm just wondering if I may miss finding a powder/bullet combo that works for my rifle by switching lots half way through the load.

If I know I was going to use that much powder I wold have bought a new bottle before I started & worked out of it or mixed the 2 together before I started. When I seen I wasn't going to have enough to finish my loads I mixed the remainder with the new bottle.
 
if your current load is 10% below the listed max in the manual, you should be ok.

murf
 
I know what they say, and I don't readily dismiss warnings about safety. But in my personal experience - so far - I haven't noticed much variation between lots of powders. But I rarely load anywhere close to max loads.
 
Funshooter I agree I normally load for accuracy not velocity. But if a load is leaning toward the hot side and is the most accurate thats what I use. I have never had an issue with lot to lot variations but I always check because I used up all my luck in my youth LOL.
 
A chronograph tells you right away.
Click to expand...

A chronograph only tells what the average pressure that drove the bullet down the barrel is.

It does NOT supply information about the peak pressure.

Average makes bullets fly, peak blows up guns.
 
Lot to lot variation is inevitable. But it's normally quite small.

If loading anywhere near maximum, I drop back a bit, but more like 2 or 3 percent, not 10 percent.

If loading 2 or 3 percent below the max already, I usually don't worry about it if using a commercial cannister grade powder. (unless, of course, the ammo shows a difference in performance)

The biggest variations, IME at least, have been with MilSurp powders. With these, I drop back the full 10 percent to starting loads every time.

Just my experience, for however much, (or little:D ) it's worth!
 
Quote:
A chronograph tells you right away.

A chronograph only tells what the average pressure that drove the bullet down the barrel is.

It does NOT supply information about the peak pressure.

Average makes bullets fly, peak blows up guns.
Click to expand...

Uh, a chronograph measures velocity, not pressure.;)

Don
 
A chronograph tells you that if your last lot of H-supermag with 34 grains of powder got 3000fps and your new lot of H-supermag with 34 grains of powder gets 3000fps they are the same. I can get the same velocities with a slower powder as I can a faster powder the difference is the faster powder will usually have a much sharper pressure curve. You are trying to make a chrono do something it cant I am using it to compare different lots of the same powder this it does excellent.
 
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As a beginning reloader I looked at that 10% too and realized I'd be under the minimum. No idea who started that nonsense, but don't do it. I drop back a few grains to start and that's it.
 
Buying IMR4895 over the last 10 years, it is so close I can't measure any difference.

The astonishing things about powder lately is seeing how high the velocity goes with 270 and Re17 in a work up, and then reading Kombayotch's temperature experiments with Varget vs Re17.

Re17 may make hundreds of fps more than I ever thought possible, but Varget is temp stable.
 
I'm just posting to let everyone know I haven't abandon this thread & I'm thankful to all that has replied so far.
 
This whole thing has me wondering if trying to work up loads for accuracy is a waste of time. For my 22-250 I have been so far using Varget exclusively and have yet to find a load I'm comfortable with,so I continue testing. If I have powder variations from lot to lot,what have I gained? Suppose I land on what seems to me to be the gun's sweet spot,but I can no longer find the same lot number,where does that leave me? I have taken the position of mixing jugs of Varget when the one I'm using is below 1/2 BEFORE loading for the range,and I always try to keep an extra fresh jug on hand. Since I keep my loads relatively low...start to just above mid-level,I can't see as though I'm taking chances. If Varget varies so much that I should start over at the minumum load,why use it at all. Besides,if I did get a "hot" jug of it,am I not better off mixing than using as-is? Is my thinking flawed? Should a reloader ALWAYS keep powder lots separate?
As for loading my 357,I usually use H110 and I'm far more careful there. But even then,with the dangers of UNDER loading it it seems to me that mixing a new jug and staying on the low side of center provides me with an extra measure of safety. Shouldn't new lots of H110 and Win 296 be tested somewhere ABOVE start load? Here's where I should be buying in as large a jug as possible and/or all of the same lot number.
 
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