measuring powder question?


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usmc0811
June 16, 2013, 10:47 PM
I'm new to reloading and have been gathering the necessary equipment to start to reload .40 cal. ammo I'm at the point where I will soon be measuring my powder using the lee powder discs. Now when I weigh my charge on the scale and it reads something like 7.045 or 7.102 or whatever and it calls for just7.0 grains would the extra 10th or hundredth make a big deal? I know ideally 7.0 on the nose would be best because that is what it calls for but how accurate does it need to be and still be safe, I'm afraid if I am over just a bit I could harm myself or do I just need to worry about double charges? Thanks a bunch for all your help I am learning a lot on this forum with all the knowledge everyone has.

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hAkron
June 16, 2013, 10:56 PM
What powder measure are you using? You mentioned disks, so I assume its a Lee powder measure. Since the holes are fixed, the trick is to find the hole that is the closest to the charge you are looking for. Will a 0.1 or a 0.01 variance have a disastrous effect? Probably not if you are loading sane loads within the range listed in a reputable, current reloading manual, or using current manufacturer provided tested information.

KansasSasquatch
June 16, 2013, 11:07 PM
My question is, what kind of scale are you using that will read down to 1/1000th of a grain? I don't believe I've see a scale that will measure that. Most go to 1/10th of a grain. Are you using an electronic scale? Are you sure you don't have it set to measure grams?

usmc0811
June 16, 2013, 11:23 PM
I have the lee powder disc to drop my charges and a lee beam scale to weigh them yeah I know it wont weigh to the .001 but I was just trying to let you know what I meant about how accurate do I need to be so as long as it don't change from 7.0 to 8.whatever I will be good. I don't plan on making any hot loads and will be sticking to the book on the low end.

Jesse Heywood
June 17, 2013, 12:00 AM
This is why you start at the bottom of the load range and work up. Then you aren't overtaken when you near the end of the tolerance band.

Conservidave
June 17, 2013, 12:29 AM
There is a lot of variables in reloading, some things you can control and some you cant. Powder measurement is one thing you can control. One tenth of a grain either way below max isn't going to hurt but once you start loading for accuracy you'll start taking everything into account, it's part of the learning process. As a new reloader it's important to take your time and follow good reloading practices and you'll be fine.

Dave,

mgmorden
June 17, 2013, 12:49 AM
Generally load data is given in a "range". Pick a listing for the measure that's supposed to get close to something inside the range you want, but understand that what the scale says is what the number actually is. If the listing says 7.0 and your scale says 7.1 then for you, that setting is giving 7.1gr of powder. If your load data says 7.1gr is save though, then you're good to go.

Understand too that powder measures typically aren't perfectly precise from throw to throw. This margin of error is greater with some powders than with others, but on a lot of them you could see as much as 0.2gr variance between throws. What I typically do is to make sure than 10 throws still average out to what I want my intended throw to be.

Depending on what type of shooting you'll be doing this may affect what you do. Long distance benchrest shooting you're probably not even going to use such a measure due to the variance. For "practical" style shooting such as plinking, loading hunting ammo, shooting IDPA, USPSA, etc, then the variance in the measure should be fine.

1SOW
June 17, 2013, 01:09 AM
Marine, Used properly, the Lee disc system will be able to drop most powders with less than .05 grain variation.
Ball, flattened ball, and small rod powders will drop extremely close consistently. Some exceptions to this will occur with large "flake" powders. but they tend to not be sensitive to larger variations.

Loads that are not at the extreme low or high end of your load data are not significantly affected by a .1 gr variation.with most common pistol powders.

The Lee beam scale is delicate to set up, but IS extremely accurate & consistent.

Additionally: the two major mistakes that cause dangerous results are "FAILING TO DROP ANY POWDER" or "DOUBLE CHARGING". Both are caused by failing to focus on what you are doing, getting distracted for just a second or two or toasting the Corps while reloading.

A really good "light" shining into the case at the powder drop, helps prevent these major mistakes.

Hope this answers your original questions.

KansasSasquatch
June 17, 2013, 02:13 AM
Like has been said .1-.2gr variance with most powders isn't going to make a whole lot of noticeable difference. Having said that just make sure you aren't starting out with MAX charge weights. If you are getting data only from powder manufacturers' websites, STOP. Get yourself a couple good manuals. Manuals give you a safe range to work up loads from. Some powder manufacturer websites only list a MAX charge, like Alliant for instance. They list the MAX and tell you to reduce it by 10% to find your starting load. So if 7.0gr is the only number they give you, multiply it by 0.9. In this case that would leave you with 6.3gr as a starting charge. Now me, personally, if loading for an auto loading firearm I pretty much never start with the minimum charge listed. They won't tend to cycle the action, so I start .1 or .2gr heavier.

There are some exceptions. If using certain powders the manufacturers will suggest only reducing the charge by 3%. I believe H110 and W296 are examples of that. They supposedly act erratically if reduced more than that. And when it comes to fast burning powders like TiteGroup, I start with listed minimum charge weights even if its for an auto loader. Fast burning powders leave little room for error.

gamestalker
June 17, 2013, 06:07 AM
For instance, some fast burning powders may have a total charging table range of only .3 - .4 grains of a grain could represent as much as 33% of the charge range, thus could create a noticeable increase in pressure. Then add into the mix that you may be charging at a max level, and maybe seating significantly deeper than what the published loads were tested at, you could end up with excessive pressures. Some cartridges are extremely pressure sensitive to seating depths, .40 cal and 9mm are two such cartridges that a .010" variance in seating depth could create a viable pressure effect. And more than .010" could effectively cause an excessive difference in pressures.

Speer described seating depth effect in the #10 by seating a 9mm to a tested depth and powder charge that was producing a safe and normal 28,000. When they increased the seating depth by .030" using the same powder charge, pressures spiked to a dangerous 63,000. So it's a combination of powder charge and seating depth, that determines what is safe, and how much variance allowance you have of either.

All the published powder data I've ever seen or used, is designated in .1 gr. increments. So I would gauge your charges in .1 gr. increments for the sake of eliminating any confusion from the process.

GS

RandyP
June 17, 2013, 07:37 AM
One of the factors affecting my decision to ONLY use Win 231/HP-38 is that there is generally a pretty liberal range of powder weight going from min to max and I opt to load mid range, giving myself a nice safety 'cushion'. It also meters very consistently in my Lee gear.

Blue68f100
June 17, 2013, 08:49 AM
I'm new to reloading and have been gathering the necessary equipment to start to reload .40 cal. ammo I'm at the point where I will soon be measuring my powder using the lee powder discs. Now when I weigh my charge on the scale and it reads something like 7.045 or 7.102 or whatever and it calls for just7.0 grains would the extra 10th or hundredth make a big deal? I know ideally 7.0 on the nose would be best because that is what it calls for but how accurate does it need to be and still be safe, I'm afraid if I am over just a bit I could harm myself or do I just need to worry about double charges? Thanks a bunch for all your help I am learning a lot on this forum with all the knowledge everyone has.

Since your have measurements in the 0.001 range are you in GRAMS and NOT GRAINS? There is a huge difference.

As for variations, a 0.1grains is acceptable. If your at the top end of the load I always make sure the deviation does not take me over max. Some powders like Unique which is a large corn flake can give you 0.2gr and greater swing. Another thing I look at is % of change the deviation gives you. If your loading a 380 and the charge is 4.0 gr a 0.1gr is a 20 % swing in your load. But on a 38 which takes over twice the powder < 10%. When you get to large capacity hand gun or rifle loads the small changes have little effect. But on small cases it has a big effect.

Load safely.

Walkalong
June 17, 2013, 09:15 AM
it reads something like 7.045 or 7.102 or whatever and it calls for just7.0 grains would the extra 10th or hundredth make a big deal?As long as 7.0 is not max, it is fine. Start low, work up, and take into consideration the range the measure is throwing. 6.9 to 7.1 or whatever.

jerkface11
June 17, 2013, 10:01 AM
The lee scale is not the most user friendly. You may want to upgrade to pretty much anything else.

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