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How much does 1/10 of a Grain matter?
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<Bill>
posted
Sometimes when I am reloading big cartridges, I might go a 1/10 grain over or under, do you think it makes much of a difference?
 
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In my experience, no, unless you are loading right on the edge of a maximum charge or you are reloading a cartridge where the spread between the low and high charges are very slim.

 
Posts: 598 | Location: Missouri | Registered: 16 June 2000Reply With Quote
<yorick>
posted
Eeek! I just try to keep the big ones within .5 gr of desired (ie max variation 1)

The way I figure it, if 90gr is the desired load, 90.5 - 89.5 gives a max percentage deviation of about 1%

If translated into velocity, (target velocity 3000 fps) max difference of around 33 fps.... I can live with that...

But I've never been much of a "attention to detail" kind of guy....

Smaller cases I pay a closer attention to, basically I try to use the 1% rule of thumb on all of them...

(ie: 1% of a 40 gr 243 is alot smaller gr variation than 1% of the 90 gr 338 )

[This message has been edited by yorick (edited 02-22-2001).]

 
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<AKI>
posted
Bill. Max load in the 25 ACP is around 1 grain so 1/10 grain is 10% and critical indeed for everything, especially safety. It�s the size that matters AKI
 
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Picture of Bob338
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Powder manufacturers generally accept the fact that up to 3% of a powder charge is unburned. It is the component least affecting accuracy in a cartridge. Dismantle factory ammo and weigh the charges. It will amaze you. Bob
 
Posts: 1261 | Location: Placerville, CA, US of A | Registered: 07 January 2001Reply With Quote
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Picture of Zero Drift
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Bill:

In big case cartridges, you should not see much velocity difference if any. If you are really concerned, simply use a chronograph. Actually, you should spend a lot of time behind a chronograph if you are a reloader. A chrono can tell you everything you need to know about your reloading accuracy.

Z

 
Posts: 10780 | Location: Test Tube | Registered: 27 February 2001Reply With Quote
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It depends upon what you mean. If you are concerned about the bullet strike, I believe Sierra did some tests which indicated that a difference of a full grain would not change the bullet strike more than .25 inches at 100 yds.

If we are talking about pressures and you are right at max and the temperature is up on your next trip to the range, you might break something.

Trying to milk the last little bit out of a load is silly. Go to the magnum version! Ku-dude

 
Posts: 959 | Registered: 27 February 2001Reply With Quote
<Frank>
posted
I notice at bench rest and 1000yrd shoots most guys just use a high end powder measurer.As a matter of fact some of the benchrest guys only know how many clicks on the measurer not sure on the weight. So I think that a 1/10 or so does not make a noticeable difference.
 
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<holtz>
posted
I have never found 1/10th of a gr., or even 1/2 gr., to make a difference. But, in one of my favorite .338 Win. loads, one gr. opens groups from sub 1" to about 2.5" while adding only 10 fps. Go figure.

Steve

 
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<PowderBurns>
posted
Depends on the capacity of the case.

That said, a 1% variation in charge will NOT yield a 1% variation in pressure/velocity. The pressure/velocity curve is not a straight line.

0.10 gr. is a minimal variation. It's nice to get things right on the money, but accuracy comes from case prep, not charge volume.

As for MAX pressures. Max load data provides a safety margin of about 5X to compensate for variables in charge, primer, case, chamber necking, etc. Of course it's possible to get pressure indicators before reaching the max load, but 0.10 gr. is not going to make or break an otherwise safe load combination.

Yeah, factory ammo is all over the place. Variations in seating depth, bullet length, neck tension, case length. --Unless you're springing for the "match grade" ammo at a buck a shot or more.

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www.hotboards.com/plus/plus.mirage?who=powderburns

 
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<Rust>
posted
Unless you are benchresting and have gone all the way with brass prep, bullet sorting and everything else first, .1 gr in a rifle cartridge with a capacity around that of a .223 or larger is of no practical consequence.

In a large case, when you are dumping over 100 gr of powder, it isn't even worth considering .1 gr.

 
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<JoeM>
posted
Hello,
There are some powders that will not run through a (standard grade) measure with .1 grain accuracy. Some of these powders have to be hand-weighed if you want accuracy that critical. .1 grain will not make one whit of difference in most rifle stuff. For extra small cap cases, yes, for benchrest, yes or maybe, for everything else, probably not.

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Load Hot, Shoot Straight
JoeM

 
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<David E>
posted
Also remember that most powder is hydroscopic (amsorbs moisture) so some extent. This is why the benchresters think that a very consistant VOLUME is more important than a very consisant WEIGHT. Weight can vary due to moisture content, while volume doesn't.
 
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Picture of 500nitro
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For high capacity cases that 1/10 is absolutely negligible.On a small case using less than a 3 or 4 grain charge it is noticeable.
My Bianchi (38spl 148gr dewc) loads are susceptible to tenths, but my 30-06 feels nothing.
I generally only weigh every tenth charge to check, but once I have set the powder thrower I tend to run with set volume rather than weight.
 
Posts: 1069 | Location: Durban,KZN, South Africa | Registered: 16 January 2001Reply With Quote
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I agree I never weigh charges. I just set up the measure and load, checking it occasionally. If a powder won't shoot thrown charges I move on to another powder. I don't have limitless time to load ammo. The factory does not weigh charges even in the most expensive match ammo. This should tell us something.
 
Posts: 813 | Location: Left Coast | Registered: 02 November 2000Reply With Quote
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