[RELOADING] how consistent should a powder measure be/
J. Spencer
measure which came as part of the Lyman Expert kit. Oh, I can't
remember the model number, but it consist of an upright clear plastic
hopper to hold the powder, and an adjustable cylinder into which the
powder falls before being desponsed into the case below. It also has a
little hammer on it - you know the sort of measure I mean, I'm sure :-)
I use two powders: Reloder 12 (RL-12) for the 70 grain bullets, and
Hodgson's H4350 for the 100 grains. (Why these powders? Because there
isn't much choice here.) The Rl-12 is extruded and the granules have a
length to diameter ratio of something approaching 1. The H4350 is also
extruded but its length to diameter ratio is probably nearer 3:1 of
4:1. The RL-12 trickles quite nicely, seldom do I feel the cyclinder
cutting the granules as it is turned. The H4350 isn't so clever,
turning the handle of the cyclinder normally involves crunching some
granules. (Digression: is there *any* risk of fire from the friction?)
I get more consistent charges with RL-12 than with H4350. (I'm using
just the big slide to minimise the number of granules that get
trapped.) Here are some values obtained three ways: 1) measure every
charge as it is thrown (first series both powders); 2) measure every
tenth charge after loading a batch (second & third series RL-12); 3)
measure every charge after loading a batch (second series H4350). I
didn't do it this way because it was scientific or anything, it was just
the way I did it because I wasn't happy with the H4350. The results:
RL-12 H4350
37.4 44.0
37.4 43.3
37.6 43.3
37.6 44.0
37.4 43.8
37.5 43.3
37.5 43.5
37.5 43.5
37.5 43.5
37.5 43.5
37.4 43.5
37.3
37.7 43.5
37.4 43.2
37.4 43.3
43.6
43.7
37.4 43.6
37.4 44.0
37.4 43.9
37.4 43.8
37.1 43.9
37.4 43.5
43.5
37.5 43.7
37.5 43.5
37.1
37.4
37.5
I haven't done any stats on the results, but it looks to me like the
H4350 is much less consistent than the smaller grained RL-12. Might
this help explain why the 70 grain SP flat tailed bullets are more
accurate (consistent) than the 100 grain BTSP bullets. (The bullets are
Hornady.) Is the problem of consistent charge common? It it the powder,
the measure? When someone says "I increased the charge by 0.2 grain" is
that a *mean* increase of a precise increase? Suggestion/comments
welcome.
-- Jonathan
Mail : Computing Lab., University of Newcastle-upon-Tyne, NE1 7RU, England
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Emmanuel Baechler
# Just how consistent should a powder measure be?
IMHO, the right tolerance is +- 0.1 grain. This ensures regularity of loads
(and thus accuracy) and safety (for loads near the maximum level).
This require a measurement (with the needed adjustments) AT LEAST
every ten loads. A measurement every 5 load is even better.
If you really want to build match grade ammo, individual measurement
cannot be avoided.
Emmanuel Baechler. | Tel.: ++41-21-693-2732
Laboratoire d'Intelligence Artificielle | e-mail: baec...@lia.di.epfl.ch
Ecole Polytechnique Federale de Lausanne | or: baec...@liasun6.epfl.ch
MA-Ecublens | Standard Disclaimer
CH-1015 Lausanne Switzerland
Ban the bomb. Save the world for conventional warfare.
Toby Bradshaw
#If you really want to build match grade ammo, individual measurement
#cannot be avoided.
I beg to differ. It's rare to even see a powder scale at a big
benchrest match. Most competitors don't even know what the charge
weighs (despite the equipment list), they're thrown from a Culver
or Jones measure. Admittedly, most powders used in BR are easy
to meter, but the fact remains that the vast majority of shooters
in the most accuracy-demanding shooting sport never weigh a charge.
-Toby Bradshaw
to...@u.washington.edu
Bart Bobbitt
: Admittedly, most powders used in BR are easy
: to meter, but the fact remains that the vast majority of shooters
: in the most accuracy-demanding shooting sport never weigh a charge.
But the top shooters in the `other most accuracy-demanding shooting sport'
do weigh powder charges to +/- one tenth of a grain. This is highpower
competition where a 20 fps velocity spread means 8 inches (eight tenths MOA)
vertical stringing at 1000 yards using a .308 Win. That same velocity
spread will string only about 0.3 inches (one tenth MOA) at 300 yards
in typical .22 and .24 caliber benchrest cartridges.
Weighing powder charges only becomes critical when ranges greater than
300 yards are encountered and accuracy is the name of the game. If the
benchresters needed to weigh powder charges, they would. They don't so
they won't.
BB
Toby Bradshaw
#Toby Bradshaw (to...@stein.u.washington.edu) wrote:
#
#: Admittedly, most powders used in BR are easy
#: to meter, but the fact remains that the vast majority of shooters
#: in the most accuracy-demanding shooting sport never weigh a charge.
#
#But the top shooters in the `other most accuracy-demanding shooting sport'
#do weigh powder charges to +/- one tenth of a grain. This is highpower
#competition where a 20 fps velocity spread means 8 inches (eight tenths MOA)
#vertical stringing at 1000 yards using a .308 Win. That same velocity
#spread will string only about 0.3 inches (one tenth MOA) at 300 yards
#in typical .22 and .24 caliber benchrest cartridges.
In my testing, 0.1gr is worth about 10fps in a 6PPC. I chronographed
some test loads last weekend, thrown from a measure, and the two loads
I had were 3226 and 3254fps, each had an SD of 9fps. I'd be surprised
if even half the SD is due to variation in powder charge, probably
half of it is the primer alone. These were my best loads with two
different bullets, and the final test groups were 0.535" and 0.539"
at 300 yards. In good conditions, I couldn't afford 0.3 of vertical
from the powder charge variation, and I don't get even 1 bullet of
vertical at 300 with a good load, all charges thrown from a measure.
#Weighing powder charges only becomes critical when ranges greater than
#300 yards are encountered and accuracy is the name of the game. If the
#benchresters needed to weigh powder charges, they would. They don't so
#they won't.
If the measure could only hold +/- a tenth, you would have 20fps extreme
spread just from powder charge, giving ~0.2" of vertical at 200 yards just
from the powder. In good conditions, it's just about impossible to win
with that much vertical in a 200 yard target. So, I'd argue that even
such small variations _do_ matter in benchrest, even at ranges under 300
yards. Weighing the charges won't help, though, because the powder
measures can already throw to 0.1 grain or better. Take a look at the
inside of a Jones measure, and how it cuts the powder grain. One of our
local shooters is a fan of 4198, which is relatively long and skinny. He
has no problem holding a tenth with a Jones measure. Most any measure
will hold a tenth with H322, which is probably the most widely used
powder in BR these days.
-Toby Bradshaw
to...@u.washington.edu
Bart Bobbitt
: In my testing, 0.1gr is worth about 10fps in a 6PPC. I chronographed
: some test loads last weekend, thrown from a measure, and the two loads
: I had were 3226 and 3254fps, each had an SD of 9fps. I'd be surprised
: if even half the SD is due to variation in powder charge, probably
: half of it is the primer alone. These were my best loads with two
: different bullets, and the final test groups were 0.535" and 0.539"
: at 300 yards. In good conditions, I couldn't afford 0.3 of vertical
: from the powder charge variation, and I don't get even 1 bullet of
: vertical at 300 with a good load, all charges thrown from a measure.
Sounds about right to me. I think a 9 fps SD is about a 30 fps spread.
And them pesky primers are indeed half of the velocity spread you get.
I wish Federal and Remington would make more uniform primers; like the
RWS ones from Germany.
I should have said a 1-tenth spread, not +/- a tenth. And those powders
and measures favored by the BR folks are indeed well suited to chucking
charges at the range.
BB
J. Spencer
#In article <C9t81...@fc.hp.com> ba...@hpfcla.fc.hp.com (Bart Bobbitt) writes:
##Toby Bradshaw (to...@stein.u.washington.edu) wrote:
[munchy munchy]
# Weighing the charges won't help, though, because the powder
#measures can already throw to 0.1 grain or better. Take a look at the
#inside of a Jones measure, and how it cuts the powder grain. One of our
#local shooters is a fan of 4198, which is relatively long and skinny. He
#has no problem holding a tenth with a Jones measure. Most any measure
#will hold a tenth with H322, which is probably the most widely used
#powder in BR these days.
So where am I going wrong? You've seen that the charges thrown by my
measure vary by up to .9 grain overall. I always knowk the hammer two
strokes when the lever is up, and one more stroke after the cartrdige
is charged; I refill the hopper as soon as the powder level has dropped
by about a quarter off full. Is it that the Lyman measure is crap, or
something I'm overlooking? Weighing every charge would be a real
pain...
Someone else meantioned a powder trickler, what is it?
Bart Bobbitt
hollow point match bullet:
Drop In Inches at Ranges
Muzzle (Difference from 3235 fps)
Velocity 100 yd. 200 yd. 300 yd.
--------- ------- ------- -------
3245 fps 1.74 7.71 19.19
(+0.01) (+0.05) (+0.13)
3235 fps 1.75 7.76 19.32
3225 fps 1.76 7.81 19.44
(-0.01) (-0.05) (-0.12)
My earlier posted vertical spread data for a 20 fps velocity spread with
like bullets was too big. This data shows the spread to be:
* 0.02-in. at 100 yards.
* 0.10-in. at 200 yards.
* 0.25-in. at 300 yards.
Toby Bradshaw was right on the money in stating that benchresters frown
when a 0.2-in. spread at 200 yards (or a 0.3-in. spread at 300 yards) is
produced. Statistically, about 70% of the groups fired will be only
be strung vertically only 70% as much as the table shows. That means
most groups will be strung vertically about:
* 0.014-in. at 100 yards.
* 0.070-in. at 200 yards.
* 0.175-in. at 300 yards.
Keep in mind that bullet unbalance will add some to these numbers. Those
bullets who travel downrange very well stablized (very little nutation or
gyration) will deflect less than the less stablized ones (more nutation
or gyration). Dr. F.W. Mann documented some excellent tests in his book
"The Bullet's Flight from Muzzle to Target," first printed in 1907 and
recently reprinted. These tests showed how both well balanced and less
balanced bullets compare in the distance they move at right angles to
their downrange path.
Toby's comment that one needs this level of vertical accuracy to do well
in benchrest matches is absolutely correct. I didn't quite believe or
understand this until I crunched the numbers. Shame on me for making
assumptions without first checkin' out the facts.
And his comment about primers causing about half that variance is also
very correct. Primers, in my opinion, cause about 70% of the velocity
spread. Powders are quite uniform in their performance.
A friend who has an Oheler System 43 (the one that measures groups, fps,
pressure, plots curves, etc.) is gonna do some extensive tests this fall.
His plans are to test several brands of cases, primers and powders with
Sierra's 155-gr. Palma bullet in the .308 Win. case. We feel there is
strong evidence that a milder, gentler and slower start of the bullet into
the rifling produces smaller groups at any range. When I've got and
compiled the test data, I'll post it in this group.
One can look at ballistic tables and find out what vertical dispersion
can be caused by velocity spread. If the velocity steps are 100 fps
apart, just take 20% of the drop difference shown for a 20 fps velocity
spread. When you check these numbers at ranges beyond 500 yards, it's
evident that keeping velocity spread as low as possible will improve
ones chances of shooting small groups at long range.
BB
Henry E. Schaffer
Here is a slightly updated review of what is generally
considered to be a high quality mass-produced powder measure.
There are semi-custom ones which are supposed to be better.
My Lee Auto-Disk Deluxe powder measure works like a charm for
my .38 Spl reloading, giving me just about 3.8 gr. of Bullseye
with monotonous regularity. I still weigh every 25th charge
on my Hornady balance, but all that does is tell me where in the
3.7 - 3.8 gr. interval that charge falls. Still, this measure
doesn't meet all my needs, particularly it is not continuously
adjustable. It uses holes in the disk to meter the powder, and
so one only gets amounts which those holes deliver, and they
don't get up high enough for large rifle loads. (There is a two
disk set, called the Micro-disk or something, which gives finer
adjustment by stacking two disks to combine two different sized
holes, but it looked like too much trouble for me.)
I decided that I *needed* a powder measure with a micrometer
adjustment, and one which would be very repeatable and very
flexible. After quite some investigation I settled on a Redding
Product, the Model #3 Match Grade Powder Measure. I bought it
from Sinclair. (I have a lot of respect for Sinclair's judgement,
and the fact that they carried it added to my comfort level.)
I got it with their "Universal" micrometer insert. This is a
micrometer barrel, with an end which fits into the cavity in the
rotor, and depending on the micrometer setting the end allows
more or less volume in the cavity. It is very easily set, and
very repeatable. The measure comes with a chart which gives
approximate weights for different settings for a dozen powders,
but it only takes a minute extra for a powder not on the chart.
I've been using this for rifle reloading, and it works well. I
use a lot of IMR 4895 and the powder grains are little sticks
and some of them get sheared each time the measure is worked. This
gives a little jerkiness, but is no real trouble. When loading
39.5 grains, the amount weighs out to this plus or minus .1 gr.
while I would prefer just a bit tighter measuring (I would prefer
plus or minus .05 gr.) this variation doesn't seem to worry bench
rest shooters. I suspect that I would get tighter measuring if I
used a powder which metered better than 4895.
Also Paul Perez wrote to me about his experience with another
Redding model. He polished the inside (cone shaped interior) of
the casting with a Dremel tool and got a noticeably improvement in
repeatability. I just took my #3BR apart and found that the
same place is really quite rough - pebbly. I polished it for a
while with a Cratex fine abrasive point in a Dremel, and then went
over with an extra fine. I didn't remove all the pebbly surface,
but I very noticeably smoothed it out and polished the surface.
I haven't used again for 4895, but I did use it to load 27 rounds
with 17.5 gr. of AA 2015 BR and weighed all of these charges.
11 weighed the right amount, 9 were within +- .025 gr. and 7 were
within +- .05 gr. for a total range of no more than .1 gr. (My
deviations are a quarter and a half of a tenth of a grain,
respectively, and were estimated by eye.) I haven't checked it
again using 4895.
I did set it up a bit differently than shown in the Redding
catalog. They show the baffle with the bent angle pointing upwards,
and the baffle perhaps 1/3 of the way from the bottom to the top.
Sinclair recommended that I set it with the angle pointing downwards,
and right at the bottom of the powder reservoir, with the bottom
of the angle trapped in place by the ends of the set screws which
keep the plastic powder reservoir in place.
Since I wanted to be able to use this powder measure for smaller
powder loads, I later ordered the (interchangeable) micrometer insert
for pistol loads. This is the same kind of micrometer body, but with
a solid body and only about the center 1/3 of it moving in/out to
change volume - so in effect it makes the cavity much smaller in
diameter, and so allows setting its volume more easily. I had to
load some cartridges with 2.1 gr. of Bullseye, and so I used this as
a test. I fiddled around to get the setting I wanted (the chart gave
settings for 9 powders, and said to set it at a reading of 17 to get 2.1
gr. - it was a bit light and I ended up with a setting of 17.5.) Then I
filled 40 cases and weighed every one on my balance. Most of the
weights were just at or a hair above 2.1 gr., with the highest one
being about .03 gr. too high and the lowest being about .03 gr. too low.
(That's about a third of a tenth of a grain, estimated by eyeing the
balance - which is marked in tenth grain graduations.)
The rotor works more smoothly with Bullseye than it did with 4895,
and that may have helped.
I'm very happy with this powder measure.
There is a set screw on the handle side of the rotor. This set
screw must be unscrewed in order to change the insert between the
rifle and the pistol versions. While I normally turn it finger
tight (using an Allen wrench) I forgot to do so recently, and left it
turned nearly all the way in but not to the point of requiring any
torque. What happened was that the powder measure (in the pistol
configuration) became much more consistent! I couldn't believe it,
so I tried snugging it down and then backing it off - and sure
enough that seems to be the problem. In the pistol range it now is
very consistent. I'll have to do some tests and get actual
numbers and also try this for the rifle insert.
--henry schaffer