Frequently Asked Questions
Click on a question to be taken to the answer
1.
What
are 0s, 1s, 2s, 3s, etc.?
2.
How do I prove
that sorting ammo by rimfire concentricity has a benefit in my rifle system?
3.
Can
a bullet by straightened that is out of round?
4.
How
do I setup my gauge? Where should the
indicator contact the bullet?
5.
How
and when should I clean the rollers or the indicator tip?
6.
Do
the bearings in my gauge need to be lubed?
Should I pull my gauge apart?
7.
Why
are some lots of ammo better than others?
8.
Do
I need to set the dial indicator to 0.000 when I setup my gauge?
9.
Why
did you shoot twenty round groups in your testing?
10. At
what measurement should I keep or cull bullets?
11. How
do I identify loose seated bullets?
12. How
accurate are loosely seated bullets?
13. Can
I reverse the drive arm on my machine?
What are 0s, 1s, 2s, 3s, etc.?
When we sort ammo we use the following
standards:
|
A bullet is considered a: |
If the run-out is between:
|
|
0 |
0.000 and 0.005 |
|
1 |
0.005 and 0.015 |
|
2 |
0.015 and 0.025 |
|
3 |
0.025 and 0.035 |
|
4 |
0.035 and 0.045 |
How do I prove that sorting ammo by rimfire concentricity has a benefit in my rifle system?
The
first thing you will need to do is sort some of your ammunition. You will want to sort enough ammunition so
that you have twenty 0s and twenty 3s.
Take two targets to the range, preferably on a calm day, and shoot the
0s on one target and the 3s on the other.
Score both targets and this should be more than enough to prove the
benefit of sorting ammo for your rifle system.
Testing
and benefits is also dependant on the distance you are shooting. The benefits in match grade guns at 50 yards
or meters is very apparent. At 100
yards or meters it is a very significant difference. At 200 yards or meters, it is the difference of night and day.
Can a bullet by straightened that is
out of round?
The
short answer is that we have never been able to make this work. You can make a bullet appear to be straight using
our gauge. Spin the bullet until the
high side is up as seen by the dial indicator.
Tap on the top of the indicator needle that is protruding from the top
of the gauge. This may take a couple of
iterations but eventually you will be spinning the bullet and it will appear to
have no run-out. We tried this and then
shot them to see if the results were the same as out of the box zeros. What we learned was that these straightened
bullets shot like their original run-out indicated. In other words if we started with threes and then straightened
them, they still produced a group like bullets with three thousandths run-out.
What
we theorize is happening is that we are straightening the part of the bullet
that is outside the case but not affecting the base of the bullet that is
crimped inside the case. Remember we
are using bullet run-out to actually give us an indication of the angle of the
base of the bullet. It is the angle of
the base of the bullet upon exiting the muzzle that is causing the dispersion that
we see at the target.
How do I setup my gauge? Where should the indicator contact the
bullet?
You
should have the indicator tip positioned one-fourth to half the way down the
ogive of the bullet. This should give a
very precise and sensitive reading. It
will also be a much smoother reading than indicating on the knurrled section of
the bullet. This is a good picture of
where the indicator tip should be positioned on the bullet.
How and when should I clean the
rollers or the indicator tip?
Yes
is it critical to keep the roller shafts and indicator tip clean while
sorting. Some bullets will have a
little lube all the way up on the case and this will transfer to the shafts.
These shafts will start to look "dull" when lube is on them. This needs to be cleaned off periodically
while sorting. I do it when I clean the
dial indicator tip. A cleaning patch with alcohol is more than sufficient
to wipe off any buildup. We are making
very precise measurements in a very precise machine. "Cleanliness is next to Godliness"
Do the bearings in my gauge need to
be lubed? Should I pull my gauge apart?
The
bearings in the gauge do not need to be lubed.
The shafts are press fit into the bearings and pulling the gauge apart
will most likely damage the end of the shafts.
Further the Olympic model gauge is hand tuned to have less than 0.0005
total machine error and pulling the gauge apart and reassembling it will more
than likely introduce more machine error, which will affect the accuracy of
ammo measurement. If you feel that you
have developed a rough feeling bearing, please contact us to evaluate the
best course of action.
Why are some lots of ammo better
than others?
Our
customers are definitely learning that some lots of ammunitions have a better
yield of bullet run-outs than others.
This means that some lots may have as many as 10 to 15 percent of the
bullets with zero run-out. Other lots
may have as low as 5 percent zeros.
Obviously what we want to buy is the ammo that has the highest
percentage of zero run-out bullets.
Several people have told me that what they now do is purchase a brick of
several different lot numbers. After
determining the yield of bullet run-outs and which velocity performs best in
their rifle system, they then purchase case size quantities of that lot number.
Do I need to set the dial indicator
to 0.000 when I setup my gauge?
No
you do not. We are only concerned with
how much the dial indicator needle moves, not that it starts at zero and moves
to three.
Why did you shoot twenty round
groups in your testing?
In
order to answer this question we first need to define a few terms:
RIFLE
SYSTEM: The combination of the rifle and the ammunition as it will be used in
competition.
AVERAGE
DISPERSION: A calculated value usually
based on averaging several five shot groups.
TOTAL
DISPERSION: The maximum group size that
the rifle system produces.
STANDARD
DEVIATION: The statistical measure of
spread or variability of the data.
The
goal of our research was to determine the total dispersion associated with
bullet concentricity in a rifle system.
Obviously several steps were taken in order to discover what this total
dispersion is. The testing was
performed at an indoor range to eliminate environmental (i.e. wind)
influences. A 2 inch ballistic test
barrel was used to minimize harmonics.
A machine rest was used to eliminate human error. Once all of these controllable factors are
addressed we can truly learn what the total dispersion of the rifle system
is. In order to find the total
dispersion of the rifle system we need to fire a sufficient number of rounds
into a group to prove that all of the bullets are landing within that group and
the group size is not getting any bigger.
The data we produced in 2004 at H-S Precision statistically supports our
conclusion. If you look at the group
sizes across 80 rounds (4 twenty round groups) for the premium ammo you find
that the data is very consistent with a low standard deviation. Therefore we have found what the total
dispersion of the rifle system is by using twenty round groups.
Unfortunately
what we encounter in publications about rimfire accuracy in the United States
is average dispersion. This number is
usually calculated by taking six 5 shot groups and averaging the group size
produced. A calculation such as this is
only valid if there is a high degree of consistency in the group sizes and a
very low standard deviation for the data.
An example of where calculating the average dispersion would be valid
would be if our six group sizes were 0.27, 0.29, 0.30, 0.28, 0.29,
0.28. This data would produce and
average dispersion of 0.285 plus or minus 0.010. The data is consistent and the standard deviation is small. Granted we still have not learned what the
total dispersion of the rifle system is but we do have a good indication of the
accuracy of the rifle system supported by consistent data.
Lets
work through a real world example. In a
recent accuracy related publication in the United States, the authors were
trying to determine the accuracy benefit of having a certain device attached to
a rifle. Six 5 shot groups were fired
with the device attached and the experiment was repeated without the device
attached. The data with the device
attached was: 0.480, 0.505, 0.505,
0.575, 0.400, 0.260. The data
without the device was: 0.745, 0.520, 0.540, 0.450, 0.345, 0.400. When we calculate the average group size for
each with the standard deviation it is: attached 0.454 plus or minus
0.111 no device 0.496 plus or minus
0.133. We can all see the obvious
conclusion that the groups with the device averaged 0.042 smaller. When we realize that the standard deviation
of the data was 3 times this number we know we havent produced any consistent
data though which we can make a genuine conclusion. Obviously we are not making the statement that this device does
not improve rimfire accuracy. We are
concluding that the data presented in this article does not statistically prove
the benefit of using this device.
At what measurement
should I keep or cull bullets?
Our
research discovered the following formula: for every 0.001 in bullet run-out,
group diameter increases 0.1 at 50 meters.
This question has no straight forward answer, because it depends
somewhat on the shooters abilities and expectations. However, we believe that almost everyone should cull bullets with
between 0.003 and 0.005 run-out because these could easily cost you
points. If you are a competitor going
to an Olympic Finals match, you probably only want to be shooting bullets with
0.000 run-out.
How do I identify loosely
seated bullets?
When
measuring a normal bullet in the machine, the indicator needle will swing
smoothly from a high to low reading.
When measuring a loose seated bullet you will see the dial indicator
needle jump back to a lower number.
Some loosely seated bullets appear to make the needle vibrate as it
swings. Quickly being able to identify loosely
seated bullets can only be learned with experience. These hints should get you started correctly.
How accurate are
loosely seated bullets?
Our
research provided proof that loosely seated bullets shoot nearly as well as
hard seated bullets with zero run-out.
The only plausible theory at this time is that loosely seated bullets
self center as they are chambered in the rifling of match grade guns. In simple terms the order of accuracy that
was proven in our research was 0.000 < loose seated < 0.001 < 0.002
< 0.003 < 0.004 . . . etc.
Can I reverse the drive
arm on my machine?
The Olympic Model is not
reversible. Never disassemble this
model. In the final assembly process,
run-out error is indexed, offset and then pressed together. This process eliminates error in the
machine. The new Club Model is made to
reverse the drive arm to either left or right hand, please see instructions.