Is there a way to measure rifling twist?
freshwa...@yahoo.com
pistols and rifles, and I don't know what the twist is on any of them.
It's one of the data points I try to keep on each piece I own.
I tried messing around with a tight patch and a cleaning rod, but it
was pretty bad; hard to get repeatable results. Not quite enough brain
cells to come up with anything more imaginative. Looking down the
barrel definitely doesn't work! <grin> All ideas much appreciated.
PS: Have I got this right: as I look down the barrel from the breech
toward the muzzle, if the bullet would spin clockwise, that's a
right-hand twist, correct? And yes, I am one of those people who can't
tell right from left!
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Louis Boyd
# Is there a good way to measure twist? I recently acquired several
# pistols and rifles, and I don't know what the twist is on any of them.
# It's one of the data points I try to keep on each piece I own.
#
# I tried messing around with a tight patch and a cleaning rod, but it
# was pretty bad; hard to get repeatable results. Not quite enough brain
# cells to come up with anything more imaginative. Looking down the
# barrel definitely doesn't work! <grin> All ideas much appreciated.
#
# PS: Have I got this right: as I look down the barrel from the breech
# toward the muzzle, if the bullet would spin clockwise, that's a
# right-hand twist, correct? And yes, I am one of those people who can't
# tell right from left!
#
For a quick check, than a tight patch I use a bronze brush with a ball
bearing handled cleaning rod. From my experience it tracks better than a
patch which can slip on a round jag, and with with less effort. I make
the measuremet by pulling or pushing the brush so that it tends to
tighten the threads between the brush and the rod depending on the
barrel twist direction. I put a piece of tape on the rod folded to
stick off the side and measure the distance to achieve 1 turn using a
tape measure relative to some fixed point on the barrel or action. I'd
say the accuracy is within 1/4" for typical barrels. On pistols you'll
usually have to work with a reduced angle of rotation, so a protractor
is handy for measuring the angle of rotation.
A more accurate but complex method is to use a borescope. I wouldn't
spend the money on a borescope just to measure twist rate, but it's a
very useful tool for checking erosion and other forms of bore damage.
When I want the best accuracy I clamp the barrel to the bed of my
milling machine and clamp the borescope to the quill. I put a bushing
over the borescope tube to keep it centered. The mill's digital readout
can measure to .0005" but it's difficult to tell where the edge of a
given groove is located with the shallow tangent angle to better than
about 0.01". On a six groove barrel there are twelve edges which can be
measured and averaged. At that resolution it's not unusual for the
twist rate to be measurably non-uniform over the length of the barrel.
Arguably the muzzle end is most important for bullet stability.
calculations. For accurate measurements the bore scope needs a reticle.
Mine is equipped with a video camera which can provides a similar
function. I've only done this on a few barrels to check the twist rate
uniformity.
You are correct in your description of a right hand twist. It's the
same as a standard right hand thread machine screws if you consider the
barrel to be like a long nut and the bullet a short bolt. The bolt or
bullet must turn clockwise (as you view it) to moves away from you.
Bolts and nuts are usually specified in turns per inch while barrels are
specified in inches per turn.
J. Nielsen
#Is there a good way to measure twist? I recently acquired several
#pistols and rifles, and I don't know what the twist is on any of them.
#It's one of the data points I try to keep on each piece I own.
#
#I tried messing around with a tight patch and a cleaning rod, but it
#was pretty bad; hard to get repeatable results. Not quite enough brain
#cells to come up with anything more imaginative. Looking down the
#barrel definitely doesn't work! <grin> All ideas much appreciated.
I often use a tight-fitting wood or plastic dowel, about 1/2" long,
fitted/glued to the threaded end of the spoke from a bicycle wheel. Putting a
sharp ninety degree bend on the other end of the spoke makes it easy to tell
the turning of the dowel.
#PS: Have I got this right: as I look down the barrel from the breech
#toward the muzzle, if the bullet would spin clockwise, that's a
#right-hand twist, correct?
Correct. In fact, it doesn't matter whether you look from the brech or
muzzle end.
--
-JN-
Greg Mortensen
#Is there a good way to measure twist? I recently acquired several
#pistols and rifles, and I don't know what the twist is on any of them.
#It's one of the data points I try to keep on each piece I own.
Try Cerrosafe from Brownells[1]. You can find the instructions here[2].
Regards,
Greg
[1] http://www.brownells.com/aspx/NS/store/productdetail.aspx?p=384&s=
[2] http://www.brownells.com/aspx/NS/General/DisplayPDF.aspx?f=Inst-446.pdf
--
\|/ ___ \|/ thev...@pobox.com +----- 2048R/38BD6CAB -----+
@~./'O o`\.~@ | 02BD EF81 91B3 1B33 64C2 |
/__( \___/ )__\ | 3247 6722 7006 38BD 6CAB |
`\__`U_/' +--------------------------+
Ragnar
# Is there a good way to measure twist? I recently acquired several
# pistols and rifles, and I don't know what the twist is on any of them.
# It's one of the data points I try to keep on each piece I own.
#
# I tried messing around with a tight patch and a cleaning rod, but it
# was pretty bad; hard to get repeatable results. Not quite enough brain
# cells to come up with anything more imaginative. Looking down the
# barrel definitely doesn't work! <grin> All ideas much appreciated.
#
# PS: Have I got this right: as I look down the barrel from the breech
# toward the muzzle, if the bullet would spin clockwise, that's a
# right-hand twist, correct? And yes, I am one of those people who can't
# tell right from left!
Seems to me that it would be lots easier to contact the company that
made them (many of them have something called a website) and ask for the
info.
sta...@prolynx.com
lot of manufacturers' catalogs will give the twist in their barrels for
their guns, if you just gotta know. I can see it being a problem with
something like a .223 where there's been a number of different twists
in use and you need to know what it is to get the right bullet weight.
The barrels are long enough that you can get good enough results with
the patch on the cleaning rod or a brass brush, use a flag of making
tape on the cleaning rod and count the turns vs. length of rod.
For most anything else, stick to published loads for the caliber and
you won't have any problems due to rifling twist. Not really one of
those things that critical to know these days for most guns.
Stan
freshwa...@yahoo.com
or muzzle end."
If I"m looking from the breech end on a right-hand twist barrel, I see
the bullet turning clockwise. If I look down the barrel from the muzzle
end, I see the bullet turning counter-clockwise. Enough synapses have
to fire in coordination for me to realize that both of those
observations are of a right-hand twist. This is quite unlikely in my
case! Actually, it's not too bad if I let my hands do the talking. It's
when the silly verbal cortices get involved that trouble starts. But
isn't that always the case--open mouth, insert foot?
freshwa...@yahoo.com
a computer all day long, the last thing I want to do is hack on a
computer some more when I would really rather be enjoying my guns.
Ragnar wrote:
> ...
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freshwa...@yahoo.com
on the cold, cold, cold winter days.
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