Correct headspace is essential to accuracy, reliable functioning, and good case
life. Here is how you measure it, make corrections, and also measure throat
Headspace is a very simple concept that is both easy to understand and easy to
measure, especially in any break open gun like the TC Encore or Contender/G2.
I'll show you how.
Too many barrels are given up on as unsatisfactory, or, worse,
folks leave the TC system in despair simply because of headspace issues. Don't
be one of them! The methods you get away with shooting bolt actions simply do
not work with springy break open actions. The break open actions are different
and must be handled differently.
Understanding headspace can literally save you hundreds of dollars,
thousands of dollars if you are one who does a lot of barrel swapping in your
quest for accuracy and the performance dreams are made of.
This is what it should be. .001" BETWEEN THE CASE
HEAD AND THE BREECH FACE
Drawing courtesy of Alan Thompson. Thanks,
Note that the case shoulder is in contact with the chamber shoulder while
there is space between the case rim and the bottom of the rim counterbore,
indicating the case is "headspaced" or its forward movement stopped by the
shoulder, not the rim, and that the actual space at the head, "headspace,"
is .001" less than whatever the barrel-to-frame gap actually measures.
Diagrams in loading manuals don't seem to really
help get the concept across.
Most gun writers themselves don't seem to
If the factory understands anything other than
SAAMI headspace gauges, it does not show, nor are they helping you understand
and work with it.
The "local authority" who has double slammed the
barrel shut for nearly 40 years certainly is no help, nor is the guy who has
worked mostly with fixed barrel bolt actions going to be any help.
And some of the worst offenders putting out erroneous information are some of
the custom barrel makers. These are usually the ones leaning on headspace gauges
You cannot count on magazines, reloading manuals, the TC factory, the local
"authority" who has "reloaded for 40 years," or even most of the dealers and TC
aftermarket custom shops.
In fact, when it comes to the TC and NEF Handi-Rifle type break open guns, the
best thing to do with headspace gauges is toss'em in the trash.
They are meaningless, and misleading at best. A
"gauge" means nothing to you at all when you can take the measurements yourself
and KNOW exactly what the headspace is.
So don't go waste money on gauges. You don't need
them, and you don't want them. After you have worked with our Headspace
Indicator you will understand why.
Whether you shoot factory ammo or reload makes no difference. You still must
KNOW what the headspace is in any given barrel and frame combination.
You will be able to identify excess headspace
with either factory ammo or your reloads. If the headspace is excess with
factory ammo, anything over .006," you have grounds to exact a remedy from the
manufacturer of the barrel or the ammo manufacturer or both.
Excess headspace is the cause of many misfire
situations and erratic ignition which produces poor accuracy.
No headspace, meaning the case head is hitting on he breech-face when you close
the barrel, can cause the barrel to not close all the way. This has been a major
cause of misfires with Contenders since the first day they were produced. Or,
with Encores and G2s, it prevents the hammer from cocking when the barrel is not
closed all the way.
The issue of headspace is simply about making sure ammo fits the gun.
This should not be a strange concept. However,
believe it or not, ammo that fits right is more likely to work right. Imagine
What IS headspace?
The term is tossed around loosely all the time
and presumed to be something you have to use a "headspace GAUGE" to measure,
which is not only far from the situation, but also grossly misleading.
"HEAD," as in cartridge case HEAD, "SPACE," as in the space behind the head,
or the distance from the case head to the breech-face.
In the TC guns, it is the distance from the case
head to the firing pin bushing in the breech-face which actually protrudes out
from the frame a few thousandths.
This is what headspace is, and it is very easily
observed and very easily measured.
What Headspace is NOT!
Headspace is NOT the distance from the end of the
barrel to the breech-face, as is so often thought.
The distance from the end of the barrel to the
breech-face has NO bearing whatsoever on headspace, and this gap, referred to as
the barrel-to-frame gap, also has absolutely NO bearing on the quality or
function of the barrel. And contrary to statements by at least one purveyor of
custom barrels, there is NO optimum gap for accuracy. It can be a little, or it
can be a lot, as much as 1/8" and still have absolutely no bearing on accuracy.
While to some
it may be more esthetically pleasing to not be able to see daylight between the
closed barrel and breech-face, the amount of the gap has no bearing whatsoever
on the quality of the barrel, the function of the barrel, or the headspace.
In fact, there SHOULD be some gap between the end
of the barrel and the firing pin bushing. If the barrel hits too hard on the
firing pin bushing, it can do two things:
1) It can prevent the barrel from dropping into the frame far
enough to allow the barrel to close all the way and thus prevent it from firing,
2) we are finding it can often cause severe vertical stringing
of shots that ruins accuracy.
Both the barrel not closing all the way and
vertical stringing related to the barrel hitting on the firing pin bushing can
be corrected by either
1) facing material off the end of the barrel via filing, lathe
turning, or milling, or;
2) Removing the firing pin bushing and stoning a few
thousandths from the back side of the bushing, thus moving it back away from the
end of the barrel and giving some clearance between the two, i.e., creating some
To set up a barrel and frame combination so that
there is no gap or minimal gap can be a gross mistake, one discovered when the
barrel is later installed on a frame whose hinge pin hole is somewhat closer to
the breech-face than the frame the barrel was set up on.
HINGE PIN HOLE LOCATIONS DO VARY FROM FRAME TO
FRAME. I have only found about a .003" variance from frame to frame, but once
again, a barrel that hits on the firing pin bushing on one frame may not close
on the next frame if the hole in that frame positions the barrel closer to the
firing pin bushing.
Background behind the Bellm
The Bellm Headspace Indicator was developed as a
result of my many years of measuring case head protrusion from the ends of
barrels to determine the proper depth to ream chambers and is THE EASY WAY for
the average reloader and real pro alike to quickly and accurately determine
EXACTLY what the headspace is with his resized cases, rimfire ammo, and with
factory ammo as well, of course!
Most of the time I use a depth micrometer in the
shop for measuring how far a case or headspace gauge protrudes from the chamber,
but after all these years a depth mike is still rather touchy to get an accurate
measurement with while balancing it over the end of a case head and being very
careful to sense when the quill of the mike actually contacts the end of the
barrel. Getting lazy, or smarter in my old age, I started using a dial indicator
set up on the cross feed of the lathe to measure how far the case heads stuck
out. But few people have a lathe handy for doing this.
For about a year I toyed with the idea of making
this task simple and accurate for the amateur and real guru like. I think I have
"bingoed," and once you try it, I think you will wonder how on earth you ever
managed with the old ill-informed methods we all used for years. You will also
find that there is a "sweet spot" where the case head is neither too far from
the breech face of the frame or jammed forward by the breech face when the
barrel is snapped shut. This "sweet spot" is where mysterious Contender misfires
disappear, failure to cock with Encores and G2s disappears, case life improves,
and where the gun shoots its best. It will also prevent many extraction problems
that result from cases improperly sized being crammed into the chamber and then
not readily extract.
The bottom line is that chambers and throats have to be cut to a certain depth.
But it is YOUR responsibility to make sure your ammo fits the chamber.
what to do and being able to take the measurements tells you exactly what you
have so you can get it right.
The Bellm Headspace Indicator lets you take the same
measurements I have to take.
are needed! No comparators, no modified cases, no Stoney Point type equipment is
Put them away
if you have them, and if you don't have them, save your money, along with a lot
of frustration. With the Bellm Headspace Indicator you also measure the distance
from the ends of the rifling to the breech-face, the firing pin bushing.
Using the barrel itself as the only TRUE gauge
for the ammo and frame you are working with, you use the Bellm Headspace
Indicator to also measure bullet seating depth. Starting with a bullet seated
out a bit far, you measure how far the loaded round sticks out of the chamber.
The barrel IS your gauge. You do not need any other gauging device or gimmick to
do this. Nor do you have to buy anything else to go from one chamber to the
next. You don't even need a caliper or micrometer, and there is no error to be
made transferring information from one tool to another. You simply and
accurately measure what occurs in YOUR chamber.
Made for both Encore and Contender/G2 barrels.
The Bellm Headspace Indicator base is made double
ended, with one end at .810" for Contenders and the other at 1" for Encores. To
go from Contender to Encore mode, just loosen the set screw in the side of the
base and insert the dial indicator's stem from the opposite end.
Matching up the diameter of the appropriate end
of the indicator base with the breech end of the barrel positions the quill of
the indicator over the solid head of a case in the chamber, just outside of a
large rifle primer pocket.
You hold the
indicator base on the end of the barrel with your finger and thumb gripping the
base and barrel together. This keeps the base centered over the end of the
barrel while the offset indicator quill contacts the head of the case, missing
both small and large primer pockets. It is set up to work this way with any
cartridge from .22 Hornet up through the belted magnums and .404 Jeffery type
It is also used with rimfire barrels, but the
base must be moved over slightly to position the indicator quill over the head
of the case.
The ends of the base are recessed .1" so that
when positioned on the end of the barrel with a case in the chamber, the case
can project out of the barrel while the base itself is sitting flat on the end
of the barrel.
(Note: Early production bases were recessed only
.050," but to make it easier measuring throat length, we went to .1".)
Let's start. First measure the
Using a common set of feeler gauges you first determine what the gap is between
your barrel and frame's breech-face by closing the barrel on successively
thicker blades placed in front of the plug in the breech-face until you find the
blade that is gripped by the closed barrel. The thickness of the thinner blade
just below the one that is
tight in the gap is the gap's measurement you use. Make note of this amount.
If you use the barrel on more than one frame, you
should make a note of the serial number of that frame since the barrel-to-frame
gap will vary some from one barrel to the next.
scribe or stamp the barrel-to-frame gap on the bottom of the barrel lug for
reference later when switching from frame to frame or as a means of monitoring a
frame for signs of stretching. An increasing barrel-to-frame gap is an
indication metal is moving, meaning the frame is stretching.
The barrel-to-frame gap measurement must be taken
at a point directly above the chamber, between the firing pin bushing and the
end of the barrel. Because the firing pin bushing sticks out of the frame a few
thousandths, you cannot slide the blade in. You must close the barrel on the
The thinnest blade in most feeler gauge sets is
.0015," while some go to .001." If the barrel closes on the thinnest blade, call
the gap Zero.
To use the Bellm Headspace Indicator itself,
first loosen the knurled
knob at either 10 o'clock or 2 o'clock. This knob locks the dial face in
Next, place the base on a flat surface such as a
smooth table top. With the indicator quill contacting the surface the base is
sitting on, turn the dial face so the hand lines up with "0." Lightly tighten
the dial face lock so the dial will stay where you set it.
The pointed tabs over the dial face are for
setting upper and lower limits of measurements. Normally, for what we use these
indicators for, we do not use them, but you may.
Remove the barrel from the frame, and if the
extractor sticks out of the barrel too far, you may have to remove it also by
driving out the roll pin that holds it in. Punches are in the Tools section of
With the indicator zeroed and then placed on the
end of the barrel with a sized case in the chamber, it will then show exactly
whether the case head is below the end of the barrel, flush with the end of the
barrel, or by how much the case head sticks out of the barrel. Just be sure to
always watch what direction the indicator needle is moving, up or down, in
relationship to your "zero," i.e., the end of the indicator base/end of the
Note that the case head should never be below the
end of the barrel, even if the barrel is tight on a
.001" or .0015" feeler gauge blade, which is usually the thinnest blade in a
set. With a really close barrel-to-frame gap, the case head should be flush with
the end of the barrel and never below the end of the barrel.
Nor should the case head stick out more that what
the gap actually measures. The ideal is to have the case head stick out about
.001" LESS than what the gap measures.
I.e., if the gap is .003," then have the heads of
sized cases stick out .002." This gives a headspace of .001." Many folks don't
understand what headspace is. Here you see it. It is the actual distance, space,
between the case head and the breech face. If the case head sticks out MORE than
what the barrel to frame gap is, this is referred to as "negative headspace."
Having case heads stick out more than what the gap measures causes all sorts of
problems, and getting cases sized right cures the vast number of problems that
plague shooters of break open guns.
Summary of Headspace Conditions:
If the case
head is perfectly flush with the end of the barrel, the headspace will be what
the barrel-to-frame gap measures.
If the case
head sticks out of the barrel any at all, the headspace will be the
barrel-to-frame gap MINUS how much the case sticks out of the barrel.
If the case head falls below the end of the
barrel, add the distance from the end of the barrel down to the case head to the
barrel-to-frame gap measurement. This total is the actual headspace.
If the headspace is more than .006"
it exceeds SAAMI industry standards, and the condition should be fixed.
Headspace as it relates to
The greater the headspace, the more distance the
firing pin has to drive the case forward in the chamber until it comes to a dead
stop and the firing pin can expend its energy denting and firing the primer. If
too much energy is lost moving the case forward, there may not be enough energy
remaining to fire the primer even though the primer may appear well dented.
Thus, minimal headspace is mandatory not only for best accuracy, but even
useable accuracy and reliable functioning of the gun.
If the case head sticks out of the barrel more
than the barrel-to-frame gap measures, it prevents the barrel from closing all
the way and the locking bolts from traveling far enough under the frame's
"locking table" for an adequate lockup.
In Contenders, the result is that the hammer
block is not fully released so it can freely drop fast enough to clear the
hammer. The hammer knicks the top of the hammer block and even though it may
the primer, too much energy may be lost hitting the
hammer block to still fire the primer.
THIS IS ONE OF THE
MAIN CAUSES OF CONTENDER MISFIRES!
In G2s and Encores,
incomplete lockup due to the case sticking out too far prevents cocking the
Until now, there has been no convenient way for the average person to accurately
measure the distance the case head sticks out the barrel.
Worse yet, the vast majority of Contender and
Encore shooters don't have the foggiest notion about how to adjust the size die
to get the correct headspace. And the travesty is that those who do often
attempt to use SAAMI gauges, which in the real world is no where nearly correct
when hinge pin holes in barrels and frames vary as much as they do.
You HAVE to first know what the gap is then
MEASURE where the case head is situated relative to the end of the barrel. This
set up lets you do it accurately and easily, just like I have to do when cutting
the chamber and throat length to the correct depth.
You expect the chamber to be cut to the right
depth, but unless you can take the necessary measurements, you will never
consistently make the cases or loaded ammo the right length. The fact is that
with handloaded ammo the depth of the chamber is not important IF you make the
ammo fit the chamber. Precise measurements let you do this.
And if you shoot factory ammo, you still need to
measure the actual headspace since it is very common to see a "stacking of
tolerances" that create really excessive headspace resulting in misfires and
poor accuracy due to erratic ignition.
of a chamber on the deep end of the .006" tolerance limit, factory ammo on the
short side of the .006" tolerance limit, and a frame hinge pin hole on the
forward side of tolerances can result in headspace well over .010." And with
belt height variations on belted magnum ammo, headspace can be well over .016."
What happens when a round is
the firing pin has to
drive the case forward in the chamber until it comes to a solid stopping point.
This can be the case shoulder, the case rim, or the belt on a belted magnum
round. It takes
energy to move the round forward. The farther it has to be moved by the firing
pin, the less energy is left to fire the primer. If the distance is too great,
the primer receives a softened blow instead of a brisk strike... like getting
pushed with a pillow versus a quick jab with a stick.
If the strike from the firing pin is too soft,
primer ignition may be erratic or it may not ignite at all even if it is dented
pretty well. While a stronger hammer spring will usually stop misfires due to
excess headspace, the stretching of the cases that occurs can cause them to fail
quickly if they are reloaded.
Bellm Extra Strength Encore and G2 Hammer Springs
Correcting Excess Headspace.
If there is too much space between the case head
and the breech-face there are ways to correct it. This can occur with factory
ammo, new brass, or brass that has had the shoulders pushed back too far.
methods of correcting excess headspace
firing pin bushing forward, which may also require removing some material from
the end of the barrel,
Blow case shoulders
forward by first creating a shoulder on the neck for a headspace
point....successful if done right and there is ample support against the blow
of the firing pin,
Make cases by necking
down new cases with larger diameter necks, such as making .30/06 cases from
.35 Whelen brass,
Blow case shoulders
forward by using a compressed charge of slow powder behind a bullet jammed
hard into the rifling. This is for the advanced reloader and while 100%
effective, can be tricky, even dangerous if you don't think your way through
what you are doing,
Bend case rims forward
on rimmed cases,
Rechamber to a longer
cartridge, but get the chamber cut to the correct depth for proper headspace,
headspace is over .006" with factory ammo, return the barrel and frame to the
maker for replacement.
When adjusting size dies and seating dies, use the threads on your
reloading dies like a micrometer.
Think this through. You will find it invaluable.
A common micrometer is based on a 40 pitch
thread (40 threads per inch), meaning 1 inch is divided into 40 parts.
That is why the marks around the drum of a micrometer only go to 25. One
full turn, ie, one thread, equals 1/40th of an inch, or .025."
Size dies have a 14 pitch thread, so
dividing 1.000" into 14 parts gives .071" movement up or down with each
One half turn moves the die up or down
.0355.". One half of a half turn, i.e., 1/4 turn moves it half of
this, .1775." One half of 1/4 turn, i.e., 1/8th turn, is half this,
In the process of adjusting your size die, you can see
that once you are down that close, the dial indicator & base will let you
tweak the die very precisely for the final protrusion of the case head
from the end of the barrel that you are after.
Measuring seating depth:
Use the thread pitch of the seat stem in the bullet seating die like a
micrometer just like we described above for the size die.
You do not need to buy any gadgets or gimmicks to
measure seating depth. YOUR barrel IS the GAUGE. Here is how it works.
As with headspace, you MUST know what the
barrel-to-frame gap is. And you must either have the barrel off the frame or the
extractor removed if the barrel is left on the frame.
Make sure you have your cases sized correctly so
that they protrude from the chamber the correct amount. Then seat a bullet out
farther than anticipated. Drop the round into the chamber, and measure how far
it sticks out. The indicator base is counter-bored .100" deep for clearing the
protruding case head, so you want to work the seating depth down to where the
case sticks out of the chamber less than .100." (Early production indicator
bases were counter-bored only .050." We increased this depth for convenience
taking seating depth measurements.)
what the thread pitch is on the bullet seating stem. You can get a thread pitch
gauge from a hardware or automotive store, or you can measure one inch of thread
and count the number of threads in that inch.
Let's say you are using an RCBS seating die with
a 1/4"x28 thread pitch. Divide 1.000" by 28 threads per inch, and you get a
value of .0357" per one full turn of the seat stem up or down. Half a turn is
.0357" divided by 2 equals .0179." A fourth of a turn is .0089," and an eighth
of a turn is .0045." You should not only be able to estimate a half of a fourth,
1/8th turn, but also guesstimate finer adjustments still.
See how precisely you can tweak the seating depth
down to the point you get back to the same case head protrusion as with an
empty, properly sized case?
With the bullet touching the rifling and the case
head sticking out of the barrel the same amount as when empty, you now know
exactly what the relationship is between where the bullet makes contact with the
rifling and the breech face, allowing for .001" headspace. Remember, if you seat
a bullet out farther than this, your round will stick out of the chamber too
far, meaning, you will have lost the .001" headspace you established with a
Use the values you established for your seating
stem to determine how far off the rifling you have seated bullets.
You might want to keep one round with the bullet seated just to the lands and
other rounds marked with the amount of either bullet clearance from the lands
or, although I usually advise against it, save and mark rounds that stick out
MORE than the gap. These rounds will be your gauge for adjusting the seating die
if you want to engage the rifling a certain amount
Note in regard to erratic measurements of bullet seating depth:
If your bullets are canted in reference to the case body or
neck, they will not seat straight in the throat where they contact the ends of
the rifling, and thus they will bind up and not give uniform measurements.
inking the bullets will also show whether the rifling are touching uniformly
around the ogive of the bullet. You can get an inexpensive dial indicator stand
to position an indicator over your cases laid in a groove, such as a "V" block
(though a groove in a block of wood works also, for example). Turning the case
in the groove, the indicator is used to measure "run-out," or misalignment of
the bullet. If you find much run-out, then you need to take steps to cure it.
However, if the bullets do not go
straight into the throat of the barrel, they will bind up on their sides, and
not get consistent readings.
Erratic protrusion of sized
cases from the end of the barrel:
Note that as with bullets seated canted in the
case and giving erratic readings, you can also get very erratic readings from
your sized cases due to the expander ball pulling the case shoulders forward an
inconsistent amount, so do this:
1) Taper, smooth, and polish your expander balls, or get the
elliptical or carbide types.
2) Clean and lube the insides of your case necks before
3) Go to the full length bushing type dies sold by Redding, as
available, or have your full length size die retrofitted with neck bushings.
In any event, the headspace indicator will
measure and identify variations in headspace caused by the expander ball pulling
the shoulders forward inconsistently.
Measure the protrusion of a number of sized
cases, and you will find this is very true. Simply setting the lock ring on a
size die does NOT give consistent headspace. Sorry to bust your bubble if you
think your cases are all the same.
interesting experiment, measure the protrusion of a bottle neck case sized with
the expander/de-cap stem in place, then remove the expander/de-cap stem, run the
same case through the size die again, and measure its protrusion. If there is
much tension/drag at all on the expander ball, it will in fact pull the case
shoulder forward. How much depends on just how hard it is to pull the expander
back through the neck.
If you sort out cases that give exactly the same
amount of case head protrusion, you will also very likely find groups tightening
as a result.
Other factors the Headspace
Indicator can determine.
1) A very common problem occurs, and, again, it is one the
Headspace Indicator will precisely identify. This is the fact that many size
dies are purposely made too long inside so as to NOT push the shoulders of the
cases back past SAAMI dimensions. Particularly if the chamber is on the maximum
side of depth tolerances or if the expander ball pulls the shoulders forward too
much, the size die may not push the shoulders back enough to give the proper
case head protrusion less than the barrel-to-frame gap measures. In this
situation, the size die must be shortened, either by grinding some off the
bottom or "facing off" the end of the die with a carbide lathe tool in a lathe.
The tops of shell holders can be taken down for the same result, but this
weakens the shell-holder and makes it more prone to stripping out. Thus it is
best to shorten the size die itself and polish the internal edge as required so
there is not a sharp edge that will scrape brass at the mouth of the die.
2) Another item you can measure is the out of square condition
of the case heads caused by the end of the barrel (and/or chamber) not being
square to the breach face. Rotating the indicator base on a chambered round will
show the degree to which the case head is out of square to the end of the
barrel, and positioning cases consistently based on the high or low point on the
case head reading may also influence grouping.
(By design, Encore and Contender/G2 barrels drop
into the frame below square to the breech-face as clearly indicated by the fact
that when barrels touch the firing pin bushing, the rub mark is ONLY above the
chamber. This results in the bore and chamber line of the barrel being out of
square with the breech-face unless by random chance the chamber is misaligned in
the right direction and by accident is square to the breech-face.)
3) Monitor the relative
amount of force on the frame:
We find that loads that put a lot of strain on the frame often
do not shoot well. With the extractor removed, you can measure how far fired
cases are protruding from the frame at various pressure levels. The more force
there is on the frame, up to a point, the more the cases will stick out of the
barrel when fired. You may find that cases that stick out of the barrel, say,
.003" more after fired than before shoot better than those that stick out, say,
.005." Monitoring this can be valuable information in determining "sweet spots"
where a barrel shoots best.
Above a certain pressure load, the cases when
fired either slide back in the chamber or if the case wall adheres to the
chamber wall and pressure is sufficient, the case will stretch back to the
breech face. Higher pressures will also cause the frame to flex substantially.
Thus a case that perhaps sticks out .002" before firing may be sticking out
.012" after being fired. If you shoot a barrel with the extractor removed, you
will definitely see changes in the case head's position from before and after
firing. No values have been given to the amount of flexing of the frame that is
permissible/allowable, but once you establish your own value, short of
stretching and ruining a frame of course, you can use the headspace indicator to
measure how much the frame is flexing based on how much the case head protrudes
from the chamber after firing.
4) With the extractor
removed, another phenomenon you should be aware of and measure is the collapse
of the case shoulder when the firing pin hits the primer and drives the case
forward in the chamber. You can and really SHOULD take your properly sized
cases, prime them, then with the extractor removed from the barrel, fire the
primer in the primed case. Opening the barrel, you can now measure just how far
the firing pin has driven the case forward in the chamber.
If you push the shoulder on the case back too
far, then try it in the chamber WITH the extractor installed, you may find that
the extractor does in fact prove to be a headspace point even with rimless
For example, removing the extractor from .35 Rem.
barrels, I have found that often times they will not fire at all. The firing pin
simply drives the case into the chamber without firing it, or, if the chamber is
not super smooth, the fired case may remain substantially below the end of the
barrel. With the extractor installed, it will fire normally since the extractor
limits how far the firing pin can drive the case into the chamber.
Measuring rimfire ammo case rims for uniform thickness,
and, thus, uniform headspace.
"Mouse Gunners," rimfire "Smallbore" shooters,
have sorted ammo by rim thickness for years, but now can precisely measure the
actual headspace of rimfire barrels on break open guns as well as rim thickness
uniformity from round to round the same as with the gauges sold separately for
this job for years.
With the advent of the .17 rimfires, sorting by
rim thickness could prove beneficial to this venue also.
Measuring headspace in
straight walled, rimmed chambers.
The rounded tips on most indicator quills can be
unscrewed leaving a square end on the quill that can be used to measure the
depths of rim counter-bores in the end of the barrel. This has to be done
carefully so as to not twist the quill itself and bend the pinion shaft inside
the indicator. You must grip the quill part only from each end, meaning, DO NOT
hold the indicator body and try to unscrew the tip. You can ruin the indicator
The depth of the rim counter-bore can
be extremely valuable information to have. Measure the thicknesses of case rims
on straight walled cases. Then measure the depth of the rim counter-bore, add
the barrel-to-frame gap measurement, and subtract the rim thickness to derive
the actual headspace.
above, there are ways to reduce the headspace on case rims. One other method not
mentioned above is to peen the mouth of the chamber at the rim counter-bore.
This will move metal in the bottom of the counter-bore back usually a maximum of
.003" and can be sufficient to solve headspace problems very common to chambers
like .445 Super Mag that are usually deep enough to cause excess headspace and
early case separations.
As you can see, there are a myriad of things the
Bellm Headspace Indicator set up can measure.
In the process, you will be able to tell
precisely what is going on in your break open guns. You can get a "handle" on
what produces best accuracy and what doesn't, or in the case of frame flexing,
you can establish a standard for the amount of flexing your maximum loads should
produce, past which you don't want to go, thus establishing your own maximum
pressure "redline." Note that no printed instructions are being sent with the
indicator bases or complete setups, so I suggest you print out this page for
If you have not gotten the Bellm Headspace
Indicator Base, you really do not know what you are doing. Unless you are using
a difficult to use and expensive depth micrometer, there is no way you can know.
For years we guessed, if we even thought about it. Now we can get truly "dialed
Stop shooting in the dark. Know PRECISELY how
your cases are sized and how your bullets are positioned in the throat with the
Bellm Headspace Indicator!