Mushroom Free 6XC
11-13-2005 Update | 11-18-2005
Update | 11-28-2005 Update | 12-17-05
Update | 2-10-06
Update | June 2006
To all 6XC users, here is a mushroom free process to
any brand of 22-250 Cases into 6XC Cases. Best of all, you most likely
will not require anything extra. Odds are you have everything you need
mushroom free process already. This
mushroom free process does however require one extra step. This extra
step bumps the shoulder on the
22-250 case at a 20-degree shoulder angle using a 308 full sizing die.
Odds are anyone loading a 6XC has a 308
full-length sizing die.
The 6xc case requires that the shoulder on the
moved back 0.064 inch for the 6XC
design. Take a 22-250 case and drop it
into a 308 full
sizing die. The 22-250 case should
almost completely fit into the 308 die. You
should notice that only 67% of the rim thickness on the 22-250 case is
above the very bottom of the die.
measured this on some once fired
22-250 cases to
be 0.033 inches. The 22-250 case shoulder is
smaller diameter than the 308 case. The
22-250 case easily fits into the 308 die sizing die. The 22-250 case
shoulder is contacting the
die. This shoulder must be moved
back 0.064 inches. The
22-250 cases I measured had the bottom of the cases sticking up 0.033
the bottom face of the 308 die. You must
now move the 22-250 case into the 308 die an additional 0.031 inches
order to achieve the 0.064 in shoulder set back.
cannot do this using a
holder. However, you may modify one of
your extra shell holders to perform this pre-bumping operation. All you
need is a couple of flat washers and
modified one of my extra shell holders
washers. One flat washer about the same
diameter has the shell holder and one smaller brass flat washer. The
smaller flat washer must easily fit into
the base of the 308 full sizing die. I
happen to have a small brass washer that was about 0.033 thick. After
sanding it with some 400-grit paper for
good glue adhesion, I continued sanding to obtain the 0.031 thickness.
Then I epoxy the two washers on top of a
spare shell holder. Note: before the
epoxy hardens completely, place the 308 die, shell holder into your
make sure the small little washer easily fits into the sizing die or
have to chisel things apart and start over. Machined shell holder
for pre-bumping 22-250
all you have to do is place a 22-250
washer and run the case up into the 308 die. This will bump the 22-250
case shoulder back at the 20-degree
angle. After pushing the 22-250 case
into the 308 die, the case should come out as you lower the ram. No
lube required for this shoulder bumping
is it; now just process the 22-250
cases in the
dies. The 6XC die will expand the
neck to 6mm while lengthening case neck making the 30-degree case
shoulder. The cases done using this
pre-bumping mushroom free process will be slightly longer then the
process. The formed case necks are
longer while the case shoulder is smaller diameter. The case shoulder
will expand during fire forming. I cannot give you any fired case
results. My Tubb Gun is on order. I have received my 6XC die set and
one of the once fired 22-250 Winchester
cases without pre-bumping the case shoulder back. This
formed 6XC case had the classic shoulder
mushrooming, or penis head. So if the
mushrooming appearance when making 6XC cases from 22-250 bothers you
here is an
extra step mushroom free process. When I
finally get to the range with my new Tubb Rifle and folks come by to
see it, I
will not be showing them any little dick headed cartridges.
From Left to Right
22-250 Case -
Once Fired Winchester
shoulder pushed back using 308 Die
6XC Case Formed
after prebumping shoulder back
Mushroomed 6XC formed using
just the 6XC Die
Mushroom Free Process
1. Formed necks
are longer and closer to
6XC design length
2. Cases necks
appear to be more
3. Turning necks
after 6XC forming may
yield less donuts
4. Cases look
better before fire forming
should be easier, just expanding the shoulder out. You
are not trying to smooth out a reverse wriggle in the case shoulder..
6. Case trimming
may be required at some point
speaking backing the shoulder down the 0.064 is wrong
or slightly too
much. The shoulder diameter on the 22-250 case is 0.414 in
diameter and the case side slope is something like 57.16 to 1.
the shoulder diameter on the set backed 22-250 case should be about
0.4162, which is still much smaller than the finished 6XC shoulder
diameter of 0.455 inches. Therfore, the bumped shoulder on
22-250 with the smaller diameter shoulder should sit about 13
higher into the 6XC forming die than finished shoulder after
fire forming. Therefore, the total amount of pushing into the 308
be closer to 0.051 thousandths than 0.064 thousandths as mentioned
above. I have tried one 22-250 with a 20 thousands washer and it
worked without any mushrooming and had a more pronounced 30 degree
shoulder. The magic number may be 18 thousandths, anything less
than 16 thousands I have gotten mushrooming. The math on this
will drive you nuts. Just
remember the main point here is 22-250 cases may be prebump and then
formed using the 6XC die and not have any mushrooming on the case
head. Anyone doing this should run a few test cases for the
prebumping which will work best with your brass and fired
chamber. The one 22-250 once fired case I tried with no washer or
just pushed the case flush to the bottom of the 308 die still
mushroomed. I will mention again that I do not have my Tubb Gun
yet to work out correct amount of set back for my chamber.
Hopefully by the time
I get my Tubb Gun, enough of you other Tubb 6XC users will have tried
this and have some actual prebumping barkpark numbers for new 22-250
brass from various manufacturers.
Case length. This process also produces longer necks on the
formed 6XC cases. In fact you can control the case length.
The amount of pre-bumping will affect the overall case length. As
you approach the minimum amount of pre-bump for a mushroom free case,
overall length of the case reduces. I am going to use a pre-bump
that will yield me an overall case length that is slightly above the
trim to length of 1.900. This will allow me control the
length of the case neck before neck tuning. Just trim all the
long range cases before neck tuning. I have received my neck
turning and neck expanding mandrels. While turning a couple of
mushroomed cases in notice excessive wobble in the neck while holding
the neck turning tool. I did not notice this on any of the
non-mushroomed cases that I neck turned. The mushroomed cases
with the wobble were not evenly mushroomed, i.e., they were mushroomed
more on one side than the other. These cases caused the
neck-turning tool to wobble in my hand. Therefore, the
pre-bumping process may
produce more concentric cases.
I have received my 500 Winchester 22-250 Remington cases so I
may now start
making my 6XC cases. My goal is to have mushroom free 6XC cases ready
when I get my Tubb Gun. I have sent some formed cases to a friend that
has a Tubb 2000
to measure and compare to his fired cases. This will give me a starting
point for my die set up. My first attempts at making 6XC cases using
22-250 brass indicated that I may have some control over the final
case length. Therefore, I would like to have the formed 6XC pre-fire
cases just over the trim length of 1.900 inches. I would like to have
cases before neck turning.
I plan to use the Redding competition shell holders in all die
set-ups. I will start with the Plus 10 Shell Holder and see what I get
using the 0.268
Tubb bushing. I screwed the 268 bushing down tight as I could into the
die and locked it. I also screwed the 6XC die as hard I could use
and a small piece of leather so not to mar the die to the top of the
with the plus ten-shell holder. If I change shell holders, I will
tightening the die down hard on the new shell holder.
Using the 0.268 bushing the first case I pre-bumped using a 16
washer. The first new case had some slight
mushrooming. The case measured 2.068 inches with my Tubb Gauge with an
overall length of 1.900. My target headspace
dimension is 2.064 inches with an overall dimension around 1.904
inches. I was able to get 1.908 with some of the once
fired cases. Therefore, I am hoping for the overall case length to be
just long enough to do some trimming on. Next, I tried the plus
on the same case and ended up with 2.0615 inches for the headspace
measurement. I should have tried the plus eight
first. The next case I changed to a 20 thousands washer and back to the
plus ten-shell holder. The table below shows
the various washer thicknesses and shell holders sizes I used to
achieve the various
Now I have come back to the 0.031 thousandths washer and time to see
cases will chamber okay. Now off to friend house with Tubb Gun to test
above cases. I think the cases using the plus 0.010-inch
shell holder are to long, however, I am hoping that the cases may still
chamber okay since they are slightly long just at the very top of the
shoulder. The cases using the plus ten shell holder
chamber okay. There was some resistance.
However, if I did not try the bolt on an empty chamber first I would
not have noticed it. The resistance was minimal. I also measured his go
gauge with my gauge
bushing and some fired cases.
Cases numbered two through eleven were pre-bumped using a 0.020 washer
shim washers to change the amount of pre-bump. Cases numbered 12 where
done using a new 0.031 thick washer
glued on top of the flat shell holder. I did five
cases in all with the new washer to check the variances in gauge length
and overall length. Everything looks like a go for these
Picture of finished cases below.
The basic procedure I used to form 6XC brass from 22-250 brass is as
Step one - Pre-bump the 22-250 shoulder using the 20-degree shoulder
of a 308 win full sizing dies. I used 0.031-inch
think washer to push to 22-250 case slightly into the 308 die. No lube
was required and all but two of the
500 cases fell freely out of my Redding 308 full sizing die. Two
required a tap with a pipe cleaner to get started.
Step Two - Form 6XC cases using the Tubb 6XC sizing die with the 0.268
bushing. I also used the Redding Plus
0.010 inch competition shell holder. Gauge length of formed cases
Step Three - Expand necks using K&M expanding 6mm mandrel.
Step Four - Trim cases to 1.900 inches. I
modified a 243 Lee Trimmer.
Step Five - Inside taper and de-bur neck using K&M 7 degree taper
tool. I chucked the case in my hand lathe and then
used the K&M 7-degree taper tool. Doing this before neck turning, I
think it helped the flute
the neck-turning tool enter the cases easier.
Step Six - Turn necks using K&M Neck Turning tool. I
set the cutter for 0.012 cut wall thickness
using feeler gauge. Lightly de-bur
outside of case mouth and steel wool case mouth end. First tried
thousandths and completely missed the neck. Thirteen thousandths
setting cut some of the neck but not enough. The twelve-thousandths
setting looked good
and I stayed with it.
Step Seven - De-bur flash hole inside case using K&M tool and
drill. Just made sure that the K&M
tool would easily rotate in the flash hole and do it with the letter B
drill. I notice some of the holes had burs on the inside of the hole
and required to
be drill out with the
K&M tool. The letter drill cuts a
118-degree angle and not a 60-degree angle like the K&M tool.
Step Eight - Uniform the primer pockets. No,
I will be using the K&M primer pocket uniformer to clean the primer
pockets after firing and after about three firings, it will stop
just clean the primer pocket.
Step Nine - Solvent Rinse, three stage process.
Step Ten - Sort by weight and box in MTM-100 boxes.
Box One - 156.7 to 157.4 grains
Box Two - 157.4 to 157.8 grains
Box Three - 157.8 to 158.4 grains
Box Four - 158.4 to 159.1 grains
Box Five - 155.7 to 156.6 grains plus 159.1 to 161.0 grains plus cases
to develop process and three with fixed rims.
Thirteen of the new cases had split necks out of the bag.
Now the big wait begins. I am going to have
to get some fired cases to practice on next.
Case Forming Summary
The 0.031 pre-bump worked allowed me to trim almost all of the cases
some. While most cases just a partial cut, it was
enough for a good stop during the neck turning process.
No lube required during the pre-bump step and I only lube the case neck
inside during the 6XC die-forming step. I
slopped enough Imperial Wax on the neck outsides to keep the neck
The Winchester brass seemed to have consistent neck wall
thickness. The 0.012 wall cleaned up all
the cases. The few I set aside for
incomplete cut, I sorted by weight back into the
whole group. For all practical purposes,
they were 100 percent cut. I did not have any lopsided cases, just a
photo of 6XC shell holder. Works like a charm. The only alteration is
the width of the extension area which is 9.6 mm in diameter. (Why 9.6
mm - because that is the diameter of a .223 case rim - also no problems
with "stuck" cases due to die contact with shell holder). Why don't you
add this to your 6BR article as an update. Notice on the far left is
the original mushrooming of the 6XC. The two cases on the right are
using your method. Chambering is perfect and your height dimension is
optimal. A picture paints a thousand words.
Here is a picture of the final washer constructed Shell Holder I used
to pre-bump the shoulder on the my new Winchester brass. Washer
height is 0.031 inch. The shell holder was
filled with epoxy under the washers to prevent any dimpling of the
Great to have a friend with a lathe. Here is a picture of a very
nice machine shell holder made to pre-bump the 22-250 cases.
Height of pre-bump is 0.036 inch.
I finally got my Tubb Gun and here is a picture on a fired case next to
a loaded muchroom free case. Cases are fire gorming complete
using 35 grains of H4350 and bare Sierra 107 MatchKings. My fired
cases are only three or four thousandths shorter.
Picture below shows a loaded Mushroom Free case that I resized for 6XC
alone side a fire formed and resized case.
Using my Top-Secret Pattent Pending Inspection Lighting Systems, allows
you to see minor changes in surface contours. Note the small cut
in the top of the shoulder on the Mushroom Free Case on the
right. That small portion of the case is actually a few
thousandths longer in headspace and chambers easy. The small
portion on the base of the neck not neck sized is barely visible on the
resized case on the left. The little bumping on the shoulder is
also using the lighting system.
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