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|LENGTHENING SHORT BRASS TO FIT
YOUR BPCR CHAMBER
By Wayne McLerran
Lengthing Brass with a Lathe
If you’re fortunate to have a lathe or a friend that has one, brass can be
lengthened using a “nib & spin” technique. The process involves the use of a die
to hold the case and a “nibbing rod”. The nibbing rod is similar to a boring rod
but has a very smooth hardened bump on one side close to the end, or has a
hardened ball bearing seated on one side to form the bump. A die, similar to a
full-length resizing die, is constructed to rigidly house the case and hold it from
turning. The die inside diameter (ID) must closely match the outside diameter
(OD) of the case. The die and case are aligned and clamped in the chuck jaws.
Once everything is setup, the nibbing rod is inserted deeply into the case at a
point where the case wall is thicker. As the lathe is running the rod is adjusted so
that the bump or ball bearing presses against the wall of the case and slowly
“irons out” (thinning) the wall as the case spins and the rod advances towards the
case mouth, hence the term “nib & spin”. As the wall is thinned the excess brass
is forced forward lengthening the case.
The following photos were provided by Mike Deland, aka mdeland. Starting with
a Remington .45-70 case on the left, the resulting two long cases in the last photo
required at least three nibbing passes, possibly more for the long one on the right.
The middle case finished up at a very even neck wall thickness of 0.009”.
Note – New Remington .45-70 cases have typical neck wall thicknesses of
0.010” to 0.011”.
Last update: 3/13/17
In another article posted on this site titled Shooting Short-Case Straight-Wall
Black Powder Cartridges – Myths & Facts Concerning Chamber Rings &
Accuracy, I discussed the subject of firing “short-case” ammo. The bottom line
is it will not damage the chamber but expect accuracy to suffer to some degree.
In another article titled Determining Case Lengths, I covered several techniques
to determine the exact length of your chamber and the preferred overall “fire-
formed” case length. So, assuming you've measured the chamber and determined
that the bunch of expensive brass you have is too short, what are your options?
You could purchase new brass, which may not solve the problem. The chamber
may be longer than available new brass or longer than specified by the Sporting
Arms and Ammunition Manufacturers’ Institute (SAAMI). And even if your
chamber is SAAMI compliant, it’s very common to find new factory brass
shorter than the SAAMI specifications. Of course, assuming it’s available; you
could buy new brass for the same caliber but for a longer chambering and trim it
shorter. An example is buying .45-90 brass to use in a .45-70 chamber after
trimming. But this article is not about buying new brass. I will cover the three
techniques that I’m aware of to lengthen the cases you already have.
Prior to discussing “realistic” options for stretching or lengthening cases I’d like
to dispel any thoughts you may have of attempting to significantly stretch brass
using unorthodox loading or chambering techniques. Brass can be “fire-
stretched” by using a combination of heavy neck tension, crimping the bullet and
lubricating the chamber wall, but it will take several firings to stretch it a
significant amount. Plus the likelihood increases that the case will completely
separate. I suggest you read the article I wrote some time ago titled Case
Stretching & Separating In Black Powder Cartridge Rifles.
Case Stretching Options
Note - Should you succeed in stretching brass using one of the techniques
discussed below, keep in mind that the ideal case overall length (COL) should
match the overall chamber length after “fire-forming” and/or neck expanding,
certainly prior to full length resizing which will lengthen the case a few thousands.
Tim Smith-Lyon’s Case Stretcher
For a simple and relatively cheap solution, Tim Smith-Lyon designed and
manufactures a case stretcher that screws into a RCBS resizing die in place of
the decapping rod. The thread on the stretcher stem is 1/4-28 which is
compatible with RCBS' die. Two versions of the stretcher are available for .40
caliber and .45 caliber brass, and can be purchased from Buffalo Arms. For an
instructional video of Tim using the stretcher go to http://www.youtube.
com/watch?v=rJQVNTvj5Lw. The current price is $39.95 plus shipping, and
you will need a RCBS full-length or neck only resizing die.
I’ve used the .45 caliber stretcher and it works as advertised, but it’s more work
intensive and not as fast as the Kal-Max jig discussed below, but much less
expensive. Also, I strongly encourage you to anneal the necks prior to and after
stretching. Annealing will result in easier stretching, nullify the work hardening
of the brass induced by stretching and reduce the possibility of future case
separations. Following the instructions, many strokes of my Redding T-7 turret
press were required to stretch new .45-70 Remington brass 0.010”. One has to
definitely develop a “feel” for when the stretching is taking place. The brass is
stretched in the neck region. The process not only uniforms the neck wall but
also thins the neck wall slightly, which may or may not be an advantage
depending on your chamber and bullet dimensions. The Remington brass neck
wall thickness went from 0.0105” to 0.0095” as the case was stretched 0.015”.
Continuing the process, I was able to stretch annealed cases 0.030” with a
resulting neck wall thickness of 0.0090”. Additional stretching may be possible,
but I quit after reaching 0.030”. Tim suggested that the max he would
recommend stretching Remington brass is 0.025". He also indicated that a liberal
amount of case lube, more than would be used just resizing the brass, makes the
stretching noticeably easier. Tim uses RCBS water soluble Case Lube-2. I used
what I had handy, which is RCBS's original case lube (not water soluble).
Kal-Max Case Stretching Jig (KMCSJ)
If your short brass is Remington, Starline, Winchester or Bell brand in .38, .40 or
.45 caliber, another option is to purchase the Kal-Max Case Stretching Jig. I
highly recommend the KMCSJ for stretching brass, but considering the price
($185 + shipping at the time of this writing) plus the additional hydraulic pump
and ram unit ($100 to $250), it may not make sense to purchase the setup to
stretch a hundred cases or so. Once the jig and ram are set up and adjusted, the
stretching process is relatively fast. For a short video showing the KMCSJ in
actual operation go to http://www.youtube.com/watch?v=oGzQsrPT4Qs or
http://wn.com/Kal-Maxavi. The hydraulic pump and ram (the two orange-
colored units in the video) are not included with the KMCSJ and must be
purchased separately or rented.
For pricing and more details on the KMCSJ, go to http://kal.castpics.
net/CaseStretcher.html or contact Charlie (Chuck) Maxwell (aka Montana
Charlie) at email@example.com. There’s more than one source of a suitable
4-ton hydraulic pump and ram. Porto Power makes one (also sold by Sears), but
the best deal I found is the Central Hydraulics Portable Puller (model # 44899)
from Harbor Freight. I picked up one on sale for significantly less than the
regular price of $99.99. You may also be able to rent one from a local
equipment rental company.
Using the KMCSJ, I stretched brand new .45-70 Remington brass 0.008” at the
minimum setting and 0.037” at the maximum setting. The potential stretching
range depends on the wall thickness at the central portion of the case. Within the
total range the amount stretched is determined by the adjustable punch. The
punch comes with several thin washer-like spacers. Maximum stretching is
achieved when the punch, with no spacer, is seated as deep as possible in the
case. Due to the tapered walls of the case (walls get thicker towards the rim) the
deeper the punch seats in the case the more it stretches the case as the punch and
case are forced through the die. The finished brass no longer has tapered walls
where it was stretched, which was typically in the middle of the case. The case
wall thickness in the neck region is not changed.
The initial brass I stretched was not annealed, but all subsequent brass was
annealed prior to and after stretching where the stretching was taking place on the
case body. Although many shooters using the Kal-Max do not anneal prior to or
after stretching I suggest 1st determining the location where the brass is being
stretched and anneal accordingly. Annealing will result in easier stretching,
nullify the work hardening of the brass induced by stretching and reduce the
possibility of future case separations. Certainly, annealing the middle of a case
and ensuring the retained heat does not anneal the head area can get tricky. I
lined up the cases in a shallow pan with water covering the head and annealed in
a dark room with two hand-held torches. Holding a torch in each hand, I moved
down the row heating both sides of each case at the same time.
Kal-Max versus Tim Smith-Lyon’s Stretcher
As noted in the above comments, the price, complexity, and the stretching
process are different between the two solutions. Also, the location the brass is
stretched is different. As displayed by the dark case discolorations in the
following photo, the Kal-Max stretches the brass in the middle; the Smith-Lyon’s
unit stretches the neck area. By the way, the discolorations were the natural
result of brass oxidation over several months after being stretched. The
discolorations will be easily removed during normal cleaning in a vibrator or
Wishing you great shooting,