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TO RESIZE OR NOT TO RESIZE
By Wayne McLerran
Updated: 7/28/13

Resizing cartridge cases will work harden the brass and increase the chance of it
eventually splitting or separating, but there are other good reasons for minimal
resizing or not resizing at all.  Following is my viewpoint on the subject.  While
reading further, keep in mind the discussion is for black powder cartridges for
single-shot rifles, but most of the comments will also apply to smokeless ammo as
well.

As with just about every subject there are pros and cons to consider.  If the ammo
is used for hunting it’s a good idea to full length resize for adequate bullet neck
tension and to ensure the cartridge easily slides into and out of the chamber which
may be slightly fouled from previous shots.  If the ammo is being fired in more

than one firearm, full length resizing is also recommended to ensure the cartridge
will fit chambers with slight dimensional variances.

Although long straight-wall cartridge cases can stretch, especially those using
compressed powder, if the firearm uses a bottleneck cartridge, due to the shoulder
the case is more likely than a straight wall case to stretch when fired.  For
additional discussions on the subject see
Case Stretching & Separating in Black
Powder Cartridge Rifles.  If the case does stretch, full length resizing will not only
reduce the diameter of the main case body and neck but also set the shoulder back
slightly.  The result is that some of the brass will be forced to the neck by the
resizing die, lengthening the neck and the overall case.  Sooner or later the case
neck will need to be trimmed.  Therefore, each time the case is used and full-length
resized, brass migrates from the main body to the neck, thinning and weakening the
main body of the case, eventually resulting in case separation, typically in front of
the thick region forward of the rim.  This is better understood by high velocity
smokeless shooters but also applies to black powder cartridge shooters, only to a
lesser degree.

It’s always been my viewpoint that, for maximum accuracy, the dimensions of the
loaded cartridge should match the chamber and throat dimensions as close as
possible, resulting in minimal bullet expansion and distortion and maximum
alignment with the chamber and bore.  Therefore, if the brass is being used in only
one firearm, the best practice is to never full-length resize after initial firing,
commonly referred to as using “fire-formed” brass.  But depending on several
factors including dimensions of the bullet, chamber neck, throat and bullet seating
depth, minimal neck resizing may be necessary to hold the bullet under slight
tension and proper alignment.  For those shooters, and I count myself as one of
them, that “slip-fit” the bullet by hand with very little or no neck tension, some
neck-only resizing may still be necessary for bullet alignment.

If done properly, annealing (heating the brass to soften it) can reverse work
hardening of the case neck, but for safety reasons is definitely not recommended
for the main case body.  For more details on annealing, see to the article titled
Annealing BPCR Case Necks.



Wishing you great shooting,
Wayne