Bullet Sizing:

Fit To Barrel Or Cylinder?

When it comes to factory ammunition or reloading with jacketed bullets we really have very little choice when it comes to bullet diameter. However, if we cast our own, and consequently size and lubricate the bullets we have molded, we can tailor the diameter of the bullets to suit our particular sixgun.

For example, I have sizing dies for the .44 Special/.44 Magnum running in one-thousandth inch increments from .427″ to .432″ and for the .45 Colt from .450″ to .454″. When I first started making my own bullets one at a time from a single cavity mold and then tapping them through a sizing die using a wooden dowel, I simply used .358″ for .38 Special/.357 Magnum and .454″ for .45 Colt. I never bothered to measure anything on my Ruger and Colt single action sixguns and didn’t have the proper tools anyway.

As I acquired more experience, my operations became more sophisticated. Early on I learned about slugging barrels and barrel size differences in Elmer Keith’s book Sixgun Cartridges and Loads. I accepted what he said as gospel and I spent several years finding the groove diameter of my sixguns by tapping a soft lead slug through the bore and then measuring. That was Keith’s observations going all the way back to the 1930s.

A Waste Of Time?

However, after all these years I decided — why bother? After spending too many years slugging barrels I decided it was a waste of my time. I finally came to realize, after some careful thought, I was missing what Elmer Keith barely touched on. Namely, cylinder throat diameter. Keith was only concerned the throats were not smaller than the barrel diameter. Just like Elmer (and Duke, in his March/April 2012 article) I carefully measured to find barrel diameters, but now I find myself on the verge of sixgun heresy by disagreeing with not only my good friend Mike — but also the Old Master himself.

Mike and I both have decades of experience shooting sixguns, leverguns, black powder arms, and single-shot rifles. I would guess I shade him when it comes to sixguns, while he leaves me in the dust with single-shot rifles. We are good friends, we learn from each other, but we certainly don’t always agree with each other.

Here is my point. Suppose I carefully slug the barrel of my .45 Colt sixgun and find it to be .451″. I carefully cast, lube, and size my bullets to .451″ and then equally carefully tailor my cartridges. When I shoot these meticulously made .45s through my Colt results are mediocre at best. Why? I did everything right. Well, almost. I carefully measured the groove diameter, however I neglected the cylinder throats, which on further examination by carefully measuring with pin gauges of the proper diameter, I find are a uniform .454″. So what happens when my .451″ bullets hit the front of that chamber? What happens to a bullet when its base is hit with 15,000-20,000 pounds of pressure? It expands. And what does it expand to? The size of the cylinder throat. So the bullet I carefully sized to .451″ is actually much larger when it hits the forcing cone.

Since the bullet is going to be turned from .451″ to .454″ under pressure, wouldn’t it be much better if it was already that size when we hit the switch? If the bullet is undersized it may swell up perfectly or it may not. If it’s already tailor-made to fit the cylinder throat it will enter in perfect alignment with no distortion.
By John Taffin

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