What a difference just an eighth of an inch makes.

Recently I came across on a surprisingly good deal on a Taurus Tracker .44mag snubnose. This one:

Taurus isn’t my first choice of firearm brands, but I’ve owned them and generally liked them, and the price on this one was a little too good to pass up. So I got it, figuring that it would be an interesting addition to my collection, occasionally using it as a carry gun.

After shooting it with a variety of .44special and .44mag loads that I had on hand, I decided that what I wanted to use as a carry ammo was something we’d tested: Corbon’s 165gr JHP.  The lighter weight bullet would mean a lower felt recoil. And I knew how it would perform out of a short barrel, and estimated that I would get about 1150fps and just under 500ft/lbs of muzzle energy from the round. I checked locally, and the ammo wasn’t available, so I ordered in five boxes from a source online.

When it arrived, I did the logical thing and inserted five rounds into the Taurus, then closed the cylinder.

Er, make that I *tried* to close the cylinder. Because it wouldn’t. Huh?

I examined the gun. I had not noticed that the cartridges hadn’t gone completely into the chambers. The rims of the cartridges were all about 1/16th inch out.  Oops. That was a mistake on my part — I should have been paying closer attention when handling the new untested ammo, rather than just assuming that it would load properly. This is what it looked like after I removed one cartridge for contrast:

 

Even lightly tapping the cartridges wouldn’t get them to load properly (where the rim is down on the rear cylinder face). I removed the rest of the cartridges, examined the gun to make sure everything was otherwise functioning properly. It seemed to be. I looked over the cartridges, and they seemed to be fine, as well. So I got a couple of different .44 loads — a mix of .44sp and .44mag — and put them into the cylinder. They all loaded just fine, the cylinder closed, and there were no problems. Here are a Hornady and a Winchester .44mag round in the cylinder, with one of the Corbon; note the difference:

 

Hmm.

Next, I got my Colt Anaconda .44 out of the safe. I tried the same ammo in it, and this is what I found:

Exact same problem. So, presumably, it was the Corbon ammo. I removed the rounds from the gun.

And grabbed my digital calipers. I started checking all the dimensions on the Corbon ammo. In fact, I went through and checked several sample cartridges from all five boxes. As far as I could tell, everything was in spec. The cases were the exact correct length. And width, both at the mouth of the case, along the body, and just above the rim. The bullets were the correct diameter. And the over length of the cartridges was well within the normal range of .44magnum rounds.

WTH?

I set the conundrum aside, so my subconscious could chew it over for a few hours. The likely explanation hit me while taking a shower the next morning. Here, look at the images of the three different rounds mentioned above, and see if you can spot it:

Here’s a hint: the Corbon cartridge is in the center.

Got it?

Yeah, if you look very carefully, you’ll see that the SHAPE of the Corbon bullet is different than the others. Note how it almost swells a bit, going up from the mouth of the case, to about an eighth of an inch, before narrowing down. Whereas the Winchester (on the left) and the Hornady (on the right) both have a smooth ogive right from the mouth of the case until coming to a flat nose (actually, the Hornady, like the Corbon, is a hollow point, but you can’t see that from this image).

So why did this cause the problem?

The explanation requires a bit of detailed knowledge about how a revolver works. If you already know all this, my apologies. For those who may not …

Each chamber in a revolver has to be big enough to accommodate the case of the cartridge. But the bullet is slightly smaller than that, so that it fits inside the cartridge case.

Now, when a chamber on a revolver rotates into position aligned with the barrel, there’s always a chance that it might not be perfectly aligned. Just a few thousandths of an inch misalignment can lead to all kinds of bad things happening, from parts of the bullet being shaved off and spit out the sides of the ‘cylinder gap‘ to the gun going KABOOM in your hand. So revolver manufacturers have come up with two nifty ways to deal with this:

1. Narrowing the chamber in front of the cartridge case slightly by tapering it.
2. Having a ‘forcing cone‘ before the barrel that is just a little bit bigger than the bullet, to funnel it into the barrel.

So, the problem with the Corbon ammo was that shape of the bullet in the pic above. Note how it doesn’t smoothly curve in like the other two bullets. Rather, that slight swelling is probably hitting the taper inside the chambers, stopping the cartridge from seating properly.

And before you say that this is a problem with the Taurus being poorly made, note that I ran into the exact same problem with my Anaconda — widely considered a very good quality gun.

Now, the folks at Corbon are smart. I’m sure their engineers actually tested this ammo in some typical .44magnum revolvers. But all it would take is for slight differences (think a couple thousandths of an inch) in the rate or position of that chamber tapering from manufacturer to manufacturer to cause this problem. Chances are, they just didn’t test it in a Taurus .44 of this model, or a Colt Anaconda. It is also possible that this batch of bullets (all five boxes I got are from the same lot — I checked) is just slightly out of spec, but no one has yet noticed it in their guns, because the tolerances in other manufacturers are a little bit different.

Either way, I’m fairly sure that I could just take some sandpaper or a fine file to that slight swelling on the bullets, and they’d fit right into my gun. But first I’m going to wait and see whether I hear back from Corbon about this issue (yeah, I sent them an explanatory email a couple days ago).

Oh, one last thing: in the process of going through all of this, I noticed that the cylinder length (from the front face to the rear face of the cylinder) on the Taurus was 1.625″, or 1 5/8″, whereas the cylinder length on my Anaconda is 1.75″, or 1 3/4″ — an eighth of an inch difference. As I recall, 1.75″ is standard for .44magnum revolvers. Interesting that the Taurus is slightly shorter, and that may indeed have had something to do with the shape of the chambers on the gun.

Edited, 2/27: Just a quick note. I’ve had some friends check other brands of .44mag revolvers. Seems that Smith & Wesson makes theirs with a cylinder length of 1.6875″ (1 11/16th”), and Ruger 1.75″ (1 3/4″). So there’s more variation than I thought.

 

Jim Downey