Ballistics by the inch

Shooting big stuff.

Ever hear of a 4 Bore?

Here’s the first line from the Wikipedia entry:

Four bore or 4 bore is an almost obsolete black powder caliber of the 19th century, used for the hunting of large and potentially dangerous game animals.

The term “4 Bore” indicated that it would fire a sphere of lead weighing 4 ounces, or one-quarter of a pound of lead. This was an old measurement system from which we also get our shotgun gauge measurements: a 12 gauge shoots a sphere of 1/12th a pound of lead, etc. So, a 4 Bore shoots a sphere of lead that is three times the weight of what a 12 gauge would shoot. As in a ball 1.052″ diameter that weighs 4 ounces, or 1,750gr. Compare that to a typical 12 gauge slug, which weighs from one to 1.125 ounces. The 4 Bore ball is more than three times the weight.

And shooting one feels like it.

Well, depending on the black powder load, of course.

Here’s the one we shot, the Blunderbuss on the right:

And here’s looking down the muzzle:

As the maker of the gun notes:

This 4 bore Blunderbuss can be pretty intimidating when you’re looking down the end of one.

Especially when the end is TWO inches in diameter and the bore is more than one inch too!

The thought of shooting it was pretty intimidating, too.

The maker recommends a load of just 100gr of Fg black powder. So that’s what we started with. Here’s what that looked like, being shot by Jim K of the BBTI team:

Not bad, right? Yeah, it felt like shooting a typical 12 gauge loaded with slugs. Of course, the Blunderbuss doesn’t have a modern firearm design, with no mechanism to reduce recoil.

And here’s my friend Roger shooting it with the recommended load, in slow motion:

Now, Roger’s a big guy. Over 6’6″. And like all of us who shot the 4 Bore, he has decades of experience shooting all manner of long guns, from mild black powder muskets to modern heavy magnums. Now just watch what happens when we increased the load in the 4 Bore to 200gr of Fg black powder:

And here’s Keith of the BBTI team shooting the 4 Bore with that full 200gr load:

Impressive, eh? I don’t have video of my shooting it, but I do have the bruises to prove I did.

Well, now, think about this: historically, these guns were loaded with up to 500gr of black powder. Bloody hell.

OK, let’s talk ballistics.

See the orange thing in the foreground in most of the video? That’s a LabRadar ‘chronograph’. It said we got about 500 fps from the ‘light’ loads, and about 700 fps out of the ‘heavy’ loads. That would give us a muzzle energy of about 970 and 1900 foot-pounds, respectively.

Your typical 12 gauge slug has a ME of about 2600 ft/lbs.

So, what gives? Why does the 4 Bore look (and feel) like it had so much more power?

I’ve been thinking about this for the last several days, and I think the answer is that a heavier bullet gives you more perceived recoil.

I’ve discussed this previously: Velocity is great, but mass penetrates. In that post, I used the example of a whiffle-ball versus a baseball, where they both had the same “ME”, but where you’d feel a significant difference if you were hit by both.

And I think that the same thing is happening here. For what it’s worth, you’d need to push the 4 Bore ball to about 800 fps to get it to the same nominal ME as a 12 gauge shotgun slug. To get to *triple* the ME of a 12 gauge shotgun slug, you’d need to push the 4 Bore ball to about 1400 fps. My guess is that the historical 500gr load of black powder might accomplish that.

But I sure as hell wouldn’t want to shoot it.

Oh, and how accurate was the 4 Bore? Here’s our target from the full-power loads:

Not bad for no sights, at about 15 yards. And look at the size of those holes!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

OK, let’s talk about the other gun in the pic at the top. It’s a Hand Mortar, designed to throw a small hand grenade further than the human arm could. We had this one just for a little fun, shooting tennis balls about 100 yards using 70gr of Fg black powder. Like this:

Here’s a slow motion version of my friend Tim shooting it:

And here’s another of my friend Charles:

Black powder is so much fun!

Jim Downey

May 19, 2021 - Posted by | Anecdotes, black powder, Data, Discussion., General Procedures, Shotgun ballistics | , , , , , , , , , , , , , , ,

1 Comment »

  1. […] [The entire post can be found here.] […]

    Pingback by Shooting big stuff. | Communion Of Dreams | May 19, 2021 | Reply


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