"Ballistics by the inch" - free new resource.

[Shadan7]

Hey everyone, just wanted to post the 'official announcement' here about the launch of a new ballistics research project website: Ballistics by the inch. From our hompage:

Why "ballistics by the inch"? Well, just about forever people have wondered what kind of trade-off one made in choosing a gun with a short barrel - how much power were you giving up for convenience/concealability? There has been a lot of anecdotal information available - comparing this 2" .38 to that 6" .38, or a longslide .45 to an officer’s pistol with a shorter barrel - but there hasn’t been much in the way of consistent research made available to the average gun owner. In the 1980s American Rifleman did some tests using a .44 mag revolver, cutting the barrel down from 18" to 1", and back in the 1930s someone did something similar with a 30-30. But just try and find that data quickly. And further, how does that data compare to your 9mm or .32? Do they all lose power at the same rate? Are some ammos better for your purpose than others?

We were curious just exactly what the drop-off in velocity was for a given caliber over a range of barrel lengths, and using a variety of available ammunition. So, we decided to do some actual testing. And, we wanted to make this information freely available as a service to gun owners everywhere. This website is the result.​

The site has full documentation of the project (over 6,000 rounds fired), easy to see summation tables for the results, clickable graphs showing the curve of each ammo over the 18" - 2" barrel lengths, an associated blog, and a lot more. You can download the entire database for your own use as well. Stop by, check it out, spread the word to others who may be interested.

Jim Downey

(Mods - if you think this would be better in a different forum, please feel free to move it.)

 

[capbuster]

Thankyou for the most interesting site. take care.

 

[Marcus L.]

The only problem is that most auto pistols and pistol caliber carbines are recoil operated. So, by the time the bullet reaches the muzzle of a 16" barrel the beginning stages of ejection are occuring and some gas escapes in the action reducing velocity. Most pistol caliber carbines only give you a velocity gain of 100fps maximum. You get the same level of velocity loss in using a gas operated system. Unless you are wanting to use a single shot hunting rig, those Thomson numbers do not translate into a pistol or pistol carbine velocities. With a single shot locking breech and full chamber support you get virtually no back pressure.

In semiautos there is a threshold of barrel length to back pressure ratio and you run into the law of diminishing returns as you increase barrel length.

 

[Shadan7]

That's why...

...we have "real world" guns for each of the calibers tested, using the same ammo in a head-to-head comparison, with those results listed and incorporated in the graphs for each ammo. You can see exactly how they compare and draw your own conclusions from there.

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[JImbothefiveth]

This would be good for the "THR library".

 

[Marcus L.]

Shadan7,

I see an average of one firearm per caliber with usually a single barrel length. There are some major discrepancies in some of them in comparison to the Contender velocities. Real world firearms have real world back pressure.

Don't get me wrong, it's interesting, but it doesn't help the average real world person looking for real world velocities in real world firearms. Most notably those who think that they would be gaining a big advantage in using a pistol carbine over a pistol when they should be thinking shotgun or rifle. Virtually all pistol caliber semiauto carbines only give a 50-100fps velocity increase over a standard pistol.

 

[Shadan7]

Marcus,

You're right, we only tested one or two real world pistols per caliber. But that is all real data - you're welcome to download either the .pdf or the Excel version of the actual data to examine. In fact, we hope that people will use this as a starting point - anyone who wants to test actual pistol caliber carbines and post the information on the blog (or, if it is systematic and carefully done, we will post it on the site itself). The project was primarily concerned with typical pistol-length barrels; we started at 18" as a standard length only.

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[grendelbane]

Virtually all pistol caliber semiauto carbines only give a 50-100fps velocity increase over a standard pistol.

This has not been my experience. My experience is that a 16" AR15 9mm carbine will usually increase velocity by 100 to 200 FPS, and that a .45ACP AR15 carbine will usually increase velocity by 75 to 150 FPS.

Now, 50 FPS between otherwise identical guns of the same barrel length is not unheard of. Some are fast, and some are slow. Perhaps, everything I have clocked was slow for a pistol, and fast for a carbine, whereas your experience was with fast pistols and slow carbines.

The weight of the bolt in a blowback action should indeed influence the velocity. I think this is why velocities I see reported for the Marlin Camp Carbine are lower than what my AR's produce. Lots of other variables to ponder, also.

Plenty of people tell me that my .45 carbine actually loses velocity, compared to a pistol. The chronograph tells a different story. Could some one find a pistol/carbine combination where the pistol is faster than the rifle? I suppose it is possible, but I haven't found one yet.

 

[SeanSw]

Wow, those heavy .45acp loads don't care much for longer barrels. I expected 9mm to follow this trend by maximizing itself early but it does pick up a fair amount of velocity.

 

[RyanM]

The only problem is that most auto pistols and pistol caliber carbines are recoil operated. So, by the time the bullet reaches the muzzle of a 16" barrel the beginning stages of ejection are occuring and some gas escapes in the action reducing velocity.

Actually, most of the time the heavy barrel prevents the gun from cycling all the way. This company in Austria makes 16" barrels for Glocks, and they need recoil-enhancing devices on them, like on silencers, to function properly.

 

[Shadan7]

SeanSw, I too was interested by the .45acp results. One thing that really impressed me was the CorBon 165 and 185gr JHP rounds - that's an impressive speed for a .45 - sized hunk of metal.

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[grendelbane]

The heavier bullets of the larger calibers will not gain as much of a velocity increase as the lighter bullets of the smaller calibers. This is because the energy increase is usually similar, but the heavier weight bullets don't have to go that much faster to enjoy the same energy increase.

Not that energy, velocity, or bullet weight tell the whole story.

 

[grendelbane]

The heavier bullets of the larger calibers will not gain as much of a velocity increase as the lighter bullets of the smaller calibers. This is because the energy increase is usually similar, but the heavier weight bullets don't have to go that much faster to enjoy the same energy increase.

Not that energy, velocity, or bullet weight tell the whole story.

 

[grendelbane]

The heavier bullets of the larger calibers will not gain as much of a velocity increase as the lighter bullets of the smaller calibers. This is because the energy increase is usually similar, but the heavier weight bullets don't have to go that much faster to enjoy the same energy increase.

Not that energy, velocity, or bullet weight tell the whole story.

 

[grendelbane]

The heavier bullets of the larger calibers will not gain as much of a velocity increase as the lighter bullets of the smaller calibers. This is because the energy increase is usually similar, but the heavier weight bullets don't have to go that much faster to enjoy the same energy increase.

Not that energy, velocity, or bullet weight tell the whole story.

 

[TeamCorbon]

Great job! Lots of good info here. We will be using it as a resource for sure.

Thanks!

 

[Shadan7]

TeamCorbon -

Michael, you might pass the word along that adopting a similar set of protocols to test your own ammunition and then releasing the data would probably give your company a real edge in the market. We undertook this project because there is no easily comparable standard between brands. The company that first adopted such protocols and was transparent with their results would have the jump on the competition.

Just a thought.

Jim D.

 

[BullpupBen]

Great site! I've looked hard for comprehensive tests just like these to no avail

By the way, it would make it easier to read if you listed the barrel lengths of the test guns so we can see how it matches with predicted results.

 

[chriske]

Great initiative ! Real-world hands on tests & useful results, available free
You're to be thanked & congratulated.

 

[TeamCorbon]

TeamCorbon -

--------------------------------------------------------------------------------

Michael, you might pass the word along that adopting a similar set of protocols to test your own ammunition and then releasing the data would probably give your company a real edge in the market. We undertook this project because there is no easily comparable standard between brands. The company that first adopted such protocols and was transparent with their results would have the jump on the competition.

Just a thought.

Jim D.
__________________
Ballistics by the inch: "Three guys, two chronographs, and 7,000 rounds of ammo."

Like Science Fiction? Read *or listen to* my novel, Communion of Dreams, for free.

Jim,

We don't post much in a way of results from any of our testing. It is much better coming from an independent source. When people read results from a company's testing, they take the info with a grain of salt and often doubt the results because some companies will skew the results in their favor.

Thanks,

 

[max popenker]

Shadan7, that's a great job, well done!

Now, if only we can hope for the similar resource about rifle ammo (say, in barrel lengths from 16" to 30")...

PS yes, something like "from 10"" would be more interesting, but i know NFA limitations, and do not want to ask anyone to get into troubles with Boys Against The Firearms

 

[Floppy_D]

Great site, I enjoy reading over there. Thanks!

 

[Shadan7]

BB, yeah, we've debated that. But with the link to the list of "real world" pistols, as well as plotting their performance on the pop-up graphs (you can click any listed ammo at the top to get the graph), didn't think it was too much of a problem. But we may tweak that - remember, all this just went live this weekend.

Michael, fair point.

Max, that was the reason we went with the T/C Encore as the base platform - so there was no question about us having "illegal" rifles. That kind of grief we don't need. But yeah, if someone were to do such a project in the future, going down to only 16" would be useful but unfortunately limited.

Everyone else, thanks for the kudos and feedback. We had over a thousand visitors over the weekend, something like 7,500 page views. Help to spread the word - we want this resource used. Oh, and be sure to check out the companion blog!

Jim D.

 

[Shadan7]

Update on "Ballistics by the inch"

Just a bit of update, and some news...

We're over 200,000 hits on the site in less than two weeks. Over 700 people have downloaded the full data spreadsheets so far.

And after seeing the response so far, and kicking around the idea, we've decided to do some additional testing next spring and post that information along with the rest. The next round of testing will be for the .327 Federal Magnum, the .41 magnum, and the 10mm. Sorry for the wait, but there is some lead time in getting the barrels made and adding the project into our schedules.

Cheers everyone!

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[Jason M]

The only problem is that most auto pistols and pistol caliber carbines are recoil operated.

What gun they used is irrelevant. 800fps from a locked breech or from a blow-back operated pistol is still 800 fps. It still provides a comparison of energies between calibers and numerous velocities, if anything.

Jason