ATTENTION:  Effective Sept 1, 2020, the BBTI Project is in "Archive Status."  No further tests will be conducted, but we will maintain this site and data for the use of the firearms community.  Thank you.

Cylinder Gap Test

Note the aberrant data point for the 13" 0.001 gap - all the data collected for this point would be consistent with the next ammo in line (the Black Hills .357 magnum rounds).  We suspect that we just grabbed the wrong box of ammunition for this one point.

barrel length Black Hills, .38 long Colt, 158 gr. RNL
.006" cylinder gap .001" cylinder gap no cylinder gap
18" 661 654 697
17" 611 634 659
16" 568 616 653
15" 603 622 683
14" 589 621 689
13" 569 877 665
12" 570 595 666
11" 559 594 665
10" 567 600 656
9" 563 587 654
8" 560 592 647
7" 559 591 634
6" 556 562 624
5" 538 564 607
4" 523 545 597
3" 521 535 568
2" 494 509 523

Other Resources

BBTI is not the end-all of ballistics testing, just one more component available for the common good.  In addition to extensive discussion about ballistics to be found at many gun forums, here are some other great resources pertaining to ballistics testing you should check out.  (And if you would like to recommend a site to list here, please send an email.)
  • BrassFetcher:  excellent resource, with an emphasis on bullet performance in ballistic gelatin
  • The Box O' Truth:  testing ammo penetration through various barriers
  • Terminal Ballistics Research:  Specializes in the research of cartridge & projectile performance, using hard data gathered from 20 years of hunting game.


We'd like to personally and specifically thank Pat Childs at Fin & Feather in Iowa City, as he not only helped get most of our ammunition and other supplies, he was the brilliant gunsmith who worked with us to make this insane project much more practical.  Without his help all of this would have been much more difficult and perhaps impossible.  Anyone who uses our data owes him a debt of gratitude.

And thanks to our spouses, who were not just tolerant but enthusiastically supportive of this rather nutty project.


This project, and all of its results, is only our fault.  We (well, Jim K, mostly) paid for everything ourselves, and we did not receive any kind of sponsorship or remuneration from anyone.  We did all the work.  We used products we were either familiar with, or because they were what was available, and mentioning them by name does not constitute an endorsement of any kind.  Furthermore, the data is provided purely for entertainment purposes - to better facilitate arguments over what ammo or caliber or gun is "best."  How you use the data is entirely up to you.  And if you think you could do better, feel free to spend the money and do the work and publish your own results.  Or not.  Your choice.