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


barrel length Federal Premium, .357 magnum, 158 gr. Hydra-Shok JHP
.006" cylinder gap .001" cylinder gap no cylinder gap
18" 1449 1490 1492
17" 1387 1406 1451
16" 1354 1394 1444
15" 1368 1394 1469
14" 1353 1410 1450
13" 1349 1396 1444
12" 1327 1378 1428
11" 1310 1357 1415
10" 1301 1352 1408
9" 1286 1342 1403
8" 1302 1343 1389
7" 1297 1321 1371
6" 1290 1304 1359
5" 1265 1255 1328
4" 1211 1224 1282
3" 1197 1215 1233
2" 1096 1134 1148

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.