BBTI testing the effect of revolver cylinder gap

Steve Johnson
by Steve Johnson

I was excited to hear from Jim that Ballistics By The Inch will soon be testing how much a revolvers’ cylinder gap effects the ballistic performance of a round.

We’ve had a Single Action Army clone in .357 magnum modified to allow for adjusting the barrel position from a standard 0.006″ to 0.001″ to no gap (barrel snug against the cylinder). We have a dozen or so different ammunition loads in .38/.357, and we’ll be essentially repeating the BBTI procedure for each of these, with the normal gap then the minimum gap then without any gap, starting with an 18″ barrel and going down in increments of one inch to just 1″ . Actually, one slight difference – to make sure we get a better statistical sample, we’ll be firing 10 (ten) rounds of each type of ammunition at each point rather than just 3 (three) as we did with the BBTI tests. Because we are limiting this test to just one caliber, we thought this was a reasonable step to take. We hope that this will allow us to conclude with some actual data what the effect of having a cylinder gap in a revolver actually amounts to.

These tests are sure to settle a few arguments.

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Jim D. Jim D. on Dec 01, 2009

    Hi guys,

    One advantage of the way we're doing this (not spelled out in the original post, so there's no way you'd know) is the way we're setting up to do the tests. We'll be using some spacer rings worked up by our gunsmith (who did a right fine job with our custom barrels for the T/C Encore in the original tests) so that we get very consistent and quick spacing on the cylinder gap. Controlling this variable means better data with all the test shots fired.

    Freiheit, you're welcome - while between us we've got a lot of skills, none of us pretends to be talented in either statistics or data crunching. Making the raw data available has meant that we don't need to be - those who are can do the work! Call it "crowdsourcing", and everyone wins. ;)

    Cheers -

    Jim D.

  • Raoul O'Shaughnessy Raoul O'Shaughnessy on Mar 19, 2012

    "We’ve had a Single Action Army clone in .357 magnum modified to allow for adjusting the barrel position ...."

    They couldn't find a used Dan Wesson anywhere and save themselves a few bucks?

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