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Thread: Info on TK Custom 9mm conversion

  1. #31
    Member Rock185's Avatar
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    Bill, Can't say I blame you, 38 wadcutters are more pleasant to shoot than 9mm in the little revolvers. I'm not tough, but I think different guns and calibers beat people up differently. Some guns that others enjoy, are not fun for me My 3" SP101 is more pleasant to shoot than the lighter S&W 940, but 38 wadcutters are more pleasant yet.
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  2. #32
    I agree. When I want to minimise recoil, I stick the original heavier stainless cylinder back in my 637 and shoot wadcutters. 9mm is mostly for carry.

    BTW, re barrel length and ballistics, my Micro 9 has a 3.15" barrel length, which they measure from the primer forward to the end of the barrel. My 1-7/8" barrel J-frame measured from the same two locations, is 3.50".

    I think perhaps this measurement disparity may sometimes lead to some questionable chronograph conclusions regarding bullet weight, barrel length, velocity, and energy.
    Last edited by JimCunn; 02-16-2019 at 09:17 AM.

  3. #33
    Member Rock185's Avatar
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    JimC, Yep, we can add cylinder length to revolver barrel length in the equation if desired, but the chronograph doesn't care. Still interesting to me that revolvers releasing all that high pressure gas at the B/C gap, routinely produce the velocities that they do in comparison to semi autos. For instance, looking through some of my notes I see I chronographed the popular Federal 9mm 124+P HST in a semi-auto with 3.5" barrel, and a 2" revolver that measures almost 3.5" breech face to muzzle. The 3.5" semi-auto produced 1166 FPS, the revolver 1195 FPS. The same ammo in a 3" revolver, that probably measures about 4.5" if we include cylinder length, produced 1291 FPS, a 5" semi-auto 1236 FPS. Obviously, I don't have unlimited types and barrel lengths to test, but I've chronographed a fair amount of 9 and 10mm in revolvers and semi-autos, and results like this are not unusual. All ballistically interesting and good clean fun to me
    Last edited by Rock185; 02-16-2019 at 02:22 PM.

  4. #34
    "but the chronograph doesn't care".

    Agreed, but easy to miscompile and misinterpret in the written summaries, tabulations, and conclusions.

    Fluid mechanics is what I do professionally. I'm not surprised that the cylinder gap doesn't cause significant losses, though I've never bothered to attempt to quantify it (I'm lazy by nature).

    I'd actually expect the revolver velocities to be slightly greater because of the momentum that gets transferred to the slide in the semi-autos.

    What''s your opinion of the ProChrono DLX chronograph? (about $135 from Brownells).
    Last edited by JimCunn; 02-16-2019 at 06:01 PM.

  5. #35
    Member Rock185's Avatar
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    I have used two PACTs, a friend's Oehler, another way older type belonging to an acquaintance, but not a ProChrono. Knowing me, I'd probably get around to shooting the downrange electronics in the ProChrono brfore it was over with, and I don't have a Smart Phone for it to talk to anyway Now days, I think about any of the commonly available chronographs will do the job. Several years ago, we arranged the PACT and Oehler in tandem. The difference in velocities recorded was insignificant. I doubt the results would be much different using other manufactuer's products...

    BTW, I think you may be on to something there about the momentum transferred to the slide. Many years ago, before I'd ever even seen a chronograph, an acquaintance was sure that revolvers were more powerful than autos because of that very thing.
    Last edited by Rock185; 02-17-2019 at 01:36 AM.

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