Question: How to measure in order to duplicate best possible ammo?

Question: How to measure in order to duplicate best possible ammo?

This is a discussion on Question: How to measure in order to duplicate best possible ammo? within the Reloading forums, part of the Defensive Ammunition & Ballistics category; I assume that for a given caliber and gun, there is a perfect size and shape to the feed ramp, throat and chamber, as well ...

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Thread: Question: How to measure in order to duplicate best possible ammo?

  1. #1
    VIP Member Array ccw9mm's Avatar
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    Jul 2006

    Question Question: How to measure in order to duplicate best possible ammo?

    I assume that for a given caliber and gun, there is a perfect size and shape to the feed ramp, throat and chamber, as well as the bullet's overall length and crimp, that will allow for perfect feeding. And let's assume that, once found, someone wants to duplicate the setup in another instance of the same make/model of gun and cartridges.

    My question is: What is the best collection of measuring tools that can help guarantee that the "perfect" ramp/throat/chamber shape as well as the "perfect" bullet (once found) can be readily duplicated?

    What measuring/cutting tools for the gun, once acquiring a second one and needing to make adjustments?

    And, what measuring tools for the cartridges, once setting up a reloading station to duplicate them?
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  2. #2
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    You're asking some very good design-type questions.

    If you confine the discussion to one particular gun and caliber then I think you would have to know what the design dimensions are, as well as the design tolerances. I'd be less concerned with the feed ramp, since that's a non-moving part. The alignment of the barrel to the slide and frame (assuming a 1911-like design, not a "fully supported" barrel with integral feed ramp) would be of concern; this is governed by the slide stop in most current designs so the location and diameter of the slide stop are contributors as well. The biggest variable, though, would be how the magazine registers in the frame. The cutout on the mag for the mag catch on the frame has to be held to a tight tolerance, and the closeness of the magazine fit over its length will control the gross angle at which the top cartridge is going to approach the feed ramp. Lastly, the feed lips, magazine follower, cartridge length and bullet geometry all affect the path of the round into the chamber.

    I don't think you can make few simple measurements on a gun in your hand to see how well it meets the ideal set of dimensions. If you examined the gun's design, you could probably identify a dozen or two dimensions which are critical "drivers" of the ideal geometry you'd like to emulate. Realistically, a Coordinate Measuring Machine (CMM) is the ideal tool because it can measure linearly in 3 axes and usually two axes of rotation (curves). Before we had CMMs we used plug gages, micrometers, height gages and a LOT of trigonometry.

    I'm guessing that probably wasn't the answer you were hoping for.

    For the ammo, it should be a lot easier. If you confine yourself to a specific bullet type with its characteristic ogive, then seat that bullet to a specific depth in a case of known overall length, you should be able to check that with a go/no-go gage, or even a profile gage that allows you to see light around dimensional gaps if the cartridge is undersized or rejects it altogether if oversized. (sorry for the run-on sentence).
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  3. #3
    Distinguished Member Array razor02097's Avatar
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    Oct 2009
    Most times I reload according to a book's specifications. I am not entirely sure what you are trying to accomplish. Accuracy? Reliability? Other?

    Really a good caliper, case trimmer and dies are a wonderful place to start. Selecting a good bullet is really trial and error. Some guns like certain bullets and some don't care.

    Bench rest shooters get molds of their rifle's chamber to blueprint the dimensions of it. They also use once fired brass and just neck size it because it would be fire formed to their rifle. There are also kits that allow you to press a molding piece down the barrel to measure dimensions of the barrel twist and rifling. blue printing a rifle isn't cheap but it can be done. For pistol I guess you could just send them the barrel since the feed ramp, chamber, breech and barrel are 1 piece.
    There is something about firing 4,200 thirty millimeter rounds/min that makes me feel all warm and fuzzy inside.

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