Modified case from Fired Brass

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bangbangping
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Re: Modified case from Fired Brass

Post by bangbangping »

rlandry6 wrote:I settled on the RCBS Precision Mic.
...
Like everything else here, this will probably come back and bite me in the butt
While a bit expensive, the precision mic works very well to do what you're talking about. You shouldn't have any issues, and you don't have to worry about the accuracy of your caliper.

Just be sure to throw the bullet portion of the mic in the trash. The theory that you can measure bullet jump for your specific bullet with a "generic" bullet is flawed. On top of that the tool itself is a crappy design, and it's impossible to get a consistent measurement. On the positive side it will break quickly, making it much easier to throw away. :lol:

Something you may not have considered: The precision mic is sold as being cartridge specific, but the body and case portion are the same across cartridge families. Only the bullet portion (which you throw in the trash) is specific to each cartridge. For instance, the 30-06 mic can be used for 30-06, 25-06, 270 Win, etc.
rlandry6
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Re: Modified case from Fired Brass

Post by rlandry6 »

I thought about the bullet portion when I first looked at it. What was RCBS thinking that one dummy bullet would work for everything out there.
I'll have to look at it for a bit, but it seems that the bullet portion of the mic could be used as a gauge to look at seating and adjust seating depths of an alreadly loaded round as long as a good dimension was obtained using the Hornady length gauge or something comparable.
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Jbroberson21
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Re: Modified case from Fired Brass

Post by Jbroberson21 »

The Hornady modified case requires 2 cases be sent to them and 15 bucks. I just got off the phone with them to verify that all they do is drill and tap the case. There is no change made to the neck or shoulder of the case. I see that causing a minor accuracy issue in the length of the amount that you bump your shoulder back, but I don't guess 1 to 3 thousandths matters all that much since it's only a reference point that will be experimented from and can be obtained consistently even if not exactly correct.
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Flatliner
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Re: Modified case from Fired Brass

Post by Flatliner »

I confess that given my age and number of years shooting, I should probably be able to answer not ask this question, but: Once you have this information for a specific rifle, what do you do with it to produce the most accurate handloads? How far off the lands should the ideal round be? Can you run this test on an AR? If so, what procedure do you use to get the "feel"
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SwampDog_13
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Re: Modified case from Fired Brass

Post by SwampDog_13 »

Flatline

Just like everything else in reloading, every rifle has what it likes. These numbers can change over time as well.

I typically find my distance to the lands then then start my load work up .020" off the lands. Of course this is only possible with cartridge/bullet and rifle combos that allow you to get there. Then I'll run my ladder test for charge weights. Once I find a node I like then I'll start tinkering with seating depths just like charge weights. For example if I like xx.xx grains of powder I'll move the bullet in and out in .002" all the way to the lands and out to .040" or so and look for groups to tighten or open. Be careful though, chasing these things can cause you to burn through components at a pretty high rate but in the end you wind up with some real good stuff and a lighter wallet :mrgreen: .
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Flatliner
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Re: Modified case from Fired Brass

Post by Flatliner »

That was kind of what I figured must be the case. Chasing it is half the fun though, right...
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dellet
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Re: Modified case from Fired Brass

Post by dellet »

Flatliner wrote:That was kind of what I figured must be the case. Chasing it is half the fun though, right...
In cartridges like 300 Blackout where SAAMI max length is magazine length, and there are literally hundreds of available bullets, knowing when a bullet hits the lands becomes a safety issue.

145-150 Fmj bullets are a good example. Not all of those can be loaded to 2.26”.

I would guess over the years on this forum I have seen at least 10 if not 30 loads where people were having pressure problems long before max charges were reached because they were jamming the lands.

Early Noveske barrels were “Match chambers”. This meant they had short throats. Even some factory ammo jammed the lands.

Hornady made mistakes in the 9th edition that could have been life changing, if load data had been followed exactly.

If you are going to handload, knowing where the bullet hits the lands, really should not be negotiable.
300 Blackout, not just for sub-sonics.
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