450B case trim length: Contradiction & Confusion

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Re: 450B case trim length: Contradiction & Confusion

Postby Texas Sheepdawg » Mon Jan 29, 2018 9:43 am

Hoot wrote:
Draino wrote:...snip... I dont know where to measure at the web area to get a correct err....whats it called, 'case head expansion?' measurement, but at the lowest point before the extractor groove, IIRC it was .503-.505 I think. I will check again though.

Can


Set your micrometer to say .5000 and slide the resized, clean case through from front to rear. If it has been shot at least once, it will drag or catch where the widest spot is and that's usually right where the web transitions to the wall. That's the area of interest. Once that area exceeds .5015 or so, you run the risk of it seizing or dragging and preventing an AR bolt from rotating into battery, depending upon how tight, or not, your chamber is. If it fails to pass at .5015, it's scrap brass. Bolt actions in theory (see sig), will be more tolerant as you can cam the round into battery with more closing effort. Best to find out which cases are going to be problem children before you load them back up. Again, this is more of an issue in an autoloader. My clean chamber seizes cases at .5017, so not wanting to have issues at the shooting bench, I toss any case when it can't pass through the micrometer when set to .5015, to allow for soot fouling after an extended shooting session.

I grade my resized, clean cases into different peanut butter jars at .5000, .5005, .5010 and .5015. When choosing which ones to reload for a project, I usually use the .5015 ones for foulers and the .5005-.5010 for keepers. The .5000 are saved for hunting rounds, where I don't want anything to go wrong.

Hoot

Sorry to say this but IMHO, measuring this dimension is a job for a micrometer, not a caliper.


Hey Hoot, could you do me/us a favor and show us a picture of your micrometer and a link to where we could order one?
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Re: 450B case trim length: Contradiction & Confusion

Postby Hoot » Mon Jan 29, 2018 12:36 pm

Texas Sheepdawg wrote:...snip...
Hey Hoot, could you do me/us a favor and show us a picture of your micrometer and a link to where we could order one?


Mine (Brown & Sharpe brand) looks exactly like this one (borrowed image) but mine's in better shape.

Image

They're not expensive and if not abused, last forever. Mine is a 1960's unit that saw it's last calibration in 1995. You can get them for less than a box of 450b ammo on ebay. Look at the seller's reviews and number of transactions as a good indicator. Carbide tipped jaws are the best ones. My tips still have a mirror-like finish on them. Again, take care of them and they'll outlast you.

Hoot

EDIT: example from ebay: https://www.ebay.com/itm/VINTAGE-No-1-BROWN-SHARPE-599-1-MICROMETER-0-1-with-WOOD-BOX-/192439125852
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Re: 450B case trim length: Contradiction & Confusion

Postby Texas Sheepdawg » Mon Jan 29, 2018 9:02 pm

Thanks. I played with those in Mechanics school back in the old days but they belonged to the school. Just never got around to adding one to my collection of tools.
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Re: 450B case trim length: Contradiction & Confusion

Postby plant_one » Mon Jan 29, 2018 10:31 pm

ive got this set on my bench.

http://a.co/02doaFh


theyre not super fancy, but theve held true so far give or take 0.0001 on peice of known diamater bar stock i have around for calibration. i lucked out and my uncle verified it for me with is recently calibrated set at work, so i have a free gauge to check my relatively cheap tools against :)
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Re: 450B case trim length: Contradiction & Confusion

Postby Hoot » Tue Jan 30, 2018 5:55 am

plant_one wrote:ive got this set on my bench.

http://a.co/02doaFh


theyre not super fancy, but theve held true so far give or take 0.0001 on peice of known diamater bar stock i have around for calibration. i lucked out and my uncle verified it for me with is recently calibrated set at work, so i have a free gauge to check my relatively cheap tools against :)


There's super fancy and there's accurate. They're not always synonymous. Accurate holds trump in my book. I've looked hard at those digital mics since my eyes are not getting any younger. I've been waiting for someone to testify about them before I buy one. We bought some $50.00 no-name dial calipers for work recently from MSC for general shop use. The build quality looked good but if you zero the dials with the jaws closed, they're off by as much as .002 at one inch. Not confidence building. I have 3) $20.00 no-name digital calipers and they do not suffer from that much drift going from zero to 1 inch. Go figure. My Starret dial caliper at home does not drift going from zero to 1 inch, so there is something to "getting what you pay for". I still prefer my digital calipers for ease of use but have to keep the battery flipped around when not using them for a prolonged time. Otherwise, they will slowly drain down the battery, even when off. Given that the display wakes up when you simply move the jaws, Off is more like Asleep. IE still drawing a little current. I always keep some Energizer Silver Oxide batteries on hand as they tend to pick the worst times to die. Better life expectancy than the Alkaline ones. At least the display flashes when the battery is almost but not quite gone.

Does that digital mic you bought drain the battery when Off for a prolonged time?

Hoot
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