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Bullet Sizes

leadburnerleadburner Member Posts: 81 ✭✭
edited June 2007 in Perry Shooter Competition Shooting and Reloading Forum
I've been reloading for 25 years and casting for 20 and I just learned something.I've never measured component bullets before and was measuring some I found stashed away.These were some I had pulled years ago and I couldn't remember what they all were from.The .30 cals. measured .305 instead of .308,the 7mm's were .282,not .284.I then went to my bullet cabinet and measured a couple from several new boxes,including .224's(measured.223),6mm's(.243),7mm's(again.282),and .30's(again .305).My cast bullets for all calibers measure what I sized them at.I guess my question is has this always been the case(undersized bullets)or is it something fairly recent.I suppose it would help keep our pressures down,but it would seem to me that it would affect accuracy in all but the tightest bores.Have I just really missed something here?
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    jonkjonk Member Posts: 10,121
    edited November -1
    Well dunno what you've found, but I've checked mine and they generally measure as they should...

    Undersized bullets aren't the end of the world; common thought when jacketed bullets were introduced was to be a few thousandths under bore diameter- so the bullet would 'upset' into the rifling. This works better with deep cut rifling than with shallow. So they MAY shoot fine, esp. with a fast powder. Neck tension might be an issue. But you do have an element against you, trying to develop an accurate load with jacketed bullets more than 1/1000 under bore diameter, and a leaded mess if you try it with cast unless dead soft.
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    bpostbpost Member Posts: 32,664 ✭✭✭✭
    edited November -1
    Me thinks you need to get your measuring device calibrated; it might need adjustment. [:I]
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    leadburnerleadburner Member Posts: 81 ✭✭
    edited November -1
    Well,that is a possibility,it is just an RCBS dial caliper!
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    Tailgunner1954Tailgunner1954 Member Posts: 7,734 ✭✭
    edited November -1
    Measure enough factory and military cartridges, I've done a bunch, and you'll find that it's not at all uncommon for them to vary by more than your seeing.
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    Hawk CarseHawk Carse Member Posts: 4,369 ✭✭✭
    edited November -1
    quote:Originally posted by leadburner
    Well,that is a possibility,it is just an RCBS dial caliper!


    I have one of those, made in Communist China. Good enough for case length and cartridge OAL, but when I want to measure something precisely, I get out my good old US Starrett micrometer.

    Wasn't too likely they were ALL undersize.
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    HandLoadHandLoad Member Posts: 15,998 ✭
    edited November -1
    I'm with HAWK and BPost - you probably dropped your caliper, or have never checked it on a gage block. It must be out of calibration.

    Close it up all the way - does it say 0.000?
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    leadburnerleadburner Member Posts: 81 ✭✭
    edited November -1
    Yes,it does zero out,and it measures my cast bullets at what I sized them at,30's at .309,7mm's at.285,6mm,s at.244,22's at.224,etc.I'll have to look into this further.[?][?][?]
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