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O.A.L. Query |
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Strangely Brown 
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Joined: April 05 2022 Location: Wiltshire Status: Offline Points: 187 |
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 Topic: O.A.L. QueryPosted: January 20 2023 at 7:54am |
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I have an O.A.L. question regarding Sierra MK's, or rather to save any misunderstandings a C.B.T.O. (Case Base To Ogive) query. Do any of you remeasure C.B.T.O. for every batch of bullets you get or just hope there're all the same measurement? I've just acquired 4 boxes of .311 174gr SMK's and the packaging suggests 2 boxes are of earlier manufacture, there's an average of ten thou difference between them and newer ones. |
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Mick
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Goosic
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Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 7696 |
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Posted: January 20 2023 at 8:05am |
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Geoff might certainly have an answer for you regarding your question but, that particular question does sound like it lays within the boundaries of a BR shooter IMHO...
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Strangely Brown
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Joined: April 05 2022 Location: Wiltshire Status: Offline Points: 187 |
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Posted: January 20 2023 at 8:22am |
I blame my new Hornady O.A.L. gauge!
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Mick
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Goosic
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Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 7696 |
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Posted: January 20 2023 at 8:57am |
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I have that case gauge too.
The issue I was initially having was not realizing I was trying to get the same numbers using two different types of bullets. That being the Tangent and Secant ogives. The Tangent ogives in my 7.62mm No4Mk1* when set to an averaged OAL of 2.830" imitate the military M852 Match Round pretty much dead on. Using Hornady 150grn bullets with the Secant ogives in my 303B produced less than desirable results until I seated them out beyond normal conditions which left me with the firm belief to just keep using the 174grn BTHP/FMJBT Tangent bullets seated to an OAL of 3.035" Set It And Forget It!!...
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Shamu
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Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 15960 |
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Posted: January 20 2023 at 12:10pm |
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I do, but by inference only. The original setup I used was worked out measuring with the OAL gauge, but then I measured COAL, creating an "offset". I have "master cases" for all my loads & check the seating die with those by simply backing off the micrometer stem, inserting a case & raising the ram. Then screw the seating die stem to a "firm contact". Then I seat a couple of "real" rounds & fine tune if needed. The results seem to tell me I'm doing something right!
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Goosic wrote: