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Bore Diameter Variations

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concretus
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Bore Diameter Variations

#1 Post by concretus » Thu Nov 02, 2017 11:29 am

Hello,
I have an 1898 model with a cartouche stamp of 1901. When I started to reload for it I came to the conclusion .308 bullets were inaccurate and inconsistent. I slugged the bore and determined it to be .310. I switched to .311 bullets and now shoot minute of angle...My question is was that common for the bore size to vary between rifles??? I guess with the lead bullets used for the .30 Army it could or is that just an assumption??? Thanks

les1234
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Re: Bore Diameter Variations

#2 Post by les1234 » Thu Nov 02, 2017 11:01 pm

Mine needs a .310 bullet when shooting cast, variations in bore sizes is pretty common with them. The Army never used lead bullets in the Krag, the original bullet was a long , heavy, round nose jacketed bullet, I believe 220 gr. But the bullets had an open base, not solid jacketed at the base like modern hunting type bullets, so upon firing, the base of the bullet could actually expand or to seal the bore.

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Re: Bore Diameter Variations

#3 Post by DaleH » Fri Nov 03, 2017 12:29 pm

Most Krags are ‘overbore’ to the typical 308 and I was just at a shoot last weekendwhere there were
more than a few Krags present, along w/even more Krag aficionados ...and yet I’ll dammed if I can remember why ...

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Re: Bore Diameter Variations

#4 Post by DaleH » Fri Nov 03, 2017 12:34 pm

Found this posted on the milsurps forum, by ‘Plain Old Dave’ in 2010 ... not sure I can post the full
link here. Moderators?

“Bore diameter. Between the erosive powders and early technology (indifferent barrel steels and no gauging to ensure uniformity of bore diameter), Krag bores can vary considerably in diameter. In the mid 1930s, Phil Sharpe had documented Krag bores as tight as .3075 and as open as .3125. With 60+ more years of bore wear, even with modern non-corrosive priming and modern non-erosive powders you may see even more bore diameter variation. Slug your bore and you may be surprised to discover your .30-40 Krag that won't hit the broad side of a barn is a STUNNINGLY accurate .303-40 Krag.”

concretus
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Re: Bore Diameter Variations

#5 Post by concretus » Fri Nov 03, 2017 1:06 pm

Thank you for your responses.....

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Re: Bore Diameter Variations

#6 Post by slowbob2 » Sun Nov 05, 2017 2:15 pm

All early military rifles were made with varying GROOVE diameters , The bore dia were always close . They were bore riding the bullets and did not care about groove dia . The grooves do not wear , the lands will wear first and more . Just like tires , the grooves in them do not get deeper . All military of that time used bullets smaller tham the groove dia .

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Re: Bore Diameter Variations

#7 Post by garra » Sun Nov 12, 2017 2:15 pm

I have 2 Krags a carbine and a long rifle with different bores. the carbine is a 1894 bore .304/.312, the rifle an 1898 bore .300/.310. these figures are from the bore casting.

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