Why do they call it 28mm

Discuss 5.7x28mm factory ammunition
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celtic88
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Posts: 4
Joined: 16 Jan 2017, 07:29

Why do they call it 28mm

Post by celtic88 » 19 Jan 2017, 00:31

Anyone know which projectile is 28mm?
Of the 6 or 7 different bullets I have range from 13mm to 20mm
I did a little bit of looking earlier and 20mm is as long as I can find.
My 7.62x39's are 39mm long and my 7.62x51 are 51mm long,
Why are the 5.7x28 not 28mm long?
Not that it really matters though

DoubleJ
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Posts: 400
Joined: 10 May 2011, 20:20

Re: Why do they call it 28mm

Post by DoubleJ » 19 Jan 2017, 04:52

It's the case length...but not exactly.

celtic88
Junior Member
Posts: 4
Joined: 16 Jan 2017, 07:29

Re: Why do they call it 28mm

Post by celtic88 » 19 Jan 2017, 09:15

Yeah definitely not exactly. 28mm is 1.105in
I get 1.137 on fnh brass and 1.135 on ae brass.
But I guess that's splitting hairs talking hundredths of an inch.

DoubleJ
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Posts: 400
Joined: 10 May 2011, 20:20

Re: Why do they call it 28mm

Post by DoubleJ » 19 Jan 2017, 17:10

Yup, welcome to FN world, where no one else lives. It's also not a .224 bore, saw one slugged recently at .221. I measured a fired case, came up with 29.xx mm without trimming, but no way am I knocking a mm off during trimming, so it's all make believe, just like the .38 and .380.

Grocerius Maximus
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Joined: 26 Jan 2012, 05:56

Re: Why do they call it 28mm

Post by Grocerius Maximus » 16 Mar 2017, 15:52

.224" (5.7mm) is NOT the bore size, its the nominal bullet diameter. In 22 centerfire nominal bore diameter will be .005"-.006" under bullet diameter depending on rifling geometry, .218"-.219".

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