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20 Bore


wymberley
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On an impulse which I couldn't resist I have somewhat belatedly become an owner of the Subject calibre of Italian extraction. Stamped on both barrels is 16 which in English is 0.630". I don't have a bore scope and using a telescopic gauge and micrometer that is the dimension I get - ish. Step-son took a liking to it so have managed to find one for him having the identical spec - lucky as we're talking fixed chokes 26" barrels and double triggers and straight hand stocks and even the same year. There is just a minor difference in choking. I have just bought this remotely and am uncertain about some information given. Not too sure whether the 15.9 quoted is stamped or whether this is simply the metric equivalent of the 0.626 and 0.627" figures also supplied. I'm not too fussed and can wait until I get it to find out

Question: (Although I'm not at all concerned, but ask simply out of interest.)

Burrard gives a 20 bore barrel diameter as 0.615". An American source (Remington) gives the old European standard as as per Burrard and the new European as 0.619". So, is the Italian and specifically Beretta spec' different? The guns are S56E from '77.

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Old British 20 bore nominal size was .615" .Continental sizes tended to be .622"/.626". For 20 bore the actual bore size range was between .610" and .630" or 15.5mm and 16mm.

After metric sizes were introduced in 19185 the nominal British bore size was .614"/15.6mm but may were actually bored to .618"/15.7mm or .622"/15.8mm due to many using continental sourced tubes . 

I dont quite understand the " 16 " as I would have thought this was the nominal bore which would have been.661"/16.6mm. Again continental guns tended to be 16.9mm /.665"[16 bore range 16.7mm and 17.4mm

Without being able to see and measure it is hard to say other than to ask are you sure it is a 20 and not a 16 bore ?

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17 minutes ago, Gunman said:

Old British 20 bore nominal size was .615" .Continental sizes tended to be .622"/.626". For 20 bore the actual bore size range was between .610" and .630" or 15.5mm and 16mm.

After metric sizes were introduced in 19185 the nominal British bore size was .614"/15.6mm but may were actually bored to .618"/15.7mm or .622"/15.8mm due to many using continental sourced tubes . 

I dont quite understand the " 16 " as I would have thought this was the nominal bore which would have been.661"/16.6mm. Again continental guns tended to be 16.9mm /.665"[16 bore range 16.7mm and 17.4mm

Without being able to see and measure it is hard to say other than to ask are you sure it is a 20 and not a 16 bore ?

Many thanks. The "16" is not too clearly stamped in either case but does equate to my (ish with the tools at hand) 0.630" and is definitely a 20 bore. The choking is stamped 2 and 4 small circles (not stars) which I figure is 1/4 by 3/4, but I measure it as 1/2 by Full. The second gun will have to wait until I get it but looks like having a tad smaller bore.

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Choking is not always directly translatable between continental makers and what we except as standard .

Spanish tended to between set limits for each choke size and tended to be on the tight side  , Belgian worked in steps of .2mm [.008"] for example .Italians seemed to vary from maker to maker .

 

 

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