0.604 inches http://www.wildfowlmag.com/tips_strategies/shotgun_062304/
.020
You can pretty much bet on full or modified, but the actual determination of choke is made by comparison the inside diameter of the muzzle to the inside diameter of the barrel before the bore. sales@countrygunsmith.net
bore diameter
The measure related to the diameter of the bore and the size of the shotgun shell is known as "gauge." The gauge is determined by the number of lead balls of the bore diameter that equal one pound; for example, a 12-gauge shotgun has a bore diameter that allows for 12 lead balls of that diameter to weigh one pound. The smaller the gauge number, the larger the bore size. This system is commonly used to classify shotguns and their corresponding ammunition.
'*' designates full choke (F). '*-' designates improved modified choke (IM). '**' designates modified choke (M). '**-' designates improved cylinder choke (IC). '**$' designates skeet (SK). '***' designates cylinder bore (CYL).
'*' designates full choke (F). '*-' designates improved modified choke (IM). '**' designates modified choke (M). '**-' designates improved cylinder choke (IC). '**$' designates skeet (SK). '***' designates cylinder bore (CYL).
25-100 usd
'*' designates full choke (F). '*-' designates improved modified choke (IM). '**' designates modified choke (M). '**-' designates improved cylinder choke (IC). '**$' designates skeet (SK). '***' designates cylinder bore (CYL).
'*' designates full choke (F). '*-' designates improved modified choke (IM). '**' designates modified choke (M). '**-' designates improved cylinder choke (IC). '**$' designates skeet (SK). '***' designates cylinder bore (CYL).
Generally the nominal diameter of cylinder bore is kept little smaller at cylinder head than at the bottom. The engine head will be generally heat and it tends to expand for these high temperatures. To prevent the bore diameter at head to exceed diameter at bottom,piston engine bore is ground with a slight choke.
A shotguns gauge is a measure related to the diameter of the smooth shotgun bore and the size of the shotshell designed for that bore. Gauge or diameter of the bore is determined by the diameter of 1 lead pellet times the number of pellets required to equal 1 pound. ex. 12 gauge is equal to the diameter of 1 of the 12 lead balls that equals 1 pound. ex. 20 gauge is equal to the diameter of 1 of 20 lead balls that equals 1 pound. ex. 3 gauge is equal to the diameter of 1 of the 3 lead balls that equals one pound. The larger number of gauge the smaller the bore.
'*' designates full choke (F). '*-' designates improved modified choke (IM). '**' designates modified choke (M). '**-' designates improved cylinder choke (IC). '**$' designates skeet (SK). '***' designates cylinder bore (CYL).