Firearms – Barrels – Choke devices
Reexamination Certificate
1999-05-06
2001-09-18
Johnson, Stephen M. (Department: 3641)
Firearms
Barrels
Choke devices
C042S076010
Reexamination Certificate
active
06289620
ABSTRACT:
This invention refers to a smooth bore rifle barrel. The internal geometry of smooth bore rifle barrels is generally common to any rifle type or model, based also on the fact that there are specific international standards defining the shape, proportions and measurements to be provided, depending on the various sizes of a barrel.
In particular, very narrow tolerances are provided in the initial portion of the barrel or cartridge chamber, while a relatively broader excursion of sizes is allowed in the intermediate or bore area and in the muzzle area. Tradition, experience and cartridge loading systems have dictated the adoption, on the part of practically the entirety of arms producers, of a bore diameter for smooth bore rifles of a caliber 12, equal to 18, 4 mm.
In this regard, it should be mentioned at the outset that the values of the dimensions of various portions of a rifle barrel mentioned in this application are meant to refer to a rifle of caliber 12, however, the principle of this invention equally applies to rifles of caliber 20, considering the appropriate corrections in the absolute values of measurement.
It is obvious, however, that in terms of the ratio between the various parameters, the values mentioned in this application apply both to rifles of caliber 12 as well as 20.
The 18.4 mm diameter size of a caliber 12 rifle barrel bore allows an excellent ballistic performance, considering the relationship existing between cartridge pressure, shot exit speed and recoiling force on the user's shoulder.
The relevant international standards allow adopting as a bore diameter value any figure within a range of 18.2 to 18.9 mm.
The onset of ever lighter rifles and the use of heavy charges, combined with the prolonged rifle usage as occurring in sports events makes it necessary to reduce the recoiling force, so as to soften the strain on the user and make it less troublesome.
This condition is particularly important in competitive events, where the shooting stress and trouble could affect results.
By adopting an internal rifle bore diameter within the allowable upper limits, meaning between about 18.8 and 18.9 mm, the recoil is reduced as a result of lower gas compression; however, such a diameter size results in a loss of gunshot charge exit speed.
For this reason, a diameter value close to the lower limit, meaning 18.4 mm, has always conveniently been used in order to prevent a loss of efficiency in terms of the useful arresting power or traveling distance of the gunshot, and therefore of the barrel's shooting reach.
The terminal portion of a traditional barrel provides for a restriction to reduce the exit diameter of the barrel for the gunshot, depending on the desired width of the spreading angle.
The restrictions may be built into the barrels themselves (fixed restriction barrels) or they may be achieved by interchangeable chokes, applicable on a universal barrel size fitted with an appropriate seat in the muzzle area.
The starting diameter of the interchangeable chokes is directly dependent on the bore diameter; for a weapon with a bore diameter of 18, 4 mm, for example, the choke diameter equals 18.5 mm, so as to ensure a continuity inside the barrel, without introducing dangerous irregularities.
The foregoing description makes it evident that it would be desirable to produce barrels having a bore equal to the maximum allowable size, meaning of 18.8-18.9 mm, so as to achieve a softer recoiling action on the user's shoulders; on the other hand, however, this would result in a loss of the projectile's exit velocity and in the use of variable chokes, with respect to the traditional types for barrels with interchangeable chokes, of different inlet diameter and thickness.
This solution would therefore generate additional drawbacks, owing to the loss of interchangeability wit the traditional chokes.
Moreover, due to the greater thickness of the barrels, the reduced convergence between the two barrels of a superposed rifle (“double barrel rifle”) would cause some shot centering errors, in the sense that the first and the second shot would hardly be able to hit the target in the same manner.
The purpose of this invention is therefore to offer a smooth bore rifle barrel capable of eliminating the mentioned drawbacks, or to indicate a rifle barrel capable of achieving a reduced recoiling force with respect to that occurring with the use of traditional barrels, while at the same time ensuring a practically unchanged shot exit velocity.
Another purpose of this invention is to produce a smooth bore rifle barrel capable of allowing the usage of a single family of interchangeable chokes, both on traditional and on enlarged rifle barrels.
A further purpose of this invention is to produce a smooth barrel bore whose internal thickness would keep the convergence of the rifles' double-barrels unchanged with respect to that of traditional barrels, thus achieving a favorable shooting precision.
Not the last purpose of the invention is to build a smooth bore rifle barrel in an essentially simple and inexpensive manner, without affecting the dimensions of encumbrance, the esthetic appearance and elegance of traditional rifles.
These purposes are attained by a smooth bore rifle barrel according to claim
1
, which is being referred to for brevity.
In an advantageous manner, the particular geometry of a rifle portion known as “the muzzle”, meaning the area just before the final choke, as well as the lengths of the conical and cylindrical portions present inside a barrel allow achieving an optimum regularity of the internal ballistic phenomenon and of the exit velocity and distribution of the gunshot.
REFERENCES:
patent: 1944883 (1934-01-01), Gerlich
patent: 2465962 (1949-03-01), Allen et al.
patent: 2828569 (1958-04-01), Steane
patent: 4058925 (1977-11-01), Linde et al.
patent: 61107 (1939-03-01), None
patent: 800052 (1936-06-01), None
patent: 854516 (1960-11-01), None
patent: 374653 (1940-01-01), None
patent: 6101993 (1994-04-01), None
Hedman & Costigan ,P.C.
Johnson Stephen M.
S.p.A. Fabbrica Bresciana Armi
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