US2497196A - Micrometer head space gauge - Google Patents

Description

Feb. 14, 1950 L. A. WOODWARD MICROMETER HEAD SPACE GAUGE Filed Feb. 20, 1948 F/G. i.

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/4 ze z5 Patented Feb. 14, 1950 UNITED STATES PATENT OFFICE 2,497,136 MicuoMErnaHEAn SPACE GAUGE LeroyA. Woodward, Dckinson, .'N. Dak.

Application February 20, 1,948, Serial-No. 9,817

(Cl. 33e-.163.)

1 Claim. l My invention relates to gauges for vmeasuring the head space of rearms, andmore particularly toA gauges of the micrometer type which are adapted to be. inserted intothe firing chamber of a firearm to correctly and accurately gauge the distance from the forward shoulder of such chamber to the closure for the rear end of the chamber.

In the manufacture ofv rearms, particularly rifles using fixed ammunition, it is necessary that the longitudinal dimensions of the firing chamber be. extremely accurate, whereby the iixed ammunition will have the snugflt in such chamber with the rear end of the cartridge snugly abutting the forward face of the closure for the firing chamber which usually comprises a bolt. Thus, if the firing chamber is too longftoo much head space is provided which comprises va space between the rear end of the. cartridgev and the face of the. bolt which makes for `the creation. oi dangerous pressuresl when the cartridgeis fired. On the contrary, when the ring chamber is. too short, the cartridge will not extend into it sufriciently, whereby the bolt either will `not close or will not close completely. Consequently; itis of great interest to the manufacturer or gunsmith that the longitudinal dimension vof the ring chamber be extremely accurately gauged, Whereby the head space is proper for the ammunition for which the gun is designed.

With the. foregoing in view, it is. an object of my invention to. provide an improved head space gauge.

A further object of the invention is to prov-ide an improved head space gauge in the form of an interior micrometer which is insertable in the firing chamber ofA a firearm to n ieasure the longitudinal dimensions thereof.

A further object is to provide in a head space gauge, such as that last described, means for locking the beam and the sleeve of the gauge together in a pre-set relation to each other.

Other objects and advantages reside in the particular construction of the device according to the invention, combination and arrangement of the several parts thereof, and will. be readily understood by those skilled in the art upon reference to the attached drawing in connection with the following specification, wherein the invention is shown, described and claimed.

In the drawing:

Figure 1 is an elevation of a preferred form of the invention;

Figure 2 is a view like Figure 1, but showing a portion of the outer sleeve in longitudinal vertical section;

'Figure als. an end view looking from the right of Figure l;

.Figure 4 is a transverse vertical section taken substantially on the plane of the line 4-4 of Figure 2;:

Figure: 5 is an end. elevation of a locking device looking from .the left of Figure 6;

.Figure 6 is a longitudinal vertical. sectionV through the lockingv devicev of Figure 5;

Figure 7 is a longitudinal vertical section through `the. butt end of a rearm showing the gauge according to the; invention in use.

Referringspeciflcally to the drawing, wherein like referencev characters have been used throughout. the several views to designate like parts, and referring more specifically to Figure '7, Ill desigf nates generally the rear end of a barrel for anrearm which. includes the usual bore II which merges with shoulders I2 into a ring chamber I3 at the rear end. The iiring chamber |31 is normally closed at the rear by a movable closure I4, such as a bolt. Any suitable cartridge, not showmhaving a shell case complementary to the shape of `the firing chamber I3 is adapted to be positioned in the ring chamber I3 and. secured therein by a bolt I4 for firing.

The gauge according to the invention comprises a sleeve generally indicated by I5 which comprises` a reduced central section I5 and enlarged end sections. .I8 land I9. The diametric dimensions of theA enlarged sections I3 and I9 are such as to be substantially complementary to the in, terior of the firing chamber I 3. The front section I8- merges into an inwardly-directed substam tially nostro-.conical shoulder vIl which is com! plementaryto the shoulder I2 of the firing cham ber. The reduced central section Iii may be provided w-ith knurling 2B to provide a grip thereon. Obviously, the reduced central section I6 is not adapted to come. in contact with the walls of the .firing chamber I3, whereby to permit the knul-ling` or stamping of markings on the centr-afl section I8, The rear enlarged section I9 may be inscribed with a suitable zero marker 2I.

The sleeve I5 is formed with an interior 'bore Z2 which extends rearwardly from the forward end thereof. The bore 22 is unthreaded and the forward end is outwardly flared to provide a substantially frustro-conical recess 23 which faces forwardly of the front end of the sleeve, Rearwardly, the bore 22 merges into an enlarged and threaded counter-bore 24 which in turn, in the region of the enlarged rear section IB, merges 3 into a still further enlarged and unthreaded counter-bore 25.

A beam 26 is concentrically disposed within the sleeve I 5. The beam comprises a graduated rear end section 2T which is formed with a suitable zero graduation 2t and plus and minus grad uations 2S and 38, Figure 2. The rear end of the section 2l extends outwardly of the second counter-bore 25 and is formed to provide the measuring head 3l. The forward portion of the section 21 is slidable into and out of the counterbore 25 in axial directions. A measuring thread section 32 of the beam 2% extends forwardly of the graduated section 2l and is threadedly received in the interioriy-threaded-counter-bore 24 of the sleeve. A cylindrical forward extension 33 of the beam is slidably received in the bore v22 of the sleeve and includes a terminal portion 34, a, part of which at least extends outwardly or forwardly of the forward end of the sleeve l5. A lock' nut 3S is threaded on the threaded terminal portion 3d of the beam and comprises an interiorly threaded sleeve member having a substantially frusto-conical rear end 36 which is formed with a plurality of radially-directed slots 31. The frusto-conical rear end 36 is adapted to be substantially complementary to the frustoconical recess 23 in the forti ard end of the sleeve l5. The outer periphery of the nut 35 may be knurled or otherwise formed to provide a gripping surface. Such surface is best indicated at 38, in Figure 1.

In operation, the gauge according to the invention is inserted into a iiring chamber i3 of a firearm, Figure 7, with the zero indicia or calibrations 2l and 28 of the sleeve and beam aligned. The bolt or closure it for the firing chamber is now closed. Assuming that the firing chamber i 3 involved is too short, the bolt will either refuse to close entirely or will close only with a substantially great effort. This indicates that the firing chamber is too short, as the gauge when set with the zero indicia aligned is of the correct length to correspond to the cartridge designed for use in the particular gun. It should be mentioned at this time that prior to inserting the gauge into the firing chamber initially, the sleeve and beam are locked in the Zerindicating position by 'means of the lock nut 35 which is screwed down so that the spring end formed by the slots 3l is forced into locking and wedging engagement with the recess 23 oi' the sleeve and the threads of the threaded portion 34 of the beam. Upon the determination that the firing chamber I3 is too short, as aforesaid, the gauge is removed from the firing chamber, and the beam 25 is screwed ina' direction to shorten the length of the same and register one of the minus graduations 29' of the beam with the Zero indicator 2l of the sleeve. The lock nut 335 is once more tightened to lock the parts together and the gauge is reinserted in the ring chamber and the bolt is again closed. Assuming that the bolt now works freely, the setting of the gauge is noted, the lock nut is loosened, and the gauge is reset at an intermediate point between. the last reading and the Zero settings. Once more the gauge is inserted into the ring chamber, and the bolt closed. Assume ing now that the bolt again works 'too tightly, the setting is once more noted and the new setting of the gauge is made until the proper and accurate measurement of the longitudinal dimensions of the firing chamber is accomplished. The gauge will then indicate in the example described the amount by which the firing chamber I3 must be enlarged by boring away of the shoulder I 2 thereof to insure proper head space between the rear of the cartridge and the forward face o the bolt i4. Obviously, when the initial test o the firing chamber indicates that the same is too long, the procedure is reversed until there as been determined the amount by which the firing chamber must be shortened by sawing off the rear end of the barrel I0.

By providing means for locking the moving parts of the gauge together during a, measuring operation, extremely great accuracy is obtained and there is no danger of inaccurate readings caused by relative rotation of the parts during the opening and closing of the bolt and/or in the insertion or removal of the gauge from the chamber. Wear of the gauge parts is readily compensated for by setting the same to a position where it correctly designates the correct size of a desired iiring chamber and then remarking the sleeve part i9 with a new zero setting 2| in alignment with the zero calibration 28 of the beam.

Thus, while I have shown and described what is now thought to be a preferred embodiment of the invention, it is to be understood that the same is susceptible of other forms and expressions. Consequently, I do not limit myself to the precise structure shown and described hereinabove except as hereinafter claimed.

I claim: l

In a head space micrometer for measuring the distance from the internally shouldered forward end of a ring chamber to the forward end of a closed breech closure, including an internally threaded sleeve substantially complementary to said chamber and having front and rear ends, a beam having external threads at an intermediate portion thereof, said beam being threaded in said sleeve and having front and rear ends extending axially outwardly of both ends thereof, and a head formed on said rear end of said beam for engagement with said closure, the improvement comprising other screw threads formed on said front end of said beam, a lock nut threadedly and adjustbly engaged with said last named threads, said sleeve including a. forward end formed with a forwardly-directed frusto-conical recess axially thereof, said lock nut including a rear end formed with a rearwardly-directed frusto-conical sleeve engaging end, and said sleeve engaging end of said nut being wedgingly seatable in said recess, whereby to lock said beam and sleeve in pre-set relation to each other.

. LEROY A. WOODWARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 729,970 V4Spalding June 2, 1903 1,351,721 Eickhoff et al.\ Aug. 31, 1920 2,340,428 Ramsdell Feb. 1, 1944

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