When warming a muzzle before casting a lap, consider the front sight. If attached to a ramp or band that is sweated on with solder, use care to avoid melting the solder. Better warm the barrel, in such case, with rags wrung out of boiling water.
When pouring the lap, maintain a steady stream until the muzzle is full. If you stop- pouring for an instant the lap may be in two pieces.
Keep a sufficient quantity of lead melted all during the job, and change laps frequently. A full tight lap is the secret of a good job.
After two or three strokes the lap runs much easier in the barrel, and one may receive the impression that the abrasive is not cutting —but it is. A lap should be good for five to ten minutes of continuous work with emery flour, and several times that long with the polishing abrasives.
If considerable enlargement of the bore is desired, it will be found practicable to start the job with the finest grade of water-mix valve grinding compound, obtainable from auto supply dealers and garages. Do not use.this for more than five minutes, then cast a new lap, and lap with fine emery flour before measuring, as the valve giiuding dupe leaves a somewhat rougher surface difficult to measure with a lead slug. If the measurement shows more enlargement is needed, use the valve dope again, until within 1/2 thousandth of desired diameter. Then finish with emery flour and the polishing agents.
Stazcn Rustoff and Winchester Rust Remover are very good for the first polishing following the final lapping with emery flour.
Always clean out the barrel perfectly clean after each lapping, before casting a new lap, or starting on a finer abrasive.
Clean the lapping rod with oil and wipe dry after each lapping.
Never, under any circumstances, lap a barrel from the muzzle.
Make the lapping rod from tool steel drill rod, of the maximum diameter that will pass easily through the bore. A thin or weak rod will buckle under pressure and rub against the walls of barrel, damaging the rifling.
LAPPING CHAMBERS: Generally speaking, this is a job that should never be attempted cither by the amateur or the professional gunsmith, except under unusual circumstances. There are exceptions, however, as will be explained.
A friend of mine procured, at bargain price, a three-barrel gun, the rifle barrel measuring about .303 caliber, but chambered for some sort of "bastard" cartridge which we could neither identify nor locate. The .303 British cartridge would almost—but not quite enter the chamber. A sulphur cast disclosed that the chamber was just slightly smaller than the regular cartridge at the shoulder, the neck and head dimensions being practically the same. Chamber reamers were not available in this caliber, but the following simple expedient proved effective:
Bullets were pulled from half a dozen new .303 British cartridges, the powder removed and the primers snapped. The heads were drilled and tapped to take the threaded end of a piece of 1/4 inch drill rod 2 inches long. This was then screwed into one of the empty cases, and the other end of the rod squared with a file. Another piece of rod three inches long was chucked in a hand drill, with the projecting end squared, then the two rods connected by a piece of heavy rubber tubing slipped over the ends, giving a flexible connection. Water-mix valve grinding compound was then applied only to the shoulder of the case, which was carefully inserted in the chamber and revolved by turning the drill handle. The drill must be drawn back frequently, and very light pressure used, otherwise the tapered case may "freeze" in the chamber. When the case showed any considerable wear it was discarded and a new one used. Finally, when a case had been lapped in to within 1/32 inch of being fully seated, a new one was used with emery flour and oil, this being lapped in until the action would barely close on an empty case, but requiring excessive pressure. Winchester Rust Remover, pumice and oil, Tripoli and rotton stone were then used in order named until the loaded cartridges just seated correctly. The chamber was very highly polished by this operation, and ejection was perfect. Thus a useless gun was put into service at very small cost, the whole operation not requiring more than an hour and a half.
After the first case had been lapped in, the necks were cut off the other cases to prevent enlarging the neck of chamber, and every time a new case was used the chamber was washed out clean with thin oil.
Unless head-space gauges are available I would not recommend lapping the chamber of any high power rifle using rimless ammunition, as it would be a simple matter to increase head-space to the danger point without realizing it. If attempted, it should only be done with the finest polishing abrasives, and should be carried only far enough to remove any reamer marks and polish the chamber walls. The best plan is to forget it.
Chamber lapping may sometimes be profitably employed in revolver cylinders. It is well known—to handloaders at least—that very often the chambers in one cylinder will vary sufficiently in size so that the case that has been fired in one chamber will not readily enter some of the others. This necessitates full length resizing cach time the eases are loaded, and die 1 exulting fatigue greatly shortens the life of the brass.
A sulphur cast should first be made of each chamber, and each cast carefully measured with the micrometer. The operation then is to lap all chambers to the same size as the largest. The same arrangement is used as described for lapping the rifle chamber, except that fired cases are used instead of new 0ft«.
■396 tion. The hammer is held in the cocked position by the sear engag-
Sefect the case fired in one of the chambers that is about midway ing in a notch. The sear may be a separate part, or it may be the in size between the largest and the smallest. Using only emery upper end of the trigger itself.
flour and oil, lap it into the smallest chamber. Then lap into this In the plain trigger which has the seax made integral, the trigger same chamber the fired case from the largest chamber. By careful is pivoted by means of a pin or screw between the upper end which selection of fired cases you can lap all chambers to the same size, forms the sear, and the lower end to which the pressure is applied then cast a lead lap in the largest chamber, and coat it with emery by the finger. Thus, the trigger becomes a lever of the first class, flour and oil, going dear round the cylinder and using this lap three the tension formed by pressure of the hammer notch on sear forming or four revolutions in each. Wash the lap clean-^r better, cast the "weight;" the pivot in pin or screw forming the "fulcrum,"
a new one, and go the rounds of all chambers using the finer polish- while the finger supplies the "power" at the lower end.
ing compounds. This simple treatment will result in the fired cases When a separate sear is interposed between trigger and hammer, from any chamber fitting all of the others, and will eliminate the a double system of leverage is formed, and the trigger is usually a tiresome operation of full length resizing entirely. Care must be lever of the second class, i. e., with the weight located between the taken not to enlarge the largest chamber at all—only polishing it fulcrum and the power—the weight in this instance still being with the same lap used in the others to assure all being exactly the supplied by the pressure of the hammer, and transmitted to the s**??**2*'. . , , , trigger through the scar. The sear may be a lever of cither the
When lapping a cylinder it should of course be removed from first or second class, according to the design of the mechanism.
lheJICTolver *** hcld wilh brcech end uPri8ht in thc vi5C- Figure 165 illustrates the three types of levers known to physics.
The amateur doing his first job of chamber- lapping may be In a lever of thc first class, it will be evident that if the fulcrum is tempted to attach the lap to a motor shaft in the hope of speeding located midway between the weight and the power, the power re-
807 would have to supply a pressure greater than that exerted by the
Chapter 28 liammer. Now the pressure of a stiff hammer spring, stiff enough afititctiwr tvirrrv pitt r c aS$Urc a?ains? 1misfircs> is considerable. (Try cocking your rifle
AL>J Uo 1 liNCj IKIUUkK rULLb by means of weights suspended from the hammer or cocking piece).
Such a pull would not be conducive to good shooting, to say the
A JOB frequently required of both amateur and professional gun- least ; so, the required "power" or finger pressure is reduced by
-^smiths is the adjustment, usually for the purpose of lightening locating the trigger pivot much nearer the sear point than to the and shortening, of the trigger pull. Most rifles, shotguns and pistols as finger point.
they come from the factory or armory, require such adjustment. D _ . .. .. . • j • u 1 tu —
Some men have such a perfect sense of touch that they can use a very But ,n no}hw« «ained without some loo. The nearer light pull ,0 advantage; «hile others need a heavy pull due to a ™ piv?' ^ the s"r 7"1' the,le*? "
' <>]'. -vn.-nVnr» t0 "rc l"c £un« but the movement, thc travel, of the lower end ot nervous tendency to loose ott prematurely. 1 ne experience 01, . , . . T . . , _ .
. y , . : y . j r __the trigger, is increased in direct ratio. Likewise, the shorter the many target and game shooters over a long period of years has shown &te, * . . . . , . / , ,____
that the best trigier pull for all round uie is one retiring press,,« d'f,nce the s"/ m.u" move be ore ,t released from the hammer of from 2 1/2 to 4 pounds to discharge the piece. The pull should notch-or, puttmg lt ,nverselr- the ,tss the hamra" iecE,vo fth°Ut tHe lea.',t1SUSpici°ri °f dr3g u' °reCP' ' ADJUSTING "HAMMER ACTION" TRIGGERS. Tak-
should be absolutely no perceptible movement in the trigger until . f , . , ____, . , , . .
¿-ill* An ♦V»*» nrceonnf »-Km fir»rrt»r io crra/liiallv in- ' ^ '^fg , t C (7V f (
the hammer falls. As the pressure of the finger is gradually in creased, the trigger should suddenly release, like the snapping of a thin glass rod.
p in gjass roa. j
There is a deal of misinformation in the minds of certain shooters, J^ (w)
acquired as a result of the limited training they received during thc i --
Wo rid War, or later in the Civilian Training Camps. All service rifles, as issued, have long, heavy trigger pulls, with considerable creep on the final take-up. Plainly it is impossible to give these rifles the fine adjustment which the individual bestows on his own gun. N
So the rank and file are taught to overcome this mechanical defect (w}
by slowly squeezing out this final drag when firing on the range— ] ] g in other words, they are taught to endure what cannot conveniently ^ ~2S~
In every walk of life there is a large percentage who have never P
learned, and never will learn, to think for themselves; and these ___^
brethren will stand up and tell you they like a pull with plenty of (yy) creep in it, because that's the kind of pull they had on their rifle at r5-^-
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