Firing And Adjusting

With the component parts finished and colored to your satisfaction and reassembled, the project should be ready for tcst-liring. It might be assumed that* since the gun was assembled and semi test-fired before heat-treating and finishing and seemed to work ihe way it was supposed to, it will still do so. Ibis may or may not l>e the case. Parts sometimes grow or otherwise change shape while being heat-treated. This can also happen when certain types of coloring techniques arc practiced. Still others lend to etch the surface of the metal, leaving it slightly rough, in many cases, parts that moved freely around pivot pins during the first assembly will no longer do so.

When testing the closed-boll version, make sure that the extractor will still open far enough to snap over the cartridge rim and hold the case head against the holt face. If it docs not. check foi burrs or other roughness and make sure the pivot pin still works freely through the hold in the extractor.

The firing pin should be examined carefully to make sure that it doesn't stick in its forward position and that it retracts fully when not in contact with the hammer.

Don't overlook this. One time, earlier on. 1 earelesslv assembled a bolt similar to the one used m here, assuming that, since it worked before I blued it, it still would. When I inserted a magazine with two rounds in it, retracted the bolt, and let it slam forward, both rounds fired, even though the safety was engaged and the trigger wasn't touched. Subsequent examination revealed that a solidified lump of the nitrate salts 1 used to blue the gun was lodged in the firing pin hole and had jammed the firing pin in its forward position, effectively causing it to become a fixed firing pin. Another time I test-fired a 9mm pistol of similar design. This one had been fired numerous times several months before. It had worked perfectly then. Bui this time, when I let the bolt go forward, all five rounds in the magazine fired. Examination showed that the firing pin retracted just the way it was supposed to and moved back and forth without binding. When the action was cycled slowly by hand, the hammci remained cocked until the trigger was pulled. It was eventually discovered that the sear pivot pin had rusted, causing just enough drag that although the hammer remained cocked during I he forward movement of the bolt, rhc jarring effect when the bolt slammed fully closed caused the hammer to slip off of the partially engaged sear. This, in effect, resulted in a closcd-bolt. hammer-fired machine gun These experiences prove three things: first, thai 1 am not perfect; second, that I should have loaded onlv one round for tcst-liring, as I have advocated here, and third, that nothing should be taken for granted. Always check these things carefully, and when test firing, keep the muzzle pointed downrange.

The first test firing should be done bv inserting a magazine coniaining a single round, retracting the bolt, and allowing it to slam forward unimpeded, as it would in the firing cycle. It should push the round out of the magazine and into the chamber. Before firing is attempted, retract the holt slightly to ascertain whether the extractor snapped in place over the cartridge rim. If ii didn't, the spring is too stiff or there is mechanical interference, which should be corrected before test-firing proceeds further. Iliis will usually be done by substituting a weaker extractor spring or locating and removing metal from the place where interference or contact occurs. Usually, coating the exposed extractor surfaces with lipstick or the like and working the bolt a couple of times with a cartridge in the chamber will show where the problem is.

If the bolt closes cumpletely and the extractor works the way it is supposed to, the gun should be held so thai it points away from you and any close spectators and the round fired. Ideally, the iound will fire and the bolt will travel to the rear, ejecting the empty case in the process, and move again to the closed position.

Failure to fire can be caused by several things. Perhaps the firing pin is too short. This can be checked by removing the barrel, and. with the hammer forward against the base of the firing pin, measuring from the face of the receiver to the boll face Another measurement is taken from the face of the receiver to the proLruding firing pin tip. I his last measurement is subtracted from the first, and the result will be the amount of firing pin protrusion, which must be at least .055 inch. If it is ncit, the shoulder in the firing pin hoU\ which limits its forward travel, must be deepened a corresponding amount.

Failure to fire can be the result of the chamber being cut too deep, also known as excessive head space. (Co back and read what I said about this earlier. • This condition can be corrected by cutting back Lhe front edge of the receiver an appropriate amount. This will allow the barrel to move farther hack into the receiver. The same result can be achieved hy cutting hack the front facc of the bolt hody not the small, countcrborcd bolt-nose portion, hut the laTgnr outer body. Either of these actions will close- the gap between the barrel and chamber and the bolt face, which, when dune in the required amount, will correct I lie excessive head space.

As it turns out. though, the round does lire, due mainly to your precision workmanship and attention to detail. So we c an now load two rounds and try it again. If hoth lire and cjcct, five rounds should be loaded and fired, followed by several loadings of not more than ten. Full magazine loadings should be postponed until a hundred rounds or more have been fired, which will tend to loosen up the action and smoulh out any rou^h spots or burrs still present. A iully loaded magazine increases friction against the reciprocating holt and may very well slow it to a point where it doesn't open completely. Thus, the break-in period to loosen it up.

It may very well be that even after a break-in period the action doesn't open completely when the magazine is fully, or almost fully, loaded. I his is evidenced hy failure to eject empty < ^scs and/or failure of the bolt to open far enough to pick up the next round from the magazine. This can usually be cured by shortening lhe recoil springs, which should lie done slowly, a coil or two at a tunc, test-firing each time, until the bull opens completely. This too has its drawbacks, in that enough spring pressure must remain to close the hiilt completely. So don t overdo it.

I he open-bolt version is tested and adjusted in essentially the same way, cxccpt. of course, that inadequate firing-pin protrusion can be ruled out as a cause of failure to fire. This time, the bolt should remain open when it reaches the end of its rearward travel while in the semiautomatic mode. Its failure to do so can he caused by an nverlv stiff recoil spring. This is corrected the same way as was done with the closed bolt. Another cause of this can be that the scar facc is angled forward, rausing the boll to cam it down and out of engagement. This surlacc. as well as the surface of the bolt it engages, must be square and Llat.

As described earlier, full aulomatic fire is caused by simply pulling lhe trigger farther to lhe rear, which cams the sear our of engagement, rendering the disconnector inoperative.

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