Open Bolt

The open-bolt version should be cut to length with both ends squared. A boh nose is turned on one end «if the holt body. Iliis should extend 1 50 inch forward from the bolt body proper and have an outside diameter of .550 inch if used as a 9xiun. The .45 version should be .650 inch. A counterbore slightly larger than the cartridge head is cut .100 inch deep. This should have an inside diameter of .400 inch for the 9mm or 480 inch for the .45. In the center of this, a fixed firing pin. 060 inch in diameter, is formed. This should have a hemispherical point and protrude .050 inch from the bolt face. A fairly simple way to form this is to chuck an open-center, or non-ccntcr-cutting 3/8-inch end mill, in the lathe tail stock driJJ chuck. With the bolt turning in the head stock chink, the end mill is fed into the bolt face with the tail stock. This will form the inside diameter some .020 inch to .025 inch undersizc

J-rorn left, full-length 5o!t. open-boic assembly, closed boil 4fsscinbiv

ijy a

en o

Homemade Open Bolt Pistol

Diagran rl'\

Homemade 9mm

Magazine deamnce is cut with en J miff.

End view showing bolt nose configuration.

ill the case of ihe 9mm, and the open center of the milling cutler will leave a small projection that can he turned to form the firing pin using a lathe cutting tool ground to form it. The Outside cutting edge of this same tool is used to hring the counterborc to the correct diameter.

With this accomplished, the bolt is reversed in the lathe chuck, whereupon a hole of sufficient size to accept the recoil spring is drilled, as shown in Diagram ft4. Ihe hole diameter should he slightly larger than the spring used to assure free movement of the spring as it compresses.

In ihe prototype gun, the spring used measured .375 inch in diameter. The hole was drilled with a *Wr drill measuring .386 inch in diameter. A 25/64 drill, which measures .3906 inch, would be equally satisfactory. A slight bevel should be formed at the entrance of the hole, which will assist in reducing friction and binding.

While the boll is chucked in this position, the rear end of the body can be reduced in diameler as shown in the diagram. This is required to allow the bolt to travel entirely to the rear of the receiver, with the smaller-diameter portion moving freely inside the rear mounting bracket.

Ihe bolt is now secured in the milling machine vise and a slot cut down the exact center

Magazine deamnce is cut with en J miff.

using a 5/8 inch end mill. The slot should be cut to a depth that just meets the outside diameter of the bolt nose and a length of 2.250 inches. Upon completion of this, a deeper slot is cut along cach side of the cavity using a 1/8-inch end mill. 1 hese are to provide clearance for the magazine lips and the ejector. The slot on the extractor side should be cut to a depth slightly less than thai of the inside counterborc. The other side must be cut approximately .100 inch deeper to clear the extractor. Properly done, this will leave a strip 1/4 inch wide that is the same depth as the bottom of the bolt nose. I hese slots must be cut long enough to clear the back side of ihe magazine on the one side and the rear of ihe extractor on the other. Next the bolt is rotated 15 decrees and a cut made down the side. It is then rotated back 30 degrees in the oilier direction and a matching cut made. Iliese will closelv match the magazine sides while providing ample clearance between the bolt and magazine.

The extractor cut is made with a 1/8-inch end mill in a len o'clock position when viewed from the front. Ihe slot should be cut lo the inside edge of the bolt nose counterborc. A spring pockei is cut to the same depth at the extreme rear end of the slot using a .VI 6-inch end mill.

be suspended over a bluing tank burner and heated. Actually the term "annealed" is a misnomer as used here, since ihe hardened material can Ik- made workable by heating it to a temperature of 800 to 1,000 degrees and allowing it to cool slowly.

4130 seamless tubing, as used here, can be ordered from I he following supplier:

Wicks Aircraft Supply 410 Pine St. Highland, IL 62249

Homemade Open BoltExpedient Homemade Firearms

Led/ springs <ire the source qf hettf-irea/aMe flat stock.

This is the best source of supply for not only the tubing but also 4 1 50 and 4340 round stock. Coil springs «re avaihhlc from uutoviiotive supply houses as well as flat stock of the same material. Not timl hurefwor*$'(<#0 only are they a source for all of the heat-treatable steel required, hut these are nice people. Anyone who has dealt with large, arrogant steel companies who don't really want to deal in small amounts of material anyway will appreciate this. Another plus is that they will ship by UPS, COD, usually within 24 hours of the limr the? order is received.

Led/ springs <ire the source qf hettf-irea/aMe flat stock.

Suhl 150 22lr




Gun Silencer Diagrams









Expedient Homemade Firearms Thompson

Op*M bolt I (eft) shows fixed finn4cj ptn. Closed boll! nght i ihou^/mng pui bote

Was this article helpful?

0 0


  • fre-weini medhane
    How to make homemade automatique 22lr?
    8 years ago

Post a comment