#OpenBolt

Welcome back to another edition of The Rimfire Report! This ongoing series is about the rimfire firearm world and its many types of rifles, handguns, ammunition, and shooting sports! In the last installment, we brought you all back a bit in time to when the Mitchell Arms company produced one of the most unique and fondly remembered 50-round rotary drum magazines for the Ruger 10/22 rifle. Many people who have owned these, including those of you in the comments, lamented that while they have great memories of shooting with these unique 50-rounders, most of you have stopped due to concerns over the deterioration of the bolt, and other plastic components. I suppose for now they’ll just have to remain a nice rimfire junkie’s collector’s item. This week we’re headed to France, or rather talking about a French-made gun that is not only really rare in the United States, but rare for rimfire firearms in general. We’re talking about our titular firearm for today’s Rimfire Report – the Gevarm series of open-bolt 22LR semi-auto rifles.

Kalashnikov Media has published a video showing a very interesting AK-47. This is an experimental Type 1 AK that has some design changes done by Mikhail Kalashnikov himself. The experiments were done in the early ’50s, shortly after the adoption of AK-47 in 1949, in an attempt to find ways of improving the weapon’s performance, especially when firing in full auto mode and from unstable stances.

The Demro XF7 Wasp is one of many iterations of the Demro Tac-1. It is a pistol caliber carbine. The Wasp features a folding stock. What is more interesting is that the Tac-1 is one of the few open bolt firearms grandfathered by the BATFE.

For those of us so blessed to have served with open-bolt machine guns, we know that clearing malfunctions can be a real chore. Where standard shoulder-fired small arms like the M4 are truly difficult to get to cook-off temperatures, belt-fed weapons can get to those short, fast, and in a hurry. In fact, this is the very reason why (including accelerated barrel wear) that most belt-fed weapons have a provision for quick barrel changes.

SLR Rifleworks posted up this photo to reminisce a build they did many years ago.

Jim of Burst Review got a Cobray Terminator to shoot from his friend Lee Cap. For those not familiar with the Cobray Terminator, it has been touted as the world’s worst shotgun. At first glance it looks like a modified Sterling SMG. However it is chambered in 12ga.  The Sterling SMG is an open bolt design and so is the Terminator. However they are nothing alike. The Sterling SMG open bolt is a traditional open bolt design. The bolt is locked to the rear and pulling the trigger releases the bolt forward and fixed firing pin at the end of the bolt is what sets off the round. In the Cobray Terminator there is no bolt. The receiver end cap houses the fixed firing pin. So when you chamber a 12 ga shell and pull the trigger, the entire barrel travels rearwards pushing the shell back into the firing pin. This adds additional force to the recoil of the gun making it worse to shoot than standard single shot shotgun.

Here is an interesting patent ( US4019423) for an open bolt assault rifle which looks like a cross between a STEN and an M16. A large compression spring is depicted in front of the barrel assembly which in theory will slightly delay the breech opening when struck by the bolt as a round is chambered. A very simple concept on paper, though I can see a hang-fire not being too pleasant.

The period from 1945-1970 did not represent the figurative finest hour in US small arms design. From the problematic M60, to too little too late M14, to the disastrous initial fielding of the M16, US small arms design during the time seemed to simultaneously reach to far and grasp too little. One family of firearms that was a product of this period of development was a short-action armored fighting vehicle secondary machine gun design, incarnated in the M73 7.62mm and M85 .50 caliber, and later M219 7.62mm types. (EDIT: I don’t really think the M85 should be thrown in there, as it’s a substantially different design, though it shares some features with the M73 and M219. Mea culpa.)

Since I got into machine guns one of the most unusual things I have noticed is that an astounding amount of people who shoot most commonly available submachine guns will get ready, anchor their feet into the ground, cock the bolt to the rear, and then look at me confused and say “it won’t cock” or “the bolt won’t close”. I used to simply say “oh, it fires from an open bolt,” but that typically led to more confusion, even among people you would assume would be familiar with that type of action (including military folk and police officers). Hell, I have been to competitions where the range officer was insistent upon me walking around the range with the gun’s bolt open in the ready to fire position, even though I explained how the bolt closed with no mag in it is correct and that to render the gun completely safe I would have to remove the magazine and walk the bolt forward. Nowadays instead of explaining how an open bolt gun works I just say “it’s fine, just pull the trigger” and people will shrug it off and dump a magazine.