So, in the time between the suppressor design that I am doing for work, I decided to go after a semi clandestine manufactured SMG. The criteria driving the design is that round tube is incredibly common in SMG designs, so I wanted to avoid that and use rectangular tube and bar stock. This minimizes the operations that require a lathe, and while they ideally would be done on a mill, they can be accomplished with a drill press and hand tools if you have the patience. Some of these parts are innocuous enough that they could also be farmed out to local machine shops without raising eyebrows. Strangely, one of the larger issues that has faced clandestine small arms manufacturing is an acceptable human interface. Other people solve this by traditional methods such as carved wood grips, or cast/molded plastics, but that is a time consuming process to make a part that should be very simple. My solution was to use handlebar grips from a bicycle. They are already designed to provide a griping surface for your hands, and they are common enough and varied enough that you could will not have a problem sourcing them.
As far as the design goes, it is still a work in progress. The receiver is pretty much dialed in, as are the trunnions, the barrel, barrel retention system, etc. The FCG has been a sticking points, as designing them is probably my greatest weak point when it comes to arms design. As the FCG is horribly incomplete, the bolt may similarly undergo changes. It is currently planned to have a linear hammer, but that is still in the works. I have only begun to consider what to do for the stock, and the forearm will probably come last. The design uses Uzi magazines, and I'm toying with the idea of being able to change magazine compatibility by having alternate lower receivers.
There are two primary versions; the 9" barrel original design, and the 5" barrel design.
Charging handle/bolt/action spring interface
Early receiver, designed to be cut out of 1x2" 11ga rec steel tube. The notches near the trunnion and front barrel support are to allow the components to be welded together.
charging handle and barrel retention system details. The action spring guide rod runs through the front barrel support and in conjunction with the receiver it locks the barrel retainer plate in place. The retention plate slips into a grove cut into the barrel. This prevents the barrel from moving backwards out of the receiver, while the square section at the breech of the barrel nests in the trunnion to prevent forward movement. The barrel is not rigidly fixed to the receiver, but this is acceptable considering the intended applications of the weapon.
The full title of this work is "Weaponeering - Conventional Weapon System Effectiveness" by Morris Driels, who teaches at the USN Postgraduate School, and the cover of the edition I have in hand can be seen below.
The book aims to "describe and quantify the methods commonly used to predict the probably of successfully attacking ground targets using air-launched or ground-launched weapons", including "the various methodologies utilized in operational products used widely in the [US military]." Essentially, this boils down to a series of statistical methods to calculate Pk and Ph for various weapons and engagements.
The author gave the book to my mother, who was a coworker of his at the time, and is of the opinion that Driels is not as smart as he perceives himself to be. But, hey, it's worth a review for friends.
I will unfortunately be quite busy in the next few days, but I have enough spare time tonight to begin a small review of a chapter. I aim to eventually get a full review of the piece done.
Our dear friends @Collimatrix and @N-L-M requested specifically chapter 15 covering mines, and chapter 16 covering target acquisition.
The mine section covers both land mines and sea mines, and is split roughly in twain along these lines.
The land mine section begins with roughly a page of technical description of AT vs AP, M-Kill vs K-Kill, and lists common US FAmily of SCatterably Mines (FASCAM) systems. The section includes decent representative diagrams. The chapter then proceeds to discuss the specification and planning of minefields, beginning with the mean effective diameter of a mine. Driels discusses a simplified minefield method based on mine density, and then a detailed method.
The simplified method expresses the effectiveness of the minefield as a density value. Diels derives for the release of unitary mines from aircraft
NMines = Fractional coverage in range * fractional coverage in deflection * number of mines released per pass * reliability * number of passes
and for cluster type
NMines = FRange * FDefl * NDispensers * Reliability dispenser * NMines per Dispenser * Reliability Submunition * number of passes
and then exploits the evident geometry to express the Area and Frontal densities. Most useful is the table of suggested minefield densities for Area Denial Artillery Munition and Remote Anti-Armor Mine System, giving the Area and Linear densities required to Disrupt, Turn, Fix, and Block an opponent.
Whereas the simplistic method expresses effectiveness as a density, the detailed model views the targets and mines individually, assuming the targets are driving directly through the minefield perpendicular to the width and that there is only one casualty and no sympathetic detonations per detonation. The model computes the expected number of targets destroyed by the minefield, beginning with the Mean Effective Diameter and the PEncounter based on distance from the mine.
Driels derives the number of mines encountered which will be encountered, not avoided, and will engage the target. I can't be arsed to type the equations in full, so here you go.
The section concludes with an example calculation using the detailed mine method. Overall, this shows the strengths and weaknesses of the book fairly well - it is a reasonable derivation of open-source statistical methods for predicting Pk and Ph and the number of sorties required, but US-specific and limited in scope and depth.
The treatment of Sea Mines begins by describing the various types and uses of said mines, importantly noting that they have both defensive and offensive uses, and that the presence of the threat of mines is equally important as the actual sinking which occurs. There are three classifications of sea mines, contact, influence, and controlled.
Shallow water mines are treated trivially, considering them equivalent to land mines with Blast Diameter in the place of MED, and assuming that the mines cannot be avoided.
Deep water mines are approached in a similar manner, with the desire to determine the number of mines needed to achieve the required probability of damage, and planning missions from there. Two features of sea mines must be considered, however - mine actuation by passing of the target, and mine damage to the target. The probability of activation is, unfortunately, dependent on the depth of the mine and distance, forming a series of stacked bowls as below.
The mean value of PActivation is the statistical expectation of the curve. Because I don't feel like screencapping another equation, the Width of Seaway where an actuation can occur is qualitatively merely the area under the actuation curve calculated for a specific mine and target combo.
The damage function is also of interest - because we require the mine to both actuate and damage the target, this limits our earlier area under the curve to that area integrated to the limits of the damage function. The selection of mine sensitivity plays a very large role in the effectiveness of our mines. A high setting will lead to many more actuations than damages, which can be indicated by the ratio of the actuation area and the damage area from earlier. Setting the actuation distance equal to the damage distance means that every actuation causes damage, but the probability of actuation is only around 42%. The compromise which selects some Areadamage / Areaactuation of around .8 to .93 is generally preferred. This gives us several useful terms -
PA+D = Reliability * Areadamage / Widthminefield . The probability that the first ship to transit a minefield is referred to as the threat, or
Threat T = 1 - (1 - PA+D)^NMines = 1 - (1 - Reliability * Areadamage / Widthminefield ) which can obviously be solved for NMines to get the desired number of mines for a desired threat level.
Anti-submarine mines are an interesting subset of deep sea mines, as they turn the problem from two-dimensions to three. Driels accounts for this by replacing the mine damage width with the mine damage area, to no one's surprise. Driels claims that the probability of actuation and damage is
PA/D = Damage Area / (Width * Depth of minefield). Despite my initial confusion, the reliability term safely reappears in the threat definition below.
T = 1 - (1 - (Reliability * Area damage)/(Width * Depth of minefield))^NMines, with a solution for number of mines for given threat level fairly easily taken out as before.
Lastly, there is a summary of topics for each chapter, though unfortunately they are qualitative descriptions. Including the final derived equations in this part would be a major benefit, but is overlooked. Ah well. They are quite good for review or refreshing the material.
As before, this is a relatively interesting if shallow engagement with the statistical methods to calculate Pk and Ph and the number of sorties required. Going more into detail regarding selecting Threat values or common (unclass) parameters would be interesting, but is lacking. Assuming I don't slack off tomorrow, I should have most or all of the Target Acquisition chapter covered.
Anti-air bobcat design to take away driver's hearing in maximum efficiency
SH11 155mm SPG