The tround is an unique firearms cartrige developed by inventor David Dardick for use in his open chamber firearms. Named for it's convex triangular shape, the tround allowed the firearm's chamber to be open on one side, removing the requirement for reciprocating motion when chambering and ejecting a cartridge. An assortment of modern hand-held firearms using fixed ammunition, including military assault rifles, a sporting shotgun (fourth from bottom), a tactical shotgun (third from bottom), and a sporting rifle (top). ... This article does not adequately cite its references or sources. ... For other uses, see Inventor (disambiguation). ... Look up convex in Wiktionary, the free dictionary. ... A triangle is one of the basic shapes of geometry: a polygon with three vertices and three sides which are straight line segments. ... Reciprocating motion is a back and forth (or an up-and-down) motion which repeats over and over again. ...

Open chamber firearm design

Patent drawing of open chamber gun

Dardick's patent 2,847,784, issued in August of 1958, is for a pre-stressed open chamber gun with rotatable cylinder. Essentially this design was a revolver with the exterior of the chambers opened up, forming an open U shape rather than a closed O shape found on typical revolvers. This allowed cartridges to be inserted from the side of the cylinder, rather than from the front or rear, and allowed the cylinder to be rapidly loaded from a magazine. Year 1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ... rEVOLVEr (2004) is the fourth studio album release by Swedish thrash metal band The Haunted. ...

To contain the pressure of firing, an odd number of chambers (typically three) are milled into the cylinder. The cylinder is placed, centered, in a strong frame, so that when ready to fire, the cartridge rests against one side of the frame, and the opposite side of the cylinder rests against the opposite side of the frame. Upon firing, the force is spread to the frame from the cartridge on one side and the cylinder from the other. The pre-stressed part of the design applies to the frame; it is assembled from two parts, which are machined so that the exterior part must be heated, thus expanding, before the interior part can be inserted. Upon cooling, the exterior part contracts, putting the interior frame under compression. This compression counters the pressure put upon the frame by firing.

Unlike a traditional firearms cartridge, whose case is roughly cylindrical, the open chamber requires the cartridge to be otherwise. Since the cartridge contacts the frame upon firing, one side of the cartridge must match the curvature of the cylinder's exterior, while the other side of the cartridge must match the half-chamber of the cylinder. Together, the cylinder and frame form the chamber, and the cartridge must not only fit in this space, but also must seal it upon firing, and not deform to prevent cylinder rotation.

At this point the rounds are not the familiar three sided shape seen in Dardick's production firearms. They are, rather, cylindrical on one side (the side facing the cylinder axis) and nearly flat on the other (The side facing the frame). This patent defined the open chamber gun concept, however, and quickly lead to the development of the tround.

Tround development

Patent drawing of tround

Dardick's patent 2,865,126, issued in late 1958, is for a new and improved cartridge for the open chamber gun. Unlike the previous open chamber cartridge, this version shows the symmetrical tround shape, which would facilitate feeding from a magazine, since the trounds can enter the split in any orientation and end up seating correctly. This reduced the complexity and cost of the open chamber firearm design, making it feasible for commercial production. The trounds were constructed of either high strength plastic or aluminum to provide strength^[1]. While commercial trounds were only available cartridges suitable for handguns, prototype military trounds were made in larger calibers. This article or section does not cite any references or sources. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... A Browning 9 millimeter Hi-Power Ordnance pistol of the French Navy, 19th century, using a Percussion cap mechanism Derringers were small and easily hidden. ...

Tround adapters

While trounds could be complete firearms cartridges, many trounds were made as chamber adapters which held a standard cartridge, such as a .38 Special^[2]. This allowed readily available ammunition to be loaded into the trounds and fired from Dardick's guns. The .22 caliber tround held standard rimfire ammunition, and the guns that could fire it were equipped with a selectable firing pin to handle centerfire trounds or trounds loaded with rimfire cartridges. A 32 ACP FMJ cartridge, a 32 ACP FMJ cartridge in a blued . ... Left to right: .38 Special, .17 HMR and . ... A rimfire is a type of firearm cartridge. ... The firing pin is a very hard steel rod with a one small, rounded end for striking the primer of a cartridge. ... A centerfire cartridge is a cartridge in which the primer is located in the center of the cartridge case head. ...

SALVO trounds

Patent drawing of SALVO tround

Dardick's patent 3,855,931, issued in 1974, expands the tround to hold multiple projectiles, firing through a set of barrels (one per projectile), making a Project SALVO type gun. This type of tround, holding three projectiles, was used in the H & R Firearms SPIW prototype. However it was rejected due to issues with weight (due to the three barrels) and strength of the tround when used with the high velocity flechette ammunition^[3]. Early Springfield Armory SPIW prototype (Circa 1964) Final Springfield Armory SPIW prototype (Circa 1966) The Special Purpose Individual Weapon (SPIW) was a long-running US Army program to develop, in part, a workable flechette-based rifle, though other concepts were also involved. ... H & R Firearms is a Marlin Firearms-owned manufacturer of firearms, especially single-shot shotguns . ... The Special Purpose Individual Weapon (SPIW) was a long-running US Army program to develop a workable flechette based rifle. Developed primarily by Irwin Barr, one of the founders of AAI (Aircraft Armaments Inc. ... The word flechette is French and means dart (literally, little arrow). It is a projectile having the form of a small metal dart, usually steel, with a sharp-pointed tip and a tail with several vanes to stabilize it during flight. ...

Tround Terra-drill

Patent drawing of Terra-drill

The Tround Terra-drill is described in patent 4,004,642, issued to Dardick in 1977. The Terra-drill is a drill head that combines a traditional drill bit with the SALVO tround . The tround is used to break through hard spots that the drill bit cannot readily penetrate. This version uses four ceramic bullets, which shatter upon impacting the rock, and which in turn are intended to fracture the rock to allow the drill bit to proceed. The tround is designed such that each projectile impacts the target at a slightly different time, imparting multiple shocks to create constructive interference of the shock waves in the target material. Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικός (keramikos). ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...

Dardick firearms

The Dardick firearms were basically revolvers whose unique open chambers could be reloaded from a magazine. The operating principle used was the same as a double action revolver, with a long trigger pull serving to rotate the cylinder, cock, and release the hammer. Since the commercial trounds had the same exterior dimensions, the same firearm action would, by using a different barrel, chamber any of the calibers the trounds were chambered in. rEVOLVEr (2004) is the fourth studio album release by Swedish thrash metal band The Haunted. ... Gravure of a 30-round STANAG 4179 magazine, originally designed for the AR-15/M16 series of rifles. ... The term double action was originally applied to revolvers. ...

The Dardick Model 1100 had a 10 tround magazine, and was only available chambered in .38 Dardick Tround (9 mm)^[4]. The Model 1500 came with interchangeable barrels, and was available in .38 (9 mm), .30 (7.62 mm), and .22 (5.56 mm) trounds, with a carbine conversion kit also available in .38 and .22. The Model 1500 could be configured to hold 11 or 15 rounds, and came with 4 or 6 inch barrel lengths.^[5] A Model 2000 with a 20 round capacity is also reported to exist. All versions used a non-removable magazine, which could be loaded with stripper clips or one round at a time^[6] A carbine is a firearm similar to, but generally shorter and less powerful than, a rifle or musket of a given period. ... A stripper clip or charger, not to be confused with the revolver clip or plain clip, is a speedloader that holds several cartridges together in a single unit for easier loading of a firearms magazine. ...

References

1. ^ http://rtbltd.com/arch/cats/1203_08.pdf
2. ^ http://www.thedonovan.com/archives/002987.html
3. ^ Special Purpose Individual Weapons at The Gun Zone
4. ^ Blue Book of Gun Values, 13th Ed. S. P. Fjestad, p. 339
5. ^ Numrich Gun Parts Corp. exploded parts photo of the Dardick Model 1500
6. ^ http://blogonomicon.eponym.com/blog/_archives/2006/8/21/2251122.html

External links

• Picture of Model 1500 pistol
• Diagram of Dardick's open chamber design
• Picture of a tround with other cartridges for comparison