.260 Remington

The .260 Remington (also known as 6.5-08 A-Square) cartridge was introduced by Remington in 1997. Many wildcat cartridges based on the .308 Winchester case had existed for years before Remington standardized this round. Although loaded to higher pressures, the ballistics of this cartridge are basically similar to the 6.5×55mm when bullet weights do not exceed 140 grains. When loaded with heavier bullets, the 6.5×55mm is capable of greater velocity. However, due to its shorter overall length, the .260 Remington has a slight advantage over the Swedish Mauser in that it can be chambered in a shorter length bolt action.

Because 6.5 mm (.264") bullets have relatively high ballistic coefficients, the .260 Remington has seen success in rifle competition. It is capable of duplicating the trajectory of the .300 Winchester Magnum while generating significantly lower recoil. Also, converting a rifle chambered for the .308 Winchester (or any of its offspring, such as the .243 Winchester, 7mm-08 Remington or .338 Federal) to .260 Remington generally requires little more than a simple barrel change.

Origin & History
Remington has had a track record of adopting successful wildcat cartridges into the Remington fold by offering rifles and ammunition and at times attaching their name to the cartridge. Like many cartridges such as the .22–250 Remington, .25-06 Remington and the 7 mm-08 Remington, the .260 Remington started its life as a wildcat cartridge called the 6.5-08 and was eventually released as a commercial cartridge by Remington. However, it was not Remington who first attempted to standardize the cartridge. LTC Arthur Alphin and his company A-Square LLC submitted the first proposal and drawings to SAAMI for the standardization of the cartridge. Remington was to file similar papers with SAAMI to do the same a few months later. When the dust settled it was found that the 6.5-08 would be called the .260 Remington instead of 6.5–08 A-Square.

The 6.5 -08 cartridge was created simply by necking down the .308 Winchester or the 7 mm-08 Remington or necking up the .243 Winchester cartridge to create the case. Since all these cartridges had the same basic dimensions right up to the shoulder, case forming was a relatively simple task for anyone with an understanding of reloading and case forming. As the parent cartridges were readily available for low cost, the 6.5 -08 was often an economical alternative to cartridges such as the 6.5x55 Swedish Mauser. What the 6.5-08 provided over the .243 Winchester, .308 Winchester and to a lesser degree the 7 mm-08 Remington was bullets with excellent ballistic coefficients and sectional densities relative to their weights.

Since the 6.5-08 was a wildcat cartridge, there were variations between cartridge chambers depending on the reamer used to cut the chamber. Furthermore depending on whether one chose to form the case from .243 Winchester or .308 Winchester influenced the neck thickness and therefore the dimensions of the cartridge. A cartridge formed for a specific rifle may or may not successfully chamber or worse may reach dangerous pressures in another. Standardizing the cartridge served the purpose of providing design specifications for the cartridge so as to address the issues the cartridge experienced as a wildcat cartridge.

.264 caliber (6.5 mm) caliber has historically been unsuccessful in North America but has been one of the mainstays in Europe especially in the Scandinavian countries. The 6.5x54 Mannlicher-Schoenauer, 6.5x55 Swedish Mauser, 6.5x57 Mauser 6.5-284 Norma have loyal followings in Europe. Starting with the .264 Winchester Magnum and later the 6.5 Remington Magnum North American cartridges in this caliber have been largely failures. The .260 Remington appeared to be following this North American trend, with Remington only producing the Model Seven Synthetic in the .260 Remington for 2011 as it has discontinued such rifles as the Model 700 CDL and the Model Seven (including the youth model) in the .260 Remington. However, Remington continues to manufacture several types of loaded ammunition for .260 Remington. The use of the .260 Remington by SGT Sherri Gallagher to win the 2010 NRA High Power National Championship has sparked a resurgence in the round, and Lapua announced at the 2011 SHOT show that it would be manufacturing .260 Remington brass.

Design & Specifications
The .260 Remington uses the .308 Winchester case as its parent cartridge which is simply necked down to accept a .264 caliber bullet with no further changes made to the case. As the cartridge follows a modern design, it has little taper which allowed its parent cartridge to feed reliably through auto-loading rifles such as the M-14, FN-FAL and the H&K G3. The .260 Remington has a case capacity of about 3.47 ml (53.5 grains) H2O.

Both SAAMI and C.I.P. have provided design specifications for the .260 Remington cartridge. While there are minor dimensional differences between dimensions provided by both organizations, these dimensional differences mostly fall within the tolerances allowed by the other organization, though C.I.P. lists the .260 as a Delta L problem cartridge. SAAMI dimensions for the cartridge were issued on January 29, 1999 when the Remington’s submission was accepted.

SAAMI specifications

 * [[Image:260Remington.png|450px|alt=260 Remington Schematic|.260 Remington schematic diagram conforming to SAAMI dimensions|.260 Remington schematic complying with SAAMI specifications.]]
 * .260 Remington SAAMI compliant schematic. All dimensions in inches [millimeters].

SAAMI recommends a barrel with a 6 groove contour and a twist rate of one revolution every 9 in with each groove having a width of .095 in. The recommended bore diameter is .256 in and the groove diameter is .264 in. The SAAMI recommends that rifling commence at .2209 in from the chamber mouth. SAAMI recommends a pressure of 60000 psi

C.I.P. specifications


.260 Remington maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm) plus Imperial (inches).

Americans would define the shoulder angle at alpha/2 = 20 degrees. The common rifling twist rate for this cartridge is 229 mm (1 in 9 in), 6 grooves, Ø lands = 6.50 mm, Ø grooves = 6.71 mm, land width = 2.42 mm and the primer type is large rifle.

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) guidelines the .260 Remington case can handle up to 415 MPa (60,190 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.

Performance
The .260 Remington being a .264 caliber (6.5 mm) has certain advantages: sectional density and bullets of good weights. Factory ammunition usually are loaded with bullets weighting anywhere from 120 gr to 140 gr. Bullets available to the reloader range from 90 gr to 160 gr. The 120 gr bullet has a sectional density of 0.246 which is similar to a 165 gr .308 caliber (7.62 mm) bullet. The 140 gr bullet has a sectional density of 0.287 which is similar to that of a 190 gr .308 caliber (7.62 mm) bullet. The 160 gr bullet which has a sectional density of 0.328 is similar in sectional density to a 220 gr .308 caliber (7.62 mm) bullet. As sectional density plays a large factor in penetration, the .264 caliber (6.5 mm), though a diminutive caliber from a North American point of view, has had excellent results in the field. Walter D.M. Bell who was known to have shot over a thousand elephants in his lifetime used, among others, .264 caliber (6.5 mm) and .284 caliber (7 mm) rifles to do so.

The .260 Remington while having a slightly lesser case capacity than the 6.5x55 Swedish Mauser, is loaded to higher pressure levels. This fact has allowed the .260 Remington to outperform the Swede as far as factory manufactured ammunition is concerned. Typically, the .260 Remington is loaded with a 120 gr bullet at 2890 ft/s and the 140 gr bullet at 2750 ft/s. In contrast the Norma of Sweden loads the 6.5x55 SE with a 120 gr bullet at 2822 ft/s and the 140 gr bullet at 2690 ft/s.

While it is possible to load the 160 gr bullet which is popular in Northern Europe, for the .260 Remington, due to the comparatively short overall length of the cartridge, the bullet will need to be seated deep into the body of the cartridge displacing space which could be taken up by the propellant. For this reason, bullets weighing over 140 gr are not generally recommended for loading with this cartridge.

Sporting Usage
Due in large part to its parentage, the .260 Remington has been adopted into tactical and target shooting rifle platforms. Any rifle which is chambered for the 7.62x51 NATO or the .308 Winchester can be converted with only the addition of an appropriate barrel to the .260 Remington. Companies such as Armalite (AR-10), DPMS Panther Arms, Tubbs and KMW are among several companies which currently manufacture tactical rifles for use with this cartridge. As the 6.5 mm (.264 caliber) bullets are known for their excellent ballistic coefficients, it is little wonder that they have been adopted for target shooting especially by the Scandinavian nations. Tubbs manufactures rifles for competition one of which went on to win the NRA HP Championship in 2010.

The .260 Remington has been found effective against large deer species such as elk and moose, but some hunters, particularly Canadian professional hunters who hunt large moose and elk, consider it slightly underpowered for these species and best used for smaller deer species such as white-tail and mule deer. However, the 6.5×55mm, which is usually loaded to a lower power level than the .260 Remington, is commonly used in Norway and Sweden with bullets weighing at least 9 g to kill Eurasian elk (a term which is applied to moose in these countries). The .260 Remington would make an excellent cartridge for hunting smaller African antelopes weighting 440 lb or less.

Loaded with lighter bullets, the .260 Remington can be used as an effective varmint or a small predator hunting cartridge for use against such species as marmots, woodchucks, bobcats and coyotes. Bullets chosen for these species should be designed to open rapidly unless harvesting of the pelt is the objective. FMJ or other non-expanding bullets can be used if the latter is the case.

Rifles & Ammunition
When the .260 Remington was introduced, Remington chambered the cartridge in both the Model 700 (BDL and CDL) and the Model Seven (CDL and Youth) rifles. Remington also offered the cartridge in a Law Enforcement (LE) only model of the Model 700 rifle. However, Remington has discontinued the chambering of the .260 Remington in these models. However, the Remington Custom Shop continues to produce rifles chambered for the cartridge.

Browning at one time chambered the cartridge in their copy of the Winchester 1885 Low Wall rifle which Browning markets as the B78 and also their A-Bolt Micro Hunter rifle. Browning has since discontinued the .260 Remington chambering in these models.

Savage Arms continues to manufacture several rifles chambered for the .260 Remington. Currently they offer the Hunter Series 11 FCNS, Weather Warrior Series 16 FCSS, and the Target Series Model 12Long Range Precision rifle. Savage also chambers the cartridge in more specialized rifles such as the Model 10 Predator Hunter Max 1, Model 11 Lightweight Hunter and the Model 11 Long Range Hunter.

Controversy
The cartridge that is now popularly known as the .260 Remington was submitted for standardization under SAAMI by the A-Square Company in 1996, several months prior to Remington announcing their plans to introduce the cartridge under their own name. A-Square's submission was called the 6.5-08 A-Square. Some users continue to refer to the cartridge under this name.

Since the acceptance of the submission by Remington Arms for the standardization of the 6.5-08 cartridge by SAAMI, A-Square has dropped the cartridge from their line of cartridges chambered for their rifles and no longer offers ammunition in this cartridge. Instead A-Square LLC has gone on to produce rifles and ammunition for the 6.5-06 A-Square cartridge which is based on the .30-03 Springfield (via the .30-06 Springfield) necked down to .264 caliber (6.5 mm). This cartridge provides over a 200 ft/s velocity advantage over the .260 Remington.