This was done in late 2003 or early 2004, when the M118LR nominal change was lowered to 43.1 gr. of RE-15 from 44.3 gr. of that powder. This is the nominal load, assuming use of canister grade powder; however, most lots disassembled show an actual powder charge of about 42.8 grains of RE-15. The result was a 40 fps reduction in the velocity at 78 feet to around 2659 fps, which correlates to a 2,709 fps velocity from the 24″ barrel of the M24 or M40 rifle. Out of an M14, the muzzle velocity will be around 2685 fps. This load, though slower than the earlier lots of M118LR, can be used in the M14 with minimal risk to the rifle or gas system and it is this cartridge that is intended to be used with both the Army and Marines new M14 based EBR/EMR and M110 rifles.
Although this cartridge remains the current M118LR standard, it apparently still suffers from excessive velocity variation as the temperature changes and less accuracy than might be desired for truly precise shots at mid-range to long-range distances. The specification for M118LR requires 14 shots in less than 8 inches at 600 yards. To correct that difficulty, in 2008 the SOCOM/Navy sponsored a new developmental project to enhance the accuracy of the M118LR cartridge while maintaining its suitability for use in the M14, SR25 and M700 Remington rifle designs. As such port pressure consistency was a primary concern. The contract was given the Federal Cartridge Company, which for a long time has made a series of match cartridges under the “Gold Medal” brand. These were developed from the custom loads designed for the Marine Corp MTU in the 1970s (the IMR 3031 39 gr. match load). By this time IMR 4064 was the powder of preference for the Gold Medal match cartridge line. One of the areas considered by Federal Cartridge Co. was the case itself, with a more uniform neck concentricity tolerance than Lake City brass and beefed up web to cartridge case head interface being part of the finished cartridge design.
The result, when it was standardized as the MK316 Mod 0 cartridge, was a Federal modified case (Drawing number 8347636), Federal match primer, Sierra 175 grain Matchking and 41.75 grains of IMR 4064 powder. According to the published sources this load will produce a muzzle velocity of 2640 fps out of a 24 inch barrel. The load as produced by Federal is claimed to produce under 1 MOA out to 1000 yards from an appropriate rifle. With the IMR powder the shift in velocity is only 20 fps from 0 to 100 Deg C, with the Standard deviation in velocity over 40 rounds being 15 fps or less. In contrast the M118LR loaded with RE-15 powder will see a 50 fps rise in velocity for a 50 deg rise in temperature.
The MK316 ammunition is essentially the finest possible mass produced match ammunition, comparable to the hand loads utilized by the various service MTUs. The cost is higher than M118LR, with a government cost of 78 cents per round for the MK 316 Mod 0 rather than 55 cents for the M118LR (2009 prices).
In 2009 the NRA allowed the AR-10/SR-25 to be used as a service rifle for NRA competitions, which includes the Palma and 1000 yard matches. While the AR-10 was capable of exceedingly high accuracy, the 20 inch barrel put a further constraint on achievable velocities so crucial to 1000 yard performance. By this time the less than ideal transonic performance of the Sierra 175 gr. Match King had been shown by the performance of the M118LR cartridge fired from the AR10 rifle when these rifles were utilized in 1000 yard matches. In high winds the M118 LR cartridges show poor performance once the velocity drops below 1226 fps; therefore, performance on the 900 and 1000 yard lines can be problematic in high winds as the 20″ barrel of the AR10 simply does not generate the muzzle velocity needed to keep the 175 gr. Sierra above that threshold. Something new was needed to make the AR-10 with its 20″ barrel competitive in 1000 yard matches.
By German Salazars Rifleman's Journal