An idea that was popular in the military press sometime back was for infantry squads and platoons to have organic snipers. Or, looked at another way, the best shot in a squad should be given equipment to exploit his talent. According to FM 100-60 and 100-63 many Russian units already incorporate a SVD rifleman. This man will also be armed with an AK-74 and carried whichever weapon was appropriate for the action.
The name most often used for a squad level sniper is "Designated Marksman". Terms such as "Sharpshooter" and "Chosen Man" also have historical precedents. The envisioned role for the DM is that while machine guns are used to suppress the area an enemy is in, the DM engages any point targets that present themselves, priority being given to leaders, heavy weapons and electronic equipment (radios, designators etc). Its probable that the DM will be issued with AP, AP-Incendiary or Sabotted ammunition. There are several options for arming such a man. It is likely that the weapon used will be in a chambering compatible with rounds used in the squad's rifles or machine guns, at least at squad level. I've come across reports that the British Army is using .338 rifles at platoon level for units in the JRRF (Joint Rapid Reaction Force) on the basis of 14 per battalion, with one per platoon and a small pool for snipers in the battalion recce platoons.
Option one is for him to use a scope equipped assault rifle. This weapon may also have a heavier barrel and a bipod. In some cases the difference between a sniping weapon and a scoped SAW is more one of application than form. Russian RPK gunners who were equipped with scopes commented that they could now shoot as accurately as snipers. It may be in some units the DM is also a SAW gunner. This is probably the best option for a Squad-level marksman.
Option two is to arm him with a medium weight bolt action weapon such as the L42A1. Some commercial hunting rifles may be suitable "off the shelf". Bolt actions still have the advantage over self loaders in certain contexts such as suppressed firing. Good features of the L42A1 are iron sights and a fast Lee action. A squad-level sniper will often operate in close proximity to the enemy and it may be felt that a bolt-action weapon lacks sufficient self-protection capability.
Option three is to equip the DM with a scoped 7.62x51mm Battle rifle. This gives the DM longer range and hitting power while offering better defensive firepower. US forces will probably adopt M16 based weapon such as the Stoner SR-25 or AR-10B. British and German forces will probably opt for the FAL and G3, which some serving personnel will still be familiar with. It has been suggested that this rifle be heavy barreled and have burst fire or even full automatic mode available. While there is some merit in having a weapon that can punch a three round burst through a truck's windscreen, it is probably a mistake to try and make the 7.62mm DMR serve as a LMG. Like the M1918 BAR it will end up too heavy to be a rifle or too light to be a machine gun. The DMR's virtue is precision rather than volume. The capability to fire a high cyclic rate two or three round burst will improve long range hit probability if the rifle is sufficiently controllable.
Further Comments It's odd how terms change and evolve. When I first encountered the term "Designated Marksman Rifle" it was in the context above. Since then the term has begun to be used for a semi-automatic rifle to arm the Spotter in a sniper team. Recently DMR has changed context again
Now it is being used for a semi-automatic sniping rifle. The model above is essentially a M21 brought into the 21st century.
UPDATE "M16A4 with associated combat optic (ACOG 4x), the West Coast’s SAM Rifle ~ All interviewed were extremely pleased with the performance and felt it “answered the mail” for the role of the Squad Advanced Marksman (SAM). All said the fixed 4-power ACOG sight that was included was the perfect solution. It gave them the ability to identify targets at distance, under poor conditions, and maintained ability to quickly acquire the target in the close in (MOUT/room clearing) environment. As above, many “stacked” it with the AN/PVS-14 to get a true night capability. No Marines present in interviews knew of any situation where the shooter could shoot the gun to its full capability or outshoot it. Interviewees included STA platoon leadership and members who are school trained MOS 8541 Snipers. They saw no need for the accuracy and expense involved in the version being built for the “East Coast” SAM Rifle by Precision Weapons Section (PWS), WTBN, Quantico. The standard M16A4 with issued optic more than satisfied their requirements."
The above report illustrates that many off-the-shelf weapons may be sufficiently accurate to meet the needs of a Squad Marksman. The Israelis have choosen a scoped M-16 as a DMR, there being five marksmen in a platoon.
A good case can be made that the best choice of weapon for a Squad Marksman would be a semi-automatic or selective fire 7.62mm weapon, such a weapon giving the correct balance of long-range punch and defensive firepower. On the other hand a equally good case can be made for having a weapon that can use the same ammunition and magazines as the rest of the squad's weapons. Possibly the choice will boil down to personal preference and the terrain being operated in.
Further Update The British Army has recently began to issue the L110 (FN Minimi/M249) on a more general scale. What is interesting is that the L86 LSW will be retained. One suggestion that I've seen is that a fire team should have two riflemen, an LSW and a SAW. One of the rifles will probably have a 40mm Underbarrel Grenade Launcher. Even though based on weapons as poor as the SA-80 family, such an armament offers considerable firepower, obviously an advantage for small unit operations such as COIN. It is envisioned that the LSW have a dual role, supplementing the automatic fire of the SAW and providing long range precision fire to beyond the capabilities of the rifles. A M16 H-bar fitted with an ACOG sight will fill this role even more effectively, since its configuration allows the use of drums and C-mags.