Perhaps you can explain this, then:
Would you like more examples of longer barrels?
Fact is, longer barrels are quite frequently used for "general military issue" for the purpose of greater accuracy at long range despite their increased weight, and not just for "bling".
The trend in military arms has been smaller and lighter. In caliber and barrel length. This starts about the same time as the Advent of Smokeless powder.
The SCAR H sorta bucks that trend but it did so as the US was fighting in Afghanistan where mountains changed the rules a bit. Fighting from the side of a mountain to the side of a mountain or across a very long field calls for a bit more range.
The version you point to is the SCAR H which is generally chambered for the 7.62x51mm NATO. That round was basically a 1950s era reduced weight version of the 30.06 round used in American m1 Garand rifles in world war 2. It's a full power higher caliber battle rifle round. Intended to offer longer reach (around 800m) then a conventional infantry rifle which is optimized for fighting in side about 500 meters
As such it demands a longer barrel to achieve proper powder burn vs the true intermediate calibers like the 7.62x39mm, 5.56x45mm, 5.8x42mm,5.45x39mm.
But Iron man compare the barrel length of the Mk 17 and Mk20 SCAR H to the G3, FAL, M14, and M1 Garand and PSG1.
The oldest on the list is the M1 Garand. Which as I stated fires the 30.06 caliber. Why is it even here? a 24 inch barrel. So? This is the second longest barrel of my little list. and it's the oldest. This length came from the Springfield M1903 rifle used from the First world war until about Vietnam when the US finally phased them out of the Sniper rifle role. It was the offical Rifle of the US from the start of world war 2 till 1959 but was not that widely used by the US after VJ Day the preference for the Korean war being the M1/M2 Carbine with an 18 inch barrel.
The M14 now comes in chambered again for the reduced weight and sized cartridge based off the 30.06 the 7.62x51mm. M14 started off when the US Army tried to get a detachable magazine version of the M1. As the project progressed they wanted to try and keep the Machining and some backwards compatibility with the M1 but the End product had to drop that. the M14 has a 22 inch barrel. Ah ha you say! but then I point out that although M14 has served in the US Military since 1959, it only actually was used as the main service rifle for all of 5 years as in 1964 the M16 replaced it and Early M16s had a very thin 20 inch barrel. The M16 it's self has more or less been replaced by the M4 (14.5 inch barrel) and M27 (16.5 inch barrel) in US service. The Italians replaced theirs with AR70/90 soon to be Replaced ARX160 (16 inch)
The US retained M14 as a DMR rifle and in the post 9/11 world rebuilt them in a more modern form replacing the barrels with either a 22 inch barrel or a 18 inch barrel. They are now being phased down in exchange for Mk11 or M110 rifles with a 20 inch barrel and soon for M110A1 with and M38 rifles (5.56x45mm USMC) both with 16.5 inch barrels.
FN FAL had a longer service rifle life then the M14. it was developed at the same time as the M14 and was in trails for the M14 Rifle.
It has a 21 inch barrel but as time went on and Production continued that length moved to 18, then 17 and modern commercial versions in 16 inch barreled versions.
FAL has been replaced by a large number of rifles all of which are 5.56x45mm with Shorter barrels French Famas(19.2 inch barrel but 24 inch DMR option) To be Replaced it's self by HK416 with a 14.5 inch barrel, British SA80 ( 20.4 inch barrel), Austrian AUG and it's own successor the FNC (17.7 inch), as well as adoption of the Mk16 SCAR L (16 inch) and AR variants as well as Tavor and Gailil rifles ranging from 20 inch barrels to 13 inch barrels.
Then we Hit the G3 series.G3 came at about the same time as the M14 and the FAL's adoption but is based on a a design of a late war German successor to the STG44. The main issue barrel length for the G3 is 17 inches. Making it the shortest of the Big 3 Western battle rifles. yet it has a couple variants here the Longest barrel on my little list is the PSG1 with a 25.6 inch barrel. And the MSG variants ( there are two MSG3 and MSG90) both with 23.6 inch barrels.
Victory? not yet. The MSG were Military DMR and Sniper rifles The German army in the Cold war didn't have a Doctrine for a dedicated sniper until post reunification. The PSG1 Is unique but not a military weapon it's a Police weapon. as such the length is a less critical issue.
G3 has been replaced in service mostly by either G36 or HK416 with 18.9 and 16.5 inch barrels in 5.56x45mm. The PSG1 and MSG1 were replaced mostly by the G28 a HK417 based 7.62x51mm rifle with a 16.5 inch barrel.
So where does the Mk20 come from?
The Idea with the Scar was to introduce a rifle family with a very high degree of commonality, Socom does't want to be spending all it's money on rifles after all. They get M4A1 by piggy backing off army orders to they basically get those for Free but the SCAR was out of there proverbial pocket. So one rifle to rule them all makes sense. At the Time Socom was starting to fight in Afghanistan and there were some QC issues with the M4 and how it was being used. this created the want to 2 rifles. add in Socom has been dreaming for a long time of a 7.62x39mm rifle with all the advantages of the M4A1 to boot and the SCAR requirements were begun. Although in Some ways the G3 series is the perfect forerunner of SOCOM's wishlist just lacking rails it also lacked the degree of modularity they wanted and AR familiarity. They wanted all versions to be available in 3 sizes, Short barrel for close quarters and PDW work, a carbine length for standard issue and a long barrel for DMR work.
as the Program was getting up and running 2 families emerged the Mk16 in 5.56x45 the Mk17 in 7.62x51 the latter eventually developed a 7.62x39mm conversion kit but that's about as common as a Unicorn owned by a Leprechaun living in Shangri La.
Mk 16 was supposed to be the Socom universal rifle for 5.56 well Mk 17 the universal rifle for 7.62. If you need a weapon that doesn't use these calibers well then you are basically you would get something specialized anyway.
Mk 16 scar and Mk 17 scar entered trails with Socom but the Mk 16 was dropped from US use. Around the Same time the M4A1 has undergone modifications and the issues Socom had were fixed so why buy a 5.56mm rifle when they could get them for free M4A1 returned as the "Universal" 5.56 of socom also around this time Socom basically decided not to bother with a 5.56x45mm DMR after all they had the SCAR H for that. This left SCAR H the Mk 17 the 13 inch barrel version originally to be the CQB version became the defacto standard issue. The 16 inch barrel version became more the DMR, And Socom rethought the long barreled 20 inch. See Socom was more or less looking to drop 7.62x51mm from it's bolt action line up. Socom like the Army and Marines were realizing that in the Sniper role they were getting demising returns from the 7.62x51mm compared to .300WM or .338LM/Norma and the newer bolt guns could be reconfigured to shoot any of those.
The Mk 20 Emerged as more of a 7.62x51mm Semi automatic Sniper rifle, the Name attached by FN Sniper support Rifle is in direct reference to this.
The Idea is that the Sniper with a Bolt action or a Anti material rifle is kinda tied down. If they are taking a long range shot then fine but if they suddenly find themselves under assault a Bolt action is basically useless and there fall back is a sidearm. fortunately Sniper teams are 2 people. Old school was that the other member of the team would then bring a M16 with a M203 Grenade launcher. Someone realized that they have 2 trained snipers and yes you need a weapon more for closer range but why give up the long range? This is where SSR comes in. you give one the bolt gun the other the SSR. both can take long range shots, The Spotter can also assist by taking follow on or secondary targets or serve as a defensive weapon in a SF team it can also act as a DMR. the Semi auto nature allows for faster follow on shots and engagement despite "One shot One kill" you sometimes need that second shot or third shot and a semiauto is faster to that then a bolt.
