Elbonia has decided on the .408 CT for machine guns, so the question is now what machine gun to procure. The options considered by the procurement office so far are

• MG3 adapted to the calibre (somebody fell in love with the dotrine of high ROF)
• Short recoil MG, similar to LWMMG, scaled up
• Constant recoil for improved accuracy (might be too heavy)

the latter two options are considered preferable for light/dismounted infantry.

together with some optics (what kind of)?

Constant recoil would need a receiver like 2' long probably given the length we see for 7.62:

Is this a problem? What I am wondering about is weight compared to short recoil

graylion said:

Elbonia has decided on the .408 CT for machine guns, so the question is now what machine gun to procure.

You will need a quick change barrel feature for sure, as the .408 CT is perfectly able to make a smooth bore barrel of any rifled tubes with less than 1,000 rounds, in a bolt action rifle.

For MG use, you can probably expect a barrel life around ~500 rds.

Light weight version of Kord is the closest you could probably get off the shelf. But Case is closer to a stretched .338LM than 50BMG so custom gun is needed

EmericD said:

You will need a quick change barrel feature for sure, as the .408 CT is perfectly able to make a smooth bore barrel of any rifled tubes with less than 1,000 rounds, in a bolt action rifle.

Absolutely

MG3 action, 45x benchrest scope, because it needs a proper optic to take advantage of superior range and accuracy.

So what is which gun used for?

• 6.8x51 SAW
• 10.36x77 HMG for
  • dismounted use
  • distributing around camps
  • mounting for pintle mounts (do we want these at all?)
• 30x113 for all RWS
  • or do we want a version that is gas powered and mechanical striker for pintle mounting and camps?

If Elbonia was smart enough to cut a deal with France to have you as an advisor (paying you handsomely in the process, of course), what calibre should their medium machine gun use?

You mention 408CT is a barrel burner. Why?

If you take your most basic barrel burner excel file, which is a very rudimentary and meant to roughly indicate barrel life for a sporting rifle barrel, not a machine gun 

Given the same powder energy density and pressures, pure bore size to powder burn .408CT would be less of a barrel burner than 50bmg if it used similar bullets and similar pressures but 50bmg is typicaly at lower pressures.

Barrel burner rough comparison bore vs powder charge = barrel burned out

.50BMG   - .510     240gr    =  778rds

.408CT    -  .408      150gr   = 816 rds 

338 LM    - .338   100gr      = 865rds

.338 NM  - .338     90gr      =1069rds

.308Win  -    .308    47gr     =2700rds

.223Rem    -.224     24gr     =2896rds

300BLK      - .308     24gr     =10.365rds