Add FS2000(plus STANAG mag volume update)

[ghost]

Summary

SUMMARY: Content "Add FS2000 as rare rifle, give STANAG magazine real volume"

Purpose of change

Redo of #36436.

Describe the solution

Due to the handguard being removable but not on a rail, it is being added as "factory handguard" and fits in the underbarrel mount slot. Thus, you'd still have to add a mount to use anything other than the handguard(which then locks out using it if the rail mount is added since it's irremovable).

Volume: Use the owner's manual's overall length for scaling in ImageJ on this image from the manual, multiply by width. Do again after erasing handguards from image to get handguardless volume. Use difference as factory handguard mod's volume(568ml).

Additional image of trirail version for basis of trigger guard size on handguardless edit:

Results for surface area:

Weight: Take from manual for gun w/ handguard. To generize the handguard for any other guns that come with those by default, take average of Magpull's handguard selection.

Frequency: Tonkatsu's Gunbroker Method™ using guns_rifles_rare

Describe alternatives you've considered

Not adding it.

Testing

Started game for load errors, went to gun stores to see if spawning.

Additional context

The volume being comparatively huge to other rifles and holsters is a relic of bad scaling on the other rifles from the n*250ml era of modeling.
Tuna power!

[I-am-Erk]

I'm putting a feature freeze on this that can be removed once the generic guns update is merged so this can be made compliant with it.

[tenmillimaster]

You can shave a few more mL off by deleting the magazine from your picture.

Also this ejects tamely enough-maybe it can 'catch brass' by default?

[tenmillimaster]

Looks quite good.

[SirPendrak]

Bullpup should not have stock mount slot

[ghost]

GunBroker prevalance math:

Taking average of the hypothetical weights 1-20, with total number for M24/Remington 700.

Edit: Added semiauto G3s(count from 1&1semi->1&35 semis, used total of 36) per tenmillimaster's suggestion, weighting moved from 7 to 6.

[tenmillimaster]

Some suggested changes. Also a mispelling.

[ghost]

Ran Generic Guns test with FS2000 set to very high weighting so it would be the predominant drop, replaced with sporter carbine as expected. Handguard doesn't(nor is intended to) appear on the migrated rifle, so this should be good now.