Using the Editor as of dev build 0.53.103696:

1. Place a BLUFOR Marksman somewhere in Stratis.
2. Add to the Marksman's init: this addPrimaryWeaponItem "muzzle_snds_B"
3. Place a [BLUE] Basic Ammo box in front of the Marksman.
4. Click Preview, then once in the game world "aim" at the ammo box until the action menu option for "Inventory" is available and select that option.
5. Drag a "6.5mm 30Rnd STANAG Mag" from the crate tab into the MXM's magazine slot.
6. After the loading animation concludes, mouse over the 2D pictures of the MXM, the inserted magazine and the suppressor and read their tooltips.

ALTERNATELY

1. Place a unit somewhere in Stratis.
2. Add to the unit's init: removeAllWeapons this; this addMagazine "30Rnd_65x39_caseless_mag"; this addWeapon "arifle_MXM_f"; this addPrimaryWeaponItem "muzzle_snds_B"
3. Click Preview.
4. Press the Inventory key, then mouse over the weapon, its magazine and its muzzle accessory and read their tooltips.

ALTERNATELY

1. Place a Marksman somewhere in Stratis.
2. Add to the Marksman's init: this addPrimaryWeaponItem "muzzle_snds_B"
3. Click Preview.
4. Press the Inventory key, then and mouse over the weapon and its muzzle accessory and read their tooltips.

This issue was discovered while I was reproducing and verifying ticket ID # 0006667, "Wrong Ammunition marksman" ( http://feedback.arma3.com/view.php?id=6667 ).

The included screenshot is submitted as visual proof of this issue being reproduced using both of the alternate methods, as well as visual proof of ticket # 0006667.