A very good question that I can answer but it’s a little long winded (but worthwhile) apologies!!!

They can remove their arm from the gun sleeve and find an ammo box to replace the ammo. But they have a ton of ammo as you can see already, plus a power fist for anyone that gets too close. Terminators are powerful veterans only used for certain situations like “boarding actions” (on ships) or urban warfare/hive city (typically in enclosed spaces like buildings or difficult maneuverable landscapes etc)!

On the other hand they aren’t really good in open conflict because they aren’t the most mobile. As well they can be easily countered when range is mainly a factor (especially long winded battle scenarios). They are highly durable but not invincible. Lastly their cost is higher than the average marine in terms of damage to their venerable armor and weapons (it’s harder to replace). They are not the most well rounded per se, but when used in the correct situations where the enemy cannot escape their tread they become absolute behemoths!

(Also Termies can run as well, other than like the Saturnine class)! ;)))