Castle is often an underestimated operator in Siege, but when used correctly he can be extremely useful.
UMP-45: The UMP is an SMG with a decent fire rate, and medium to high damage output. The UMP is best for short accurate bursts (upwards of the head) to take out an enemy.
M1014: The M1014 is a standard shotgun that can be used to efficiently hold tight corners or spaces.
57USG: The 57USG is Castle’s standard pistol, with above average fire rate and medium damage.
M45-MEUSOC: The M45-MEUSOC is a more heavy-weight pistol than the 57USG, and can bear more power at the sacrifice of fire rate and some accuracy.
IMPACT GRENADE: Impact grenades are great for dealing some really fast damage on an area, and opening up holes in between sites or just for lines of sight.
DEPLOYABLE SHIELD: A deployable shield is a great tool for Castle, especially due to your ability to “shield trick” a reinforced castle door. (See tips section)
Note that my personal preference leans away from ACOG sights, as I tend to get close to the enemy, and ACOG is very disorienting at close ranges.
UMP-45: Holographic Sight, Verticle Grip, NO LASER SIGHT, and Flash Hider
57USG: Muzzle Brake
DEPLOYABLE SHIELD: I use the deployable shield either as you would normally, or to shield trick doors. (see tips section)
Shield tricking doors may be a viable strategy. Shield tricking a door is when you place a shield just far enough away from the outside of a door frame that you may still reinforce the doorway with a castle reinforcement. This means that when attackers attempt to get in, it is far more difficult (assuming they do not have an Ash) for them to hit the door, and to get inside overall.
Remember that if a teammate breaks down one of your barricades, you will be able to replace it.
Do not reinforce any doors until your team has gotten where they need to go, otherwise, they will simply break them down and you will have wasted your time.
WATCH OUT FOR FUZE – Fuze can place his cluster charge on any of your reinforcements, and you won’t be able to shoot him. Fuze will have a load of fun blowing the entirety of the room to hell.
Keep in mind that you can’t shoot through your reinforcements, and the enemy cannot either.
Your reinforcements take 12 hits to break down.
Try Castle tricking. This means that you may reinforce something (say a window for example, because this may easily stop a Fuze assault), and then hit the reinforcement 11 times. Then, if you hear a Fuze placing a cluster charge (or any other noise outside of the reinforcement), you may hit the reinforcement once, and start shooting as it falls to the ground, surprising the enemy.
Mute and castle are a brilliant combination to their amazing stopping power with his reinforcements. A thatcher or shock drone would be required to easily get through his doors if done correctly.
Don’t worry too much about someone placing a cluster charge on a window in a hostage room, it won’t work out well for them.