Looking for CR advice

[Yeoman]

I'm working on an intelligent construct character for my world and I was wondering what it's CR should be. Any and all help would be appreciated.

Thanks!

Iron Sentinel
Medium Construct
Hit Dice: 4d10 (22 hp)
Initiative: +0 (Dex)
Speed: 30 ft. (can’t run)
AC: 21 (+6 Natural, +5 Breastplate)
Attacks: Ierlan Heavy Spear +5 melee, or Luna Rifle +3 ranged
Damage: Ierlan Heavy Spear 1d10+3, or Luna Rifle 1d8
Face/Reach: 5 ft. by 5 ft./5 ft.
Special Attacks: N/A
Special Qualities: Construct, Damage Reduction 5/+1, Rust Vulnerability, Vulnerable to Mind Influencing Effects
Saves: Fort +1, Ref +1, Will +1
Abilities: Str 15, Dex 11, Con -, Int 13, Wis 10, Cha 8
Climate/Terrain: Ierlan Ruins
Organization: Solitary, Patrol (2-4), Squad (5-9)
Challenge Rating: 3-4?
Treasure: Ammunition (20 .35 Caliber Bullets), Luna Rifle, Ierlan Heavy Spear, Breastplate
Alignment: Always Lawful Neutral
Advancement: By Class

Abilities
Iron Sentinels do not need to breathe.

Construct: Immune to poison, disease, and similar effects. Not subject to critical hits, subdual damage, ability damage, energy drain, or death
from massive damage.

Mind Influencing Vulnerability (Ex): As sentient creatures, Iron Sentinels are vulnerable to mind influencing effects.

Rust Vulnerability (Ex): An Iron Sentinel is affected normally by rust attacks, such as that of a rust monster or a rusting grasp spell.

Favored Class: Fighter.

 

[The Serge]

I came out with CR 2.

It could have been higher if not for the mind-influencing effects (I generally count traits as 2, but since you took out a major benefit to the Construct traits, I counted it as 1).

However, you could argue for CR 3.

 

[Yeoman]

I was guessing 3, but I try to be pretty conservative in my estimates. I wasn't entirely sure of how much the rest of the construct "package" would be worth CR wise. Now from a different standpoint, what kind of Level Adjustment would we be looking at? I'm thinking in the 2 or 3 range, leading to an ECL of 6-7.

Thanks!

 

[The Serge]

That sounds about right... Heck, it may even be lower because it's saves are pretty poor.

Compare the creature to a 6th level Fighter and see which one you'd rather play from a min/max perspective.

 

[Yeoman]

Cool, thanks for the assistance!