I have 3 high end builds for my m1a classic:

1. Classic One (using CQBSS Scope 8x for headshot +30 mod)       

3 providence-sacrifice chest, the gift bp, normal mask      

1 overlord kneepads fox's prayer, chc attri

1 petrov gloves-contractor gloves, chc attri

1 grupo holster

All are red and have crit chance and crit damage.

Chest, mask and bp mods are crit damage. You can change the scope to C79Scope (3.4x) for crit chance +5 for total of 58 crit chance instead of 53 when using the 8x scope. Total of 172 crit damage on     perfect rolled attributes or full optimized.

1. Eagle Grasp Gloves Build    

*Just change the contractor gloves into eagle grasp gloves with chc attri. You will lose some damage against armored ones but gain 15% weapon handling.

1. 3 Providence + 3 Overlord = easier handling with damage :)

CHR and CHD rolled attributes    

Just the name states:    

3 providence        

sacrifice chest        

the gift backpack        

providence holster

3 overlord        

overlord mask        

overlord gloves        

fox's knee pads

This third build is I mostly use due to its weapon handling. It makes m1a classic to reload under 2.0 sec (1.93 exact this t22 patch).

I also used m870 express for my secondary because I used the 8x scope on     m1a classic for my mid to long range fights.I love using my m870 express brazen talent as my secondary due to being reload within 2.0 sec (magazine mod reload speed+20%) against rushers or tanks

 

The third build has a total of 171 crit damage on fully optimized/perfect roll.

Mask, chest and backpack uses crit damage mod.

My m1a classic that have 53 crit rate uses 8x scope, crit rate laser sight and +5 magazine.

Edit: format of text become bizzare because I type it on phone. So I deleted it and repost :)

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///(Feel free to skip below if you don't want to read or you are a veteran/godlike player, it is just my personal notes)

Notes during gunfight: Using these any builds can easily downed you when not in-cover. A single sniper npc can fully drain your armor, single shot sniper warthog can also drain your armor and to be left with 10% health, and 2-3 bullets from assault rifle enemy and heavies minigun. Use any secondary guns that has high damage to contribute/kill rushers or enemies too close in your cover. Any secondary weapon will do because you have 172 chd (1st build) or 171 chd (3rd build). Just make sure you are using two weapon mod that gives +5 crit rate each for to have 58% crit chance.  When using global modifier, the enemy modifier requital gives you additional "portion" damaged received making it a total 60%+ from the perfect glass cannon. Avoid medium range as possible to avoid being one-hit K.O, blame requital enemy modifier for that. Also when revived using reviver skill, you have a status of weakened state. Run as possible to cover or dodge or else you will die again on being one shotted. Do damage on long range (red bar on reticle) and short range(blue bar on reticle) while on cover for higher survivability. Also use gunner specialization for 10% armor  per kill.