So this is my first rodeo guys, so please don't flame too hard.  I'd rather ask than assume, even if it sounds like a stupid question.  I'm working on a pistol build and trying to set this thing up right.  Having decided on using an aftermarket trigger (the RA-140 has a price point and such fantastic reviews, it's hard to resist) I've read that there are various trigger retaining pins available for the AR platform. The 2 types that I've seen are anti-walk and anti-roll.  Now the names of these parts themselves makes the point of them obvious, though I'm still fuzzy on the benefits, having personally not heard of a rifle that has an issue of the trigger pins "walking" out of where they should be, and I sure don't get the benefit of preventing a cylindrical pin from just rolling forward and/or backward (though I'd think that if the pin is in there tight, it wouldn't roll in the first place).  Could somebody please shed some light on this for me so I can decide whether I even need to look at either of these solutions, and if so, which one and why.

Thanks!

You need anti walk/ rotation pins for the RA 140. On a standard mil spec trigger, the pins have spring tension on it. The tension prevents the pins from falling out, and I believe there's a J Spring in the hammer. In a drop in system, the pins aren't under any spring pressure. All anti rotation pins are anti walk, and usually have a bar, something connecting both pins. Some anti walk pins, don't prevent the pins from rotating, and are two separate pins, with screws. On a standard rifle, they aren't really needed because you're not going to get that  high of a round count for any damage to happen to the pin holes. Here is a cheap set of anti walk pins that'll do the job link

AR-15 XP BLACK OXIDE .154 ANTI WALK WITH NYLOCK PATCH, STAINLESS STEEL

AR-15 XP STAINLESS .154 ANTI WALK WITH THREAD LOCKING PATCH
Mil Spec Spring Groove Machined into Component.. Mil Spec Tolerances
Mil Spec Spring Groove Locks out Slop
Button Head machined into Pins on one end
Made in the USA by Xtreme Precision LLC
CNC Machined Stainless Steel…

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Welcome to ARFcom, OP!

You don't have to apologize for asking questions...just ask your question.  We all ask questions.  That's what we're here for.

So anti-walk and anti-roll pins are the same?  I was under the impression that they were different, though I had a feeling that anti-roll would also be anti-walk, but anti-walk would be just that...the market for the AR platform is so saturated with different features and gimmicy parts that it's sometimes difficult to tell what's useful, necessary, or just snake oil.  

endermend, that set of CMC pins looks pretty good, though labelled as just anti-walk.  Would those be adequate anti-roll pins as well?

PursuitSS, your experience with the RA-140 has definitely peaked my interest.  Do you have a link or those KNS pins that you like to use for your builds?

Hollywood_Shooter -- THANKS!  It's always a little frustrating being new to something relatively complicated with so many choices for so many different parts, but this forum really does look like it has just about all aspects of the AR platform covered.  

RockNRoll_Mullet, 3 questions....(1) would those both be anti-roll as well as anti-walk pins?  (2) what's the difference between these 2 sets of pins, and what would make one better or more ideal than the other?  (3) what's that conical piece in the first link that's not included with the second set?

Not sure what an "anti-roll" pin is.  Rolling about their axis, should it happen, would be a benign event.  Mil spec triggers and those that use the same pattern of attaching to the receiver all secure their trigger pin with the tail of the trigger spring.  The hammer pins are similarly secured by the little "j-spring" inside the hammer.  These pins don't drift out to the side under use, very reliable.  Cassette-type triggers are different, some means of securing the pins is necessary.  

I have a Velocity cassette trigger in one of my builds, it has a set screw in the bottom that puts pressure on the two pins so they don't drift sideways.  Not perfect, but with some threadlocker and enough torque it seems to be OK after several hundred rounds.  When in doubt, use the KNS pins which have a good reputation for security.  If either of these pins moves far enough laterally, the rifle is immediately disabled and needs some benchwork to return to service. - CW

The anti-walk pins can be bought cheaply (I've seen them for $8 somewhere) and if you take the time to take the length down on a bench stone so that the pin length is exactly the width of your receiver, they can also perform as anti-rotation pins.  I install red Loctite on the screws at one end, and on the other end I use blue Loctite, with some under the screw head so that it's held by adherence to the receiver when the screw is tightened.  In a mil-spec type trigger anything you do to eliminate movement will help to achieve a more consistent trigger break. 

On my latest build, the vendor I was buying the parts from didn't carry the anti-walk pins so I bought a set of KNS anti-rotate pins from them instead and I have to say that I like them a lot.  I've got my JP adjustable trigger set up for 3½ lbs break and total trigger travel of 1-2mm and it's my nicest trigger so far.  I can't feel absolutely any trigger movement until it breaks.

The hammer pin with a standard AR/M16 trigger group will always rotate with the hammer.  This is because the tension of the "J" spring locks the pin to the hammer.  Ordinarily, this is fairly benign, but in the case of blow-back, un-anodized 80% lowers, or enormously high round counts, it can lead to egging of the hammer pin holes.

KNS pins with the little anti-rotation bars, and similar designs keep the pin stationary eliminating this wear, albeit a very, very minor problem.