AR-15 Maintenance: Roll Pins

By Glen Zediker published on in Gun Gear, How To

AR-15s are pretty much pinned together. While a staple for many AR-15s, roll pins are not hard to work with, but a misstep could be catastrophic enough to permanently damage your AR-15. Here’s how to perform the essential construction operations associated with roll pins—the professional way.

collage showing start to finish of how to install a roll pin

Start the (oiled) roll pin using a starter punch. Drive it as far as you can with this tool. Switch to a nibbed-end punch and drive it on home. Protrusion should be equal on both sides, which means it ends up just a little below the surface. Finish with a dab of touch up paint. (Normally I’d have covered the area with masking tape to help ensure against accidental marring, but I left it off for better photo clarity.

AR-15 parts assemblies—ranging from the gas tube to magazine catch, bolt stop, bolt components, forward assist, sight parts, and more—are secured using roll pins. I’m not trying to talk anyone into banging on their guns, but there certainly may be times when a part replacement is in order, and something really simple, like replacing a bolt catch with something from the aftermarket, requires little more than a small collection of tools and a little insight into the process. Alternately, you might be ready to tackle a full-on build project, and that requiring a little larger tool collection.

two roll pin punches

Pin Punches. You really need a set of these. They are roll pin punches, one to start and one to finish. The starter punch has as its sole function and favor getting the oversized pin started into the hole. It’s sized to fit the outside of a pin; pin goes inside the punch. After the pin starts and is fully on its way, then switch punches to the one with the little nib on its end and send it on home. The nib fits into the hollow in a roll-pin and helps “grip” the pin so it can be seated to flush, plus, without unnecessary marring. Seating roll pins is a difficult and scratch-and-ding producing job without such a punch pair. Tip: drive the pin as far as you can using the starter punch, without contacting the part itself with the punch end.

A roll pin is a hollow pin with a split down its body. It’s oversized to the hole it fits into by about the gap width of the split. It squeezes down as it enters the hole and this tension keeps it in place. They are beveled on their ends but that’s not nearly enough to get one started gracefully, and that is the trick— gracefully or not—getting one started. Of course, there are specialty tools, and those are roll pin punches. Get some. For a basic build, you’ll need #s 1, 2, 3, and 4.

The ends of roll pins are often craggy or out-of-round, or both. These are not precision-made parts. Smooth and polish the ends of every roll pin you install. This doesn’t take much effort or time and is a worthwhile step. The easiest way is to lightly chuck one into a drill and spin it against some emery cloth or a stone. I do both ends because removal is easier when both ends are polished.

Steel pins going into aluminum holes make life way harder on the holes than the pins. I can also tell you that a drop of oil helps and will never diminish the hold of a roll pin. That also reduces any corrosive “sticktion” potentials between the aluminum and steel, making the pin come out easier too.

It doesn’t take undue effort to drive a roll pin, but true hits count. They can bend. Most roll pins are a little shorter than the full span of the hole. So, with the pin ends at equal depths, should leave each end a tad below flush with the part surface. A roll pin should never protrude above the surface to ensure no snagging potential.

Using a slave punch to line up the holes

Lining up. Get in the habit of using a capture or “slave” punch, which is simply another, correctly-sized punch, to line up associated holes prior to roll pin installation. Use the roll pin progress to drive the capture punch out. Really helps.

Ready for Work

You’ll notice that there are punches of varying lengths used in the work shown. The shorter ones are a little easier to operate but the longer ones are necessary for some installations, simply because they give clearance beyond rifle parts you don’t want to accidentally mis-hit with a hammer, or have the larger diameter handle portion in contact with a rifle receiver.

I often chuck up a small punch and polish the outside using emery cloth. They’re not all perfect, and at times, these little imperfections are annoying if not damaging. This is especially true when using one as a capture punch, such that it has to extend fully through the hole set. Likewise, with use, they often get a tad deformed around their edges, and that’s easy enough to true up with a stone.

Choose and use the right punch. A punch that’s too small for the pin will tend to deform and also expand the pin end. One that’s too large may also deform it, and won’t ultimately enter the pin’s hole to seat the pin-end correctly. Use a brass-headed tap-hammer for punching punches. It’s plenty enough power, and a slip won’t cause undue marring.

roll pin with the end deburred

Pre-Pinning. Get some emery or a hard Arkansas stone to run roll pin ends over before assembly. The ends are usually rough and irregular. It’s easy and makes for easier work. Assembly is greatly assisted but it’s also disassembly that improves when the ends are deburred. Just chuck the pin, lightly, in a drill and run on an angle for a few seconds.

I can’t tell you much about running a punch that you won’t learn on your own, but make sure the end is centered and stable and the punch is in-line with the pin. A “follow-through” sort of strike is usually better than mimicking a woodpecker. Whack! works better than tippy-tap-tippy-tap.

Oh, and tape! Use masking tape all over the working area. It is not a sign of weakness. Tape the fool out of everything around the installation and it’s less likely to need touch up afterward. However, touch-up finishes any pinning job and gives it a “factory fresh” appearance. I use a flat-black paint marker from Birchwood Casey. It works wonders.

Last Words

Aluminum alloy cracks, or dang sho can if it’s subjected to sharp impacts. Don’t allow gaps between the impact area and the workbench. Back up the receiver, especially on the trigger guard, and also rear sight windage knob (the screw is easily bent). A piece of wood is all that’s needed.

Can you reuse a roll pin? Sure. As long as it’s not been unduly damaged from removal. That means the ends are still tapered and the pin is still straight. This may not happen with some of the larger pins on the gun, but something like an ejector pin can be reused without worries.

Do you have a tip for maintaining your AR-15? Share it in the comment section.


The preceding is a specially-adapted excerpt from the book The Competitive AR-15: Builders Guide by Glen Zediker and Zediker Publishing. For more information visit ZedikerPublishing.com and to purchase go to BuyZedikerBooks.com

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Comments (11)

  • Spacegunner

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    The three smallest Grace punches are really soft (bendable), plus they are too long to get decent “guidance”. My three smaller punches look like arthritic fingers, or rigor-mortised snakes (after bending, and trying to straighten them multiple times). Brass & copper tend to be a bit more brittle than soft, mild steel. Good-alloy brass makes good punches, too.

    Reply

  • Spacegunner

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    I would NEVER modify a hole on a lower or upper receiver to accommodate a roll pin. Gas blocks are different because the hole may or may not be a standard size,and/or may have its diameter reduced for whatever reason.

    I do prefer pressing roll pins in, wherever it can be accomplished without the punch/hammer/bang technique. I use those for the final seating.

    Reply

  • Larry

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    Beware of “driving” a roll pin to retain the trigger guard. This is CRAZY. Use a “C” clamp to force it in and you will NEVER break the bottom tab :^)

    Reply

  • Louis

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    This is how I install (some) roll pins, mainly the trigger guard pin.

    After I get the pin started, I use a channel lock with the jaws heavily coated with electrical tape and push the pin in, kind of like a tightening a C-clamp. As I push it in, I adjust the jaws so I am not pushing on an angle.

    Reply

  • John

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    For the bolt catch try the KNS Precision Bolt Catch Pin. It’s a small pin that is secured with a very small e or c clip. You don’t have to drive it our out just slide it in and with a pair of tweezers push the clip on the end. You can throw away those special punches and roll pin starters and buy a pair of tweezers instead. Or you can purchase the billet lower receiver at New Frontier Armory that has a threaded pin for the bolt catch. I’d suggest a ball end allen to install or remove it.

    Reply

  • John

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    Roll pins are not all created equal. I see some modifying the hole to fit the roll pin, not always a good idea, it may be the roll pin that’s to big not the hole to small. As most ARs are made to mil spec most likely the holes are the right size. A quick search and you should find out what that size should be. The solution is to size the roll pin in a block of steel by drilling the correct size hole in a scrap of mild steel then lube the roll and chamfers the ends of the pin and drive it through. Drilling the hole out and the next roll pin may not fit so well. I have even, as the article suggest, put the pin in a drill and used a file to size the pin. Be careful as it doesn’t take much filing to get to the right size but if you have a good supply of pins you can simply try again. I have sized pins for the trigger guard on many occasion they always seem to be to large for what ever reason and have come in the standard pin type and of the rolled type without the slit opening where they compress, I usually don’t use those types on the trigger guards. A trigger guard pin pusher is strongly suggested. They aren’t very expensive and if you’re creative you can make one as I did.

    Reply

  • Spacegunner

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    Mr. Zediker is spot on (as usual) with this article about roll pins. I have built about a dozen AR’s (both upper & lower receivers) from scratch, and have learned similar things about roll pins.

    Two “words” of advice:
    1. STAY AWAY from GRACE USA roll-pin punches. All the punches in their 7-punch set are way too long for 99% of gunsmithing jobs, and the steel is softer than brass, or even copper! The 3 smallest-size punches are no straighter than my 57-year-old wobbly legs. They bend every which way with every use.
    2. It seems that most (if not all) roll-pin holes in gas blocks are too small for the roll pins that are supplied with the blocks. My routine practice is to now chase the holes with the next size larger (than the original hole), or next size smaller (than the pin) drill bit. I have had to improvise the roll pin on a couple of gas blocks because the holes were too small.

    Reply

    • Spencer

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      I worked in and or supervised machine shops from 1963 through 2007.
      Never once have I ever seen steel softer than brass. I’ve machined many alloys of both.

      Reply

  • GWDean

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    I purchased an extended length starter punch, specifically made for the bolt release roll pin. With the side of the receiver taped up, this makes it a snap to get that pin in.

    If your pin will not pick up the blind hole at the other side’s ear, get a supply of rolled “coiled” pins. They are chamfered on each end and will easily pick up the other hole.

    I bought a bag of 50 at Grainger Industrial Supply, for less than one item from an on-line vendor with S&H.

    Reply

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