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 AR-15, 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.
A roll pin is a hollow pin with a split. 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 often not nearly enough to get one started gracefully, and that is the trick--gracefully or no, of getting one started. Of course there is a specialty tool: a roll-pin punch. Get some. For a basic build, you'll need Nos. 1, 2, 3 and 4.
Polish
The ends of roll pins are often craggy, 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 thing is to lightly chuck one into a drill and spin it against some emery or a stone. I do both ends but only the entry is necessarily smoothed. Removal is easier when both ends are polished. Steel pins going into aluminum holes make life way harder on the holes than on the pins. I can also tell you that a drop of oil helps and will never diminish the effectiveness of a roll pin. That also reduces any corrosive "sticktion" potentials, meaning they come back out easier.
It doesn't take much effort to drive a roll pin (with a couple of exceptions), but true hits count. They can bend. Most roll pins are a little shorter than the full span of the hole, so a sano job finishes with the pin ends at equal depths, and that should have each end a tad below flush with the part surface. A roll pin should never protrude above the surface to ensure no snagging potential.
Punch Size
You'll notice there are punches of varying lengths used in the work shown and the shorter ones are a little easier to operate. The longer ones are necessary for some installations simply because they protrude freely and clearly beyond rifle parts you don't want to accidentally miss-hit with a hammer or have the larger diameter handle portion in contact with a rifle receiver.
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I often chuck up a small punch and polish its outside. They're not all perfect, and sometimes 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. Same sort of procedure for polishing most anything: spin against emery cloth until the metal is smooth. Likewise, with use they often get a little deformed around their edges, and that's easy enough to true backup with a stone.
If a punch is too small for the pin, it will tend to deform and also expand the pin end. One that's too large may do the same and also won't ultimately enter the pin's hole to seat the pin's end correctly.
Use a brass-headed tap-hammer for punching punches. It has plenty enough power and a slip won't cause undue marring.
I can't tell you much about running a punch you won't learn on your own, but make sure the end is centered and the punch is in-line with the pin. A "follow-through" sort of strike is usually better than mimicking a woodpecker.
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As mentioned, oil pins before installation. It sure makes them seat easier and will in no way affect their holding power.
Oh, and tape. Use masking tape all over the immediate work 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 sure can, if it's subjected to sharp impacts. Back up the receiver especially on the triggerguard, 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 probably won't happen with some of the larger pins on the rifle, but something like an ejector pin can be reused without worries.
Consider your sources. I just have to comment on this because it's stupid. I've seen many places on the Internet where folks are showing all about how to install pieces-parts on AR-15s and they suggest a pair of pliers with its jaws coated over with tape to install roll pins. The idea is to press the pin in place. That will bend the pin and no matter how much tape is used mar the opposite point on the rifle part. Just don't do that. Pin punches aren't expensive. Rifle parts can be.
Shameless Plug. 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 www.zediker.com or call (662) 473-6107.
BROWNELLS
200 S. FRONT ST.
MONTEZUMA, IA 50171
(641) 623-4000
WWW.GUNSMAGAZINE.COM/BROWNELLS
BIRCHWOOD CASEY
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EDEN PRAIRIE, MN 55344
(952) 937-7933
WWW.GUNSMAGAZINE.COM/BIRCHWOOD-CASEY-LABORATORIES
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