AR15 Trigger guard

glassguy · August 21, 2020, 08:55 AM

I'm putting an AR15 kit together and all is good except for the roll pin that secures the trigger guard. The one in the kit measures .135, the holes in the receiver measure .123. I need to hit the local Ace hardware for the proper size. Can anyone please provide me with the proper diameter pin I should use? Another alternative would be to tap the 2 receiver holes and use a couple of hex set screws. Suggestions? Thanks G

Polinese · August 21, 2020, 10:05 AM

I've never measured mine but I'm pretty sure it's supposed to be a little bigger since it'll compress as you hammer it in and keep it from coming out.

HiBC · August 21, 2020, 10:12 AM

Roll pin sizes for an AR are metric.
Nominal for 3 mm is about .118 in. For a 3.5 mm its about .135.
I suggest you not tap anything.
Study which holes you are fixing to pin. The roll pin will go in the rear pair of holes.Don't drive a pin in the hole at the rear of the mag box. That hole does not go through. You do not want to drive a roll pin in a blind hole!!

There is a spring loaded plunger goes in the trigger guard for the forward hole.

The roll pin goes in the rear holes. Its a hinge pin. For winter,a cartridge tip will depress the plunger so the guard can swing down. Mittens,and all.

I'd say the pin size you want for the rear hole is 3 mm.(probably) Stainless preferred.

For myself,I'd just order a little AR-15 spring and pin and detent kit.

You'll need them sooner or later.

Double K · August 21, 2020, 10:17 AM

.002 bigger is typical, I've had good luck lubricating the pin and hole with grease then carefully starting the pin. Look at the hole on both sides to see if one has a tapered edge or less sharp. Also lay the gun on it's side and block the other, a small brass hammer is your best tool for the job.

I was thinking rear hole, when replacing the trigger guard with the aftermarket ones they give you two pins because they do away with the swing away feature with most of them.

glassguy · August 21, 2020, 04:29 PM

The pin that came with my kit I believe would break the aluminum at the holes if I tried to hammer it in. I guess I'll see if Ace has 3mm roll pins. Thanks for the replies

DnPRK · August 22, 2020, 02:51 AM

Don't hammer the pin. You risk breaking the little ears off the receiver.

Press the pin in place with a bench vise, small c-clamp or pair of channel lock pliers if you have a steady hand.

Google is your friend with information about installing the pin.

HiBC · August 22, 2020, 09:58 AM

Remember,that pin serves as a hinge pin. I forget which holes will be tighter,but if the hole in the guard provides interference,so the pin won't fall out,thenmthe holes in the lower receiver need clearance,so the guard can freely hinge down.
I may have it reversed,it might be the guard hole that is clearance and the receiver holes that are interference,

You said something about a .123 hole,thats a reasonable .005 clearance for the hinge to work on a 3mm,.118 + roll pin.

FWIW,if you take a 2 1/2 in or so long 1/4 -20 cap screw ,or bolt,grind the end square and flat,then straight into the end of the bolt drill a hole about .121,or 1/8 diameter,maybe 1/8 in deep. you will have a good 3 mm roll pin starter punch.
The punches are cheap to buy,or easy to make. There is no need for the frustration of trying to hold a short little pin with a hemostat as you smack it with a claw hammer.

The starter punch lets you easily start the pin square and straight.

Another option is drillng a clearance hole through a piece of flat stock...key stock would work.so long as the pin is longer than the stock thickness.
Start the pin into your workpiece using the hole you drilled to hold the pin square to the hole in the workpiece.

HiBC · August 22, 2020, 10:14 AM

Quote:

I was thinking rear hole, when replacing the trigger guard with the aftermarket ones they give you two pins because they do away with the swing away feature with most of them.

The problem with that idea is that the hole doesnot go through both tabs at the rear of the mag box. Its what we call a "blind hole" You can't remove the pin by driving it through. When you drive a roll pin into a blind hole,its not coming back out.

I confess,I made the mistake of driving the pin into the trigger guard at the forward holes,once. Been there,done that. Don't do anything radical if it happens to you. Just order another trigger guard and pin. You can save the lower by carefully using a dremel cut off wheel to cut only the trigger guard and pin.

kymasabe · August 22, 2020, 10:23 PM

I use magpul trigger guards and I screw them in place using a kit I get off ebay that works GREAT !!
https://www.ebay.com/itm/Standard-Tr...-/114349082683

Destructo6 · August 24, 2020, 10:14 AM

Quote:

Don't hammer the pin. You risk breaking the little ears off the receiver.

If you support the receiver's "ears" through which that pin passes, it will be fine. I've done it dozens of times and even just yesterday.

If you do not support the ear, there's a good chance it far one will snap off.

If you're going to spend for than a couple of dollars, a Magpul trigger guard, which does away with the roll pin/split pin, is only about $9.

**44 AMP** · August 24, 2020, 12:18 PM

TM 9-1005-249-34 says to install the roll pin with a 1/8" punch.

The roll pin fits tightly in the receiver but loosely through the hole in the trigger guard, so the guard will hinge down.

There is NO FRONT PIN in the GI guns or those made to GI dimensions. The trigger guard (assembly) has a spring loaded detent built in to serve as a latch

The trigger guard swings down to allow clearance of the winter trigger kit, which extends the trigger down the front of the pistol grip for use with mittens.

At least a few of the "arctic triggers" were made, I've seen pictures, but they were never issued or used, in any quantity, simply because some bright fellow(s) discovered that they weren't needed, with the guard swung down you can get your mittened paw on the trigger just fine.....AND....the Army issues trigger finger mittens, so you don't even need to swing the guard down.

Since yours is a "build" and you are using a trigger guard kit from yet some other maker, I have no idea what the specs they use are, or if it will fit.

Also, properly supporting the rear side of anything you are driving a pin into is just basic "shop sense".

Again, just to be clear, the rear hole (next to the pistol grip) goes all the way through and is for the roll pin (nom. 1/8" pin) The front hole, next to the mag well is a blind hole, does not go all the way through, because it is not a pin hole, it is a latch.

IF an aftermarket kit has you put a pin in the front hole, consider it permanent, because the only way you are ever going to remove it will be to drill it out.

August 21, 2020, 08:55 AM	#1
glassguy Member Join Date: August 11, 2009 Location: Living on the edge of Florida Posts: 81	AR15 Trigger guard I'm putting an AR15 kit together and all is good except for the roll pin that secures the trigger guard. The one in the kit measures .135, the holes in the receiver measure .123. I need to hit the local Ace hardware for the proper size. Can anyone please provide me with the proper diameter pin I should use? Another alternative would be to tap the 2 receiver holes and use a couple of hex set screws. Suggestions? Thanks G

August 21, 2020, 10:17 AM	#4
Double K Senior Member Join Date: June 16, 2020 Location: Colorado Posts: 486	.002 bigger is typical, I've had good luck lubricating the pin and hole with grease then carefully starting the pin. Look at the hole on both sides to see if one has a tapered edge or less sharp. Also lay the gun on it's side and block the other, a small brass hammer is your best tool for the job. I was thinking rear hole, when replacing the trigger guard with the aftermarket ones they give you two pins because they do away with the swing away feature with most of them. Last edited by Double K; August 21, 2020 at 10:22 AM.

August 22, 2020, 10:23 PM	#9
kymasabe Senior Member Join Date: June 10, 2005 Location: SW Florida Posts: 2,747	I use magpul trigger guards and I screw them in place using a kit I get off ebay that works GREAT !! https://www.ebay.com/itm/Standard-Tr...-/114349082683 __________________ God's creatures big and small, eat them one, eat them all.

August 24, 2020, 12:18 PM	#11
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,818	TM 9-1005-249-34 says to install the roll pin with a 1/8" punch. The roll pin fits tightly in the receiver but loosely through the hole in the trigger guard, so the guard will hinge down. There is NO FRONT PIN in the GI guns or those made to GI dimensions. The trigger guard (assembly) has a spring loaded detent built in to serve as a latch The trigger guard swings down to allow clearance of the winter trigger kit, which extends the trigger down the front of the pistol grip for use with mittens. At least a few of the "arctic triggers" were made, I've seen pictures, but they were never issued or used, in any quantity, simply because some bright fellow(s) discovered that they weren't needed, with the guard swung down you can get your mittened paw on the trigger just fine.....AND....the Army issues trigger finger mittens, so you don't even need to swing the guard down. Since yours is a "build" and you are using a trigger guard kit from yet some other maker, I have no idea what the specs they use are, or if it will fit. Also, properly supporting the rear side of anything you are driving a pin into is just basic "shop sense". Again, just to be clear, the rear hole (next to the pistol grip) goes all the way through and is for the roll pin (nom. 1/8" pin) The front hole, next to the mag well is a blind hole, does not go all the way through, because it is not a pin hole, it is a latch. IF an aftermarket kit has you put a pin in the front hole, consider it permanent, because the only way you are ever going to remove it will be to drill it out. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

August 21, 2020, 10:05 AM	#2
Polinese Senior Member Join Date: September 27, 2010 Posts: 947	I've never measured mine but I'm pretty sure it's supposed to be a little bigger since it'll compress as you hammer it in and keep it from coming out.

August 21, 2020, 10:12 AM	#3
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,283	Roll pin sizes for an AR are metric. Nominal for 3 mm is about .118 in. For a 3.5 mm its about .135. I suggest you not tap anything. Study which holes you are fixing to pin. The roll pin will go in the rear pair of holes.Don't drive a pin in the hole at the rear of the mag box. That hole does not go through. You do not want to drive a roll pin in a blind hole!! There is a spring loaded plunger goes in the trigger guard for the forward hole. The roll pin goes in the rear holes. Its a hinge pin. For winter,a cartridge tip will depress the plunger so the guard can swing down. Mittens,and all. I'd say the pin size you want for the rear hole is 3 mm.(probably) Stainless preferred. For myself,I'd just order a little AR-15 spring and pin and detent kit. You'll need them sooner or later.

August 21, 2020, 04:29 PM	#5
glassguy Member Join Date: August 11, 2009 Location: Living on the edge of Florida Posts: 81	The pin that came with my kit I believe would break the aluminum at the holes if I tried to hammer it in. I guess I'll see if Ace has 3mm roll pins. Thanks for the replies

August 22, 2020, 02:51 AM	#6
DnPRK Senior Member Join Date: August 24, 2001 Location: LC, Ca Posts: 1,917	Don't hammer the pin. You risk breaking the little ears off the receiver. Press the pin in place with a bench vise, small c-clamp or pair of channel lock pliers if you have a steady hand. Google is your friend with information about installing the pin.

August 22, 2020, 09:58 AM	#7
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,283	Remember,that pin serves as a hinge pin. I forget which holes will be tighter,but if the hole in the guard provides interference,so the pin won't fall out,thenmthe holes in the lower receiver need clearance,so the guard can freely hinge down. I may have it reversed,it might be the guard hole that is clearance and the receiver holes that are interference, You said something about a .123 hole,thats a reasonable .005 clearance for the hinge to work on a 3mm,.118 + roll pin. FWIW,if you take a 2 1/2 in or so long 1/4 -20 cap screw ,or bolt,grind the end square and flat,then straight into the end of the bolt drill a hole about .121,or 1/8 diameter,maybe 1/8 in deep. you will have a good 3 mm roll pin starter punch. The punches are cheap to buy,or easy to make. There is no need for the frustration of trying to hold a short little pin with a hemostat as you smack it with a claw hammer. The starter punch lets you easily start the pin square and straight. Another option is drillng a clearance hole through a piece of flat stock...key stock would work.so long as the pin is longer than the stock thickness. Start the pin into your workpiece using the hole you drilled to hold the pin square to the hole in the workpiece.