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Posted: 8/29/2026 11:29:58 AM EDT
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My PSA AR15 10.5 inch barrel 556 semiauto started shooting 2 to 4 shot bursts. It does it 3 to 4 bursts per 30 round magazine. What's the cause ? What do I need to replace to make it stop. I've shot about 2,000 to 3,000 rounds through it , then today it started shooting bursts. |
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check that your trigger is installed correctly
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Originally Posted By NTXGlocker: What trigger is in it? Is it stock or have you modified it? |
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Originally Posted By TW200: Regular OEM trigger that comes in PSA lower. I would take out the whole FCG, clean everything and relube, reinstall and check the springs and interfacing surfaces on the hammer, trigger, and disco. |
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Originally Posted By D_Man: Have you taken the trigger parts out recently? Sometimes an upside down disconnector spring can cause it to hang up and cause hammer follow and bursts. I would take out the whole FCG, clean everything and relube, reinstall and check the springs and interfacing surfaces on the hammer, trigger, and disco. |
Glock Derangement Syndrome > Trump Derangement Syndrome.
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Originally Posted By osprey21: Is this a build you put together? The first thing I would check would be for an upside down, a weak, or a broken disconnctor spring. I've shot thousands of rounds through it with no problem. then suddenly, out of the blue it started shooting bursts. |
Glock Derangement Syndrome > Trump Derangement Syndrome.
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Disco spring might be broken or have debris in there. Upside down is another culprit as mentioned. Another possibility is a chipped disconnector. |
"Who would deprive men of the use of fire for fear of their being burnt" - Cesare Beccaria's Essay on Crimes and Punishments
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Originally Posted By hoody2shoez: Make sure the trigger pins haven't walked. I had a rifle do that due to the pins walking. |
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Sic semper evello mortem tyrannis
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Good excuse to upgrade the trigger! Can you take photos of the trigger group in the lower? Maybe we can spot something. I would say it probably had the disconnector broke or chipped and it’s doing a hammer ride because the hammer can’t catch on the disconnector. |
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Originally Posted By dalle0001: Good excuse to upgrade the trigger! Can you take photos of the trigger group in the lower? Maybe we can spot something. I would say it probably had the disconnector broke or chipped and it's doing a hammer ride because the hammer can't catch on the disconnector. I'll take some images of the trigger group in the lower when I get back home |
Glock Derangement Syndrome > Trump Derangement Syndrome.
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I love my little pro gun Viking wife.
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Originally Posted By TW200: Here are the images of lower. https://www.ar15.com/media/mediaFiles/309020/20260829_161650-3819157.jpghttps://www.ar15.com/media/mediaFiles/309020/20260829_161113-3819159.jpg Do you know some basic function checks you can do with the upper off? Like testing the disco function by holding the trigger back, cocking the hammer with your thumb and letting it snap over the disco hook, then release the trigger and make sure the hammer jumps off the disco but is caught by the sear. If the hammer falls all the way down when you do this, it could be something with the disco or sear surfaces. |
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Well that does look pretty punked up. It's most likely an issue with the disconnector. Either it's worn, it's hanging up/not moving freely, or the disconnector spring is worn, broken, or installed wrong (by PSA, not you, obviously. A disconnector and spring are cheap. I'd just replace both, for good measure. |
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Yeah that looks okay to me. I’d replace it though just for the heck of it. I’m about 80% certain that it’s the disconnector though. Assuming you cleaned it and made sure nothing else is wrong it is definitely the trigger group being the culprit. I see you also posted about the fire pin. Here’s another possibility though and it happened to me once as well a debris got stuck in the fin pin channel of the bolt. What I would do is verify the fire pin and drop in and out of the bolt. It could be something is stuck in there. Also I vaguely remember Psa doing a recall about their triggers misfiring but I think that might have been Colt. |
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Originally Posted By dalle0001: Yeah that looks okay to me. I'd replace it though just for the heck of it. I'm about 80% certain that it's the disconnector though. Assuming you cleaned it and made sure nothing else is wrong it is definitely the trigger group being the culprit. I see you also posted about the fire pin. Here's another possibility though and it happened to me once as well a debris got stuck in the fin pin channel of the bolt. What I would do is verify the fire pin and drop in and out of the bolt. It could be something is stuck in there. Also I vaguely remember Psa doing a recall about their triggers misfiring but I think that might have been Colt. Could be slam firing. The burst cyclic rate was super fast. |
Glock Derangement Syndrome > Trump Derangement Syndrome.
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Originally Posted By TW200: Firing pin was tight inside bcg due to dirt and dry. Could be slam firing. The burst cyclic rate was super fast. Originally Posted By TW200: Originally Posted By dalle0001: Yeah that looks okay to me. I'd replace it though just for the heck of it. I'm about 80% certain that it's the disconnector though. Assuming you cleaned it and made sure nothing else is wrong it is definitely the trigger group being the culprit. I see you also posted about the fire pin. Here's another possibility though and it happened to me once as well a debris got stuck in the fin pin channel of the bolt. What I would do is verify the fire pin and drop in and out of the bolt. It could be something is stuck in there. Also I vaguely remember Psa doing a recall about their triggers misfiring but I think that might have been Colt. Could be slam firing. The burst cyclic rate was super fast. Ah that might be it. The fire pin should be able to drop in and out of the channel freely. It shouldn’t stick. |
I love how years ago everyone would be saying "hope you got a stamp for that lower" and "I'd delete this post if I were you" and now no one gives a crap 
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Isaiah 1:18 - "Come now, let us reason together," says the LORD: "though your sins are like scarlet, they shall be as white as snow"
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Do a disconnector test. Remove upper. Cock hammer. Pull trigger and hold…,catch with other hand With trigger pulled, push hammer back into disconnector. Release trigger. Did sear catch? Reconfirm multiple times looking for ways this could be defeated or uneven wear. Common issues are excessive dirt, excessive wear, uneven wear, sticking disconnector, damaged sear/hammer sear interface, damaged disconnector/hammer interface, sticking hammer or trigger. |
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Originally Posted By TW200: My PSA AR15 10.5 inch barrel 556 semiauto started shooting 2 to 4 shot bursts. It does it 3 to 4 bursts per 30 round magazine. What's the cause ? What do I need to replace to make it stop. I've shot about 2,000 to 3,000 rounds through it , then today it started shooting bursts. Odds are most likely that you are unintentionally bump firing. Make sure you have a firm grip and hold the trigger back for reset and it will stop. |
I'm no good at telling people what they want to hear when I dont believe it myself :)
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Originally Posted By Karankawa: Soft primers and a dirty firing pin channel might do that. Could have an out of battery detonation if so. Check the spent brass for swollen necks. No, that's not how an AR bolt/carrier works. |
I'm no good at telling people what they want to hear when I dont believe it myself :)
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Originally Posted By bigbore: Odds are most likely that you are unintentionally bump firing. Make sure you have a firm grip and hold the trigger back for reset and it will stop. I've had this happen before with my SSP triggers if I'm really concentrating on shooting tight groups. |
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Fortunately there are many videos out there covering removal and installation of AR lower parts and it never hurts to know how to take apart and assemble one al you wil need is a punch or something to push the pins out. If you function check don't let the hammer hit the rear of the mag well!, an easy way to trash a lower. |
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Originally Posted By TW200: Here are the images of lower. https://www.ar15.com/media/mediaFiles/309020/20260829_161650-3819157.jpghttps://www.ar15.com/media/mediaFiles/309020/20260829_161113-3819159.jpg Your hammer sear surface is fucked. See pic and circle 1. Also, your gun is cycling hard. The hammer hook is slamming back with enough force to impact the top of your disco and start damaging/deforming it. See circle labled 2.  As an armorer, we simply replace the entire fcg (trigger/hammer/disco and all associated springs) as a normal course of action to eliminate problem chasing with no drama. Cheap amd easy fix all things considered. |
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Originally Posted By LeviBarAlphaeus: Your hammer sear surface is fucked. See pic and circle 1. Also, your gun is cycling hard. The hammer hook is slamming back with enough force to impact the top of your disco and start damaging/deforming it. See circle labled 2. https://www.ar15.com/media/mediaFiles/601279/1000008297-3819871.jpg As an armorer, we simply replace the entire fcg (trigger/hammer/disco and all associated springs) as a normal course of action to eliminate problem chasing with no drama. Cheap amd easy fix all things considered. I noticed the wear points you circled earlier. This AR15 has been rode hard by me. I shoot real fast transitions on two 10 inch steel plates at 50 yards 30 round magazine after 30 round magazine. This AR15 gets real hot. Round count is probably closer to 5.000 to 6.000. |
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Originally Posted By TW200: Ah, I see... thanks. I noticed the wear points you circled earlier. This AR15 has been rode hard by me. I shoot real fast transitions on two 10 inch steel plates at 50 yards 30 round magazine after 30 round magazine. This AR15 gets real hot. Round count is probably closer to 5.000 to 6.000. I would also replace your action(buffer) spring at this time as well as your gas rings just for shits and giggles. Since you're performing invasive maintenance, might as well do a full refurb. If you want to go whole hog, change extractor and ejector along with new springs as well and give your bolt lugs onneither side of the extractor a good inspection for cracks at the rear of the roots. A 10x jewelers loupe will make this easier. If you are still getting that disco impact wear with a new action spring, you may also consider switching up to the next heavier buffer weight or throwing in a sprinco red/white spring to slow the bolt speed a tad. |
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| You're 'riding it hard' but not 'cleaning it hard'. You could probably solve your problem by blasting out the lower with carb cleaner, but the FCG must be replaced in order to be sure. Also, heating up the rifle like that, you're going to need a barrel soon. Basically you are using it up fast and you should already be thinking about buying a new one or building a new one on the old lower, assuming the pin holes are in-spec. But yeah, you should remove the FCG, clean the lower and install a new FCG as the minimum needed to restore correct function. |
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Originally Posted By LeviBarAlphaeus: I would also replace your action(buffer) spring at this time as well as your gas rings just for shits and giggles. Since you're performing invasive maintenance, might as well do a full refurb. If you want to go whole hog, change extractor and ejector along with new springs as well and give your bolt lugs onneither side of the extractor a good inspection for cracks at the rear of the roots. A 10x jewelers loupe will make this easier. If you are still getting that disco impact wear with a new action spring, you may also consider switching up to the next heavier buffer weight or throwing in a sprinco red/white spring to slow the bolt speed a tad. ^^Listen to this guy, he knows what he's talking about^^ A good cleaning, teardown, and inspection isn't really hard and there are tons of YouTube videos out there. It'll really help the gun and will also help you learn more about and respect your gun more. Make sure you pay attention to spring positioning. You can get punches from Harbor Freight if you don't have them. BTW, KAW Valley H3 buffer is only $50. You can often find them from vendors at $40. |
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