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Posted: 2/22/2026 7:22:42 PM EDT
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Howdy, 2 range sessions ago I noticed a couple of unintentional doubles and didnt think much of it. Today I had a good number of them and a couple of FTFs with a dead trigger and dimpled primer. I tore the lower apart when I got home and didnt see anything glaringly wrong. The disconnector spring is visually fine and I dont see any damage to the disconnector. On the bench it function checks just fine. Am I on the right path thinking its the disconnector? I figured I'd ask before calling Geissele and seeing if they will sell me a disco+spring. Gun is a parts build that has been issue free until now (just under 7k total round count) - Geiselle SD3G trigger - toolcraft BCG (everything seems normal, gas rings are good, and the firing pin doesnt stick) - Ammo is reloads with CCI #400 primers. Seat depth looks good on all the ammo I pulled. I tore it apart and cleaned everything really well and will see if anything changes next Fri. I have a match next Sunday I'd like to shoot with this gun, so it be great to get it running right Friday. I can shoot my LVPO gun if needed though. Attached File |
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A little more information on the rifle may help, brand of receiver or something that was made out of an 80% where the machining might come into play. What buffer and buffer spring (action spring)? Did you build the upper or is it factory, and if it is something you built then I would check to make sure the gas block is indexed properly over the gas port in the barrel. You state that you tore the lower apart, hopefully this included removing the trigger system, and at that time you should look for anything like a blown primer, are the hammer and trigger springs on correctly. I would suggest giving it a thorough cleaning and lubrication just for process of elimination. Once cleaned and lubed, maybe try a one shot drill where you load a single round of ammo into a magazine. The insert the magazine into the magazine well, tug down to make sure it is fully seated, then manually cycle the action to load the one round of ammo. Now shoot the one round, and see if the gun will properly cycle, meaning it should fire, unlock from batter, extract the empty casing, eject the empty casing, fully recock the hammer, and lock back on the empty magazine. Repeat this several times. This one shot drill will help determine if the action is cycling back far enough. If it won't reliably lock back on the empty magazine, this may be an indication of a short stroking situation, which can be caused by several things (but not limted to) like friction, lack of gas pressure, misaligned gas tube to gas key and is causing binding issues, etc. If the gun will reliably lock back, then try it with 2 rounds, repeat several times. When doing this keep the trigger pressed to the rear after firing, to see if the hammer will reliably go back and get captured on the disconnector, and then when you release the trigger the hammer should reset back to what is called the hammer/trigger sear engagement. This will help show that the hammer is reliably going back far enough to get captured by the disconnector, and when you release the trigger that the hammer reliably go back forward and get captured by the trigger so that the trigger can be pressed rearward and get the gun to fire again. I would also suggest that you try a few different factory types of ammunition from a USA Manufacturer to see if it reacts different. CY6 Greg Sullivan "Sully" WeaponsArmorer SLR15 Rifles Defensive Edge Training (763) 712-0123 |
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Thanks for the responses! Lower: PSA lower Geissele SD3G Phase 5 bolt catch Odin extended mag release Radiant ambi safety ALG LPK Geissele Super 42 buffer+Spring with H2 buffer (it ejects around 4 oclock) Mil-spec dia buffer tube from my parts bin Upper: Geissele reciever, handguard, and charging handle Toolcraft bcg Larue 14.5" barrel + gas block + gas tube. Pinned miculek brake Thus far the rifle has been problem free through ~a dozen 2gun matches and practice. I guess I can pull the handguard off and check to make sure the gas block hasn't worked loose. Gas key on the BCG was fine. When I cleaned the lower I pulled the trigger group and safety out, then pulled the disconnector and spring to inspect. No debris found beyond carbon gunk. The disconnector works when I dry fire, hold the trigger, and pull the charging handle. I'll try factory ammo, but this rifle has already fired ~6500 of my reloaded ammo without issue. I guess Friday when I make it back to the range I'll bring a second rifle and mix/match halves to isolate the issue to the lower or upper. I'll do the one shot test as well to make sure it locks on an empty mag. I dont remember issues with bolt lock today, but its good to confirm. The two shot test is what I *think* it was failing today. I think the second shot was happening before I reset the trigger, but I'll try it again and hold the trigger to be sure. I didnt deliberately check that. It wasn't happening every time. I was shooting practice stages and had about a dozen doubles in 300 rounds fired. |
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Originally Posted By networkguru: Have you been shooting your reloads a lot in the firearm? Yes. ~6500 through this rifle and another ~4000 through my other gamer gun. I haven't had any ammo related issues thus far. No changes to setup on the Dillon, and the ammo from my range bag all passes gauge checks. Its all 75gr RMR 3gun bullets, Ramshot Tac, and CCI 400s. Velocity intentionally matches PSA's AAC 75gr so I can shoot factory ammo without much zero shift. |
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All I can say is I have heard many times that CCI 400's are soft and not recommended for AR15's. Plenty also say they use them with no problems. I couldn't tell you either way. But maybe something has changed on your disco or bolt that is causing this and the soft primers are exacerbating the issue? |
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Originally Posted By networkguru: All I can say is I have heard many times that CCI 400's are soft and not recommended for AR15's. Plenty also say they use them with no problems. I couldn't tell you either way. But maybe something has changed on your disco or bolt that is causing this and the soft primers are exacerbating the issue? Hopefully this weekend I can swap another known good upper onto this lower. That should help narrow down "its something in the trigger group" vs "its a gas issue or something with the firing pin" I could try a Ti firing pin as well. The FTFs that I had where the trigger was dead make me think the hammer rode forward with the bolt and just didnt have enough momentum to set off the primer those times. I think if primers were the primary cause, the issue would have shown up many thousands of rounds ago. |
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Its not the gun, its you and the S3G-trigger. I bet when you hold gun stock properly against chest and "yank" the trigger, it shoots fine = Shoot like it was 3G-match. The extremely light single stahe trigger causes unintended "bump-firing" when gun is not held firmly and trigger is pulled slowly. Think it like this: you finger is stationary, but gun moves back and forth due to recoil. S3G at least earlier came with 2 sets of springs to prevent this... Anyways, I had to swap to Geissele 2 stage duty trigger because of this. For IPSC/3G rifle S3G is/was fine. |
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Update: I reached out to Geiselle to purchase a disconnector and spring, and they offered to RMA the trigger. I'll swap the trigger out with a new SD3G in another gun to confirm its that, and then send it back. ETA: The difference between the springs is noticeable. I'll ask the G bois if I should start with that before replacing. It looks like they sell spring kits, but disconnectors require trigger replacement. Attached File |
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I shot a 2gun match today with the same rifle and a different SD3G trigger. Zero issues all day. I'll swap the disconnector spring in the original trigger and see if that works next weekend. I bet it does. |
When we face the impossible, we dream a way through. Awakened with purpose, inspiring generations anew...
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Last update in case anyone reads this while searching to troubleshoot doubles. I bought a spring kit from Geissele and that solved my issue. Old disco spring on the left, new on the right: Attached File The trigger spring kits are $12 for all three springs. I'll probably start swapping them out every 5k on my match triggers as cheap insurance. |
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