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Posted: 7/12/2026 2:51:25 PM EDT
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I have an AP5 that runs flawlessly with the factory MKE lower. I originally switched to a Lee Sporting lower with a Geissele SSA and an S7 Super Safety from GMR, but I had reliability issues and broke multiple trips. I then switched to an ASDesigns lower with the Geissele SSA. That solved the trip breakage issue, but now I started getting frequent failures to eject, which would then cause failures to feed. Since then, I've completely torn this gun down more times than I can count and replaced the following with genuine HK parts: Extractor Extractor spring Ejector Ejector spring Magazine catch I'm also running a 90° locking piece with a SilencerCo Omega 9K and only shoot 9mm NATO. After noticing a lot of resistance when cycling the bolt over the Geissele hammer by hand, I suspected the hammer geometry was causing the feeding issues. I replaced the Geissele trigger with a mil-spec AR trigger and installed a Warhammer Gen 2 MP5 hammer. I finally got a chance to test it this weekend. Semi-auto: 100% reliable. Super Safety: Light primer strike on round #2 almost every time. After searching around, I tried the following: Cut approximately 1/3 off the firing pin spring. Installed a Wolff extra-power hammer spring. Replaced the firing pin spring with a Bic pen spring. None of those changes made any difference. I'm still getting the same light primer strikes in Super Safety mode. At this point I'm pretty frustrated. I've probably put close to 2,000 rounds through this gun just trying to diagnose it. ASDesigns hasn't been very helpful beyond recommending a gunsmith in their area. Has anyone run into this combination of symptoms or have any ideas what I should be looking at next? Every time I fix one issue, another one pops up. Attached File Attached File |
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Originally Posted By cowboyrick: Check your bolt gap with your 90 degree locking piece. To large of bolt gap will prevent the firing pin form protruding enough. It may run fine in semi but will cause light strikes in frt. 0.015” in spec. This hammer will fall with the bolt 3/8” from being closed. It’s weird its even inconsistent when you run it manually, sometimes it will fall right when the rollers lock sometimes it’s way earlier than that. I’m just not sure what could cause that. Maybe I need to try a new trigger? The mil spec trigger with the SS cuts I’m running is from ASDesigns |
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Originally Posted By raverill: 0.015” in spec. This hammer will fall with the bolt 3/8” from being closed. It’s weird its even inconsistent when you run it manually, sometimes it will fall right when the rollers lock sometimes it’s way earlier than that. I’m just not sure what could cause that. Maybe I need to try a new trigger? The mil spec trigger with the SS cuts I’m running is from ASDesigns Originally Posted By raverill: Originally Posted By cowboyrick: Check your bolt gap with your 90 degree locking piece. To large of bolt gap will prevent the firing pin form protruding enough. It may run fine in semi but will cause light strikes in frt. 0.015” in spec. This hammer will fall with the bolt 3/8” from being closed. It’s weird its even inconsistent when you run it manually, sometimes it will fall right when the rollers lock sometimes it’s way earlier than that. I’m just not sure what could cause that. Maybe I need to try a new trigger? The mil spec trigger with the SS cuts I’m running is from ASDesigns I ran my mp5k with a printed lower and super safety for a while and it was never 100% . I had a lot of the stoppages you where having. My bolt gap was on the larger side so i put smaller rollers in and it greatly improved but not perfect. I finally bought the asdesigns lower with an arcfire v1 and it now runs perfectly. I think there is more slop in a super safety than in the arcfire. Also, I strictly run HK mags and use a steel rifle extractor spring instead of the copper collered 9mm spring. The copper springs are much weaker and wear out faster. |
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Originally Posted By cowboyrick: I ran my mp5k with a printed lower and super safety for a while and it was never 100% . I had a lot of the stoppages you where having. My bolt gap was on the larger side so i put smaller rollers in and it greatly improved but not perfect. I finally bought the asdesigns lower with an arcfire v1 and it now runs perfectly. I think there is more slop in a super safety than in the arcfire. Also, I strictly run HK mags and use a steel rifle extractor spring instead of the copper collered 9mm spring. The copper springs are much weaker and wear out faster. Good info, I only run HK mags as well. I do have an arcfire V2 I can pull out of an AR lower and try it on the ASDesigns lower and see if that solves the issue |
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I can only say my ASD stripped lower has been absolutely flawless. First with an Arcfire V1 and S3G, then a 45/90 Arcfire V2. The only malfunctions I had were with the AP5P stock lower with garbage MKE ejector, and a handful at that. Since I put the ASD lower and included ejector in, I'm over 3k without a single malfunction. Using an S3G as mentioned, titanium V5 slip trip, and either V1 or V2. Obviously, I prefer the 45-degree V2. I didn't trim the firing pin spring, or make any other change. Still the same stock MKE extractor and extractor spring. The bolt gap stayed nicely at the higher end throughout changing from a 115/120 stock, to 100, to 90, and finally 80 degree LP. I can run anything I want, suppressed or unsuppressed. |
Practice, the master of all things. - Augustus
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
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Originally Posted By krdt: I can only say my ASD stripped lower has been absolutely flawless. First with an Arcfire V1 and S3G, then a 45/90 Arcfire V2. The only malfunctions I had were with the AP5P stock lower with garbage MKE ejector, and a handful at that. Since I put the ASD lower and included ejector in, I'm over 3k without a single malfunction. Using an S3G as mentioned, titanium V5 slip trip, and either V1 or V2. Obviously, I prefer the 45-degree V2. I didn't trim the firing pin spring, or make any other change. Still the same stock MKE extractor and extractor spring. The bolt gap stayed nicely at the higher end throughout changing from a 115/120 stock, to 100, to 90, and finally 80 degree LP. I can run anything I want, suppressed or unsuppressed. Damn, makes me wonder if I got an out of spec lower. Just ordered a new SS cut trigger and SS from DZ, will report back |
Installed new trigger and super safety, still firing OOB 1/2” from roller locked  @krdt can you run this simple test and see if you can get your AP5 to release hammer OOB? Maybe they all are capable of it in SS mode and the only thing stopping light primer strikes is optimizing the bolt speed, hope I’m wrong  AP5/MP5 firing OOB with SS |
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Originally Posted By raverill: Installed new trigger and super safety, still firing OOB 1/2” from roller locked @krdt can you run this simple test and see if you can get your AP5 to release hammer OOB? Maybe they all are capable of it in SS mode and the only thing stopping light primer strikes is optimizing the bolt speed, hope I’m wrong  https://www.youtube.com/shorts/wWYH5xPLi8oYeah, as I said in PM, I have zero issues with OOB firing in FRT. My AP5P will only achieve hammer release when the bolt is fully into battery. However, I was curious after your PM and tried every possible variation to achieve an OOB release, and I finally got it to happen in semi. So, it will happen in semi, even decently out of battery, but in FRT it will only release in battery. What is your bolt gap? Does it happen in both semi and FRT or only FRT? Unfortunately, I don't have an FFL or I'd offer to take a look at it for you. While mine will release semi in an out-of-battery position, I don't have a bionic man finger, so I doubt I could achieve the speed needed to actually get it to fire out of battery. So, I'm not sure the OOB firing is the source of your issues, but that depends on what else is happening. |
Practice, the master of all things. - Augustus
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
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Originally Posted By raverill: Installed new trigger and super safety, still firing OOB 1/2" from roller locked @krdt can you run this simple test and see if you can get your AP5 to release hammer OOB? Maybe they all are capable of it in SS mode and the only thing stopping light primer strikes is optimizing the bolt speed, hope I'm wrong https://www.youtube.com/shorts/wWYH5xPLi8o |
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Originally Posted By D_Man: You need to cycle the bolt all the way back and then ease it forward slowly to the OOB position and try it. The lever on the SS needs to be in the rearward position which only happens after the bolt runs back over it. With you starting from the bolt closed position and just pulling it back a bit OOB, then the SS lever would be forward and yes, it's normal that you can pull the trigger in that condition but that's not what's happening when you shoot it. Hell, you can put the OEM MP5 trigger pack and lower on the gun and do the same thing you did in that video and it'll drop the hammer there too. Damn, I’m an idiot. Let me re-run the test and post new vid. I know this I’m definitely getting OOB hammer release when shooting as I’m getting stoppage from light primer strikes |
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Originally Posted By raverill: I’m definitely getting OOB hammer release when shooting as I’m getting stoppage from light primer strikes I did not read back to recall the details of your setup. Just chiming to alert you that bolt bounce induced stoppage often shows light primer strikes. |
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Originally Posted By dredeagle: I did not read back to recall the details of your setup. Just chiming to alert you that bolt bounce induced stoppage often shows light primer strikes. No, I appreciate your feedback, I was doing it wrong. Ok with a full charging handle rack, I can still release the hammer in this position, rollers not locked here Attached File |
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Originally Posted By raverill: No, I appreciate your feedback, I was doing it wrong. Ok with a full charging handle rack, I can still release the hammer in the position, rollers not locked here https://www.ar15.com/media/mediaFiles/421774/IMG_9356_jpeg-3802120.JPG  Best as I can tell comparing to your pic, mine can't fire unless it's a little bit more forward than yours. Looking into the magwell, I can get it to hammer fall just as the rollers start moving into the trunnion recesses, but it is very, very slightly before full lockup. I'd imagine when operating at speed it would lockup by the time the hammer rotated to fire. And I have to be death-dripping the trigger to get it to fire early like that. If you're getting it to fire sooner, then it might be something with the geometry on the rounded tail of your trigger or on the SS strut where it interacts with the trigger in SS mode. Basically, either there's too much material removed from one or both surfaces which allows you to pull the trigger earlier, or the geometry is ramped too much on one surface so that maybe the pulling on the trigger allows you to force the SS strut to forcefully rotate forward sooner than the slip-trip would push it forward. |
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Originally Posted By D_Man: I've been really trying to test this on mine, and it's a PITA trying to slowly creep the bolt forward those last increments to see where it can fall. Best as I can tell comparing to your pic, mine can't fire unless it's a little bit more forward than yours. Looking into the magwell, I can get it to hammer fall just as the rollers start moving into the trunnion recesses, but it is very, very slightly before full lockup. I'd imagine when operating at speed it would lockup by the time the hammer rotated to fire. And I have to be death-dripping the trigger to get it to fire early like that. If you're getting it to fire sooner, then it might be something with the geometry on the rounded tail of your trigger or on the SS strut where it interacts with the trigger in SS mode. Basically, either there's too much material removed from one or both surfaces which allows you to pull the trigger earlier, or the geometry is ramped too much on one surface so that maybe the pulling on the trigger allows you to force the SS strut to forcefully rotate forward sooner than the slip-trip would push it forward. @D_man great info, thank you. What exactly is the SS “strut”? I know this when I am pulling the trigger with enough force with the bolt in the position of the pic above, the trigger will rotate the super safety barrel enough to cause hammer release. Damn, I’ve been through 2 geissele SSA-Es, and 2 mil spec triggers trying to figure this out. Makes me wonder if it’s an out of spec lower issue. I could have purchased an HK SP5 by now
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Originally Posted By raverill: @D_man great info, thank you. What exactly is the SS "strut"? I know this when I am pulling the trigger with enough force with the bolt in the position of the pic above, the trigger will rotate the super safety barrel enough to cause hammer release. Damn, I've been through 2 geissele SSA-Es, and 2 mil spec triggers trying to figure this out. Makes me wonder if it's an out of spec lower issue. I could have purchased an HK SP5 by now The button, the "barrel", the roundy thing that rotates and slides side-to-side. The part in red is something that can happen I think if there is a more gradual ramp in the cut on the trigger tail, you basically are using the two ramped surfaces to move one and then the other; by pulling the trigger hard you force the SS to rotate enough that it can then fire, but only if the SS is already mostly rotated forward already. But remember that's you forcing that condition to occur with a dry gun. If you were actually firing it, you would have the bolt flying closed and rotating the SS into the fully forward position much faster than your input from the trigger could effect it I would think. |
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Originally Posted By raverill: @D_man great info, thank you. What exactly is the SS “strut”? I know this when I am pulling the trigger with enough force with the bolt in the position of the pic above, the trigger will rotate the super safety barrel enough to cause hammer release. Damn, I’ve been through 2 geissele SSA-Es, and 2 mil spec triggers trying to figure this out. Makes me wonder if it’s an out of spec lower issue. I could have purchased an HK SP5 by now Okay, after playing with mine more, I just don't think OOB is the source of your issue. It's possible, but I can get OOB release using the above method of only testing during the initial bolt closing after charging -- it will absolutely release before full bolt closing in FRT and in a similar place. Has zero effect on mine; it functions flawlessly. I think it happens far too fast to matter. By the time the hammer actually falls, the bolt is closed and locked. I initially thought it would only happen in semi, but it depends on where the FRT lever is positioned. If I hold it in just the right position/angle, it'll release OOB in FRT as well (when testing by charging, fully closing the bolt, pulling back, and then finding the release point). So, by both methods, it will OOB release given the right conditions. Regardless, that doesn't have any impact on my function. I would look at other considerations and not fixate on the fact that it will release OOB. Just for proof:  MP5K 80LP 60rd Dump 01 |
Practice, the master of all things. - Augustus
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers
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You need a rounded hammer. Took me 4 tries to get #4. You can assemble these wrong and break the trip. ( looks like you found that out ) I'm coming up up on 2 years trouble free. H&K SP5 Lee sporting lower Factory rounded AR15 hammer. Standard mil spec guts & springs. OG V1 greymarket SS and slip. SWR Octane 9 HD 150 grn round nose hard cast reloads 3.2 grns bullseye ( or unique ) Running against a reg trigger pack the ROF is right on with super safe. I'd go back to factory AR parts and MKE parts and start from scratch with a hammer that is rounded to let the slip & bolt over come it and fully reset it. Seems to me you are fighting the hammer and it is not fully setting causing hammer follow. |
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Originally Posted By OTHP: You need a rounded hammer. Took me 4 tries to get #4. You can assemble these wrong and break the trip. ( looks like you found that out ) I'm coming up up on 2 years trouble free. H&K SP5 Lee sporting lower Factory rounded AR15 hammer. Standard mil spec guts & springs. OG V1 greymarket SS and slip. SWR Octane 9 HD 150 grn round nose hard cast reloads 3.2 grns bullseye ( or unique ) Running against a reg trigger pack the ROF is right on with super safe. I'd go back to factory AR parts and MKE parts and start from scratch with a hammer that is rounded to let the slip & bolt over come it and fully reset it. Seems to me you are fighting the hammer and it is not fully setting causing hammer follow. I’ve always ran a rounded hammer, both on geissle and mil spec triggers |
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Originally Posted By raverill: I’ve always ran a rounded hammer, both on geissle and mil spec triggers I know you have a pile of money and time invested in this at thIs point. Hopefully like me you can just shoot when you want on your own property to get this sorted out. I don't see why you can't, many of us are running these SS setups in different configurations with different H&K and clone guns. Like I said I'm running the OG heavy slip only because it was all there was to buy and it works. Couple that with the fact that I've seen zero side effects or damage from my setup. So I'm not changing it. Do you run the silicone buffer tube over the recoil spring/rod? The one that came with my slip had two issues I had to correct. 1: it was to long. I had to trim it down. 2: It was just sliding around back and forth between the bolt and the rear cap. I used some masking tape to hold it in place to the rear so it didn't slide forward into everything. That was also causing me problems like yours. One Bang then light strike. Or bang bang stove pipe. Once I figured out the hammer. I still got the above light strikes or stove pipe on ejection. So I moved onto the buffer and started cutting it back. Then it worked so long as I didn't point the muzzle at the floor. Made it captive to the rear and it's been running ever since even with the same masking tape. I had planned on replacing with a more permanent fix but it runs and the tape is so far holding up fine even with oil & cleaning solvents. My son and I shoot the snot out of it. Matter of fact the transferables haven't been shot in a year or so due to the puregreed case and SCOTUS ruling on the clarifacation on one pull one shot bumbstocks are not MGs. Hope you get it figured out. I'm kinda out of ideas on yours after the buffer tube & hammer without it sitting right in front of me. I doubt it is your mags or gun if it works in factory config. Something added and changed is the culpret here not the gun it's self. |
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Originally Posted By OTHP: I know you have a pile of money and time invested in this at thIs point. Hopefully like me you can just shoot when you want on your own property to get this sorted out. I don't see why you can't, many of us are running these SS setups in different configurations with different H&K and clone guns. Like I said I'm running the OG heavy slip only because it was all there was to buy and it works. Couple that with the fact that I've seen zero side effects or damage from my setup. So I'm not changing it. Do you run the silicone buffer tube over the recoil spring/rod? The one that came with my slip had two issues I had to correct. 1: it was to long. I had to trim it down. 2: It was just sliding around back and forth between the bolt and the rear cap. I used some masking tape to hold it in place to the rear so it didn't slide forward into everything. That was also causing me problems like yours. One Bang then light strike. Or bang bang stove pipe. Once I figured out the hammer. I still got the above light strikes or stove pipe on ejection. So I moved onto the buffer and started cutting it back. Then it worked so long as I didn't point the muzzle at the floor. Made it captive to the rear and it's been running ever since even with the same masking tape. I had planned on replacing with a more permanent fix but it runs and the tape is so far holding up fine even with oil & cleaning solvents. My son and I shoot the snot out of it. Matter of fact the transferables haven't been shot in a year or so due to the puregreed case and SCOTUS ruling on the clarifacation on one pull one shot bumbstocks are not MGs. Hope you get it figured out. I'm kinda out of ideas on yours after the buffer tube & hammer without it sitting right in front of me. I doubt it is your mags or gun if it works in factory config. Something added and changed is the culpret here not the gun it's self. Thanks for the words of encouragement, I currently do not run a buffer. Plan is to try out the 100degree locking piece this weekend and report back. |
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Well ran 100degree and still got light primer strikes, with and without buffer put in the original locking piece (120 degrees) same result https://www.myinstants.com/en/instant/fahhhhhhhhhhhhhh-3525/?utm_source=copy&utm_medium=share |
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