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Posted: 8/2/2026 9:26:11 PM EDT
| I have a 9mm upper I just can't get working with a trigger kicker. I think the problem is the bcg, so I'm going to buy another and keep trying. What are you guys using in your 9mm builds with FRTs or trigger kickers? |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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I have a KAK enhanced 9mm bcg arriving tomorrow for a Colt 6951. KAK advertises on their website that it will work with a trigger kicker. I emailed them before I ordered it and they assured me it will work. Guess we will see. The factory Colt bcg is ramped but has the weight in the rear that made contact with the kicker before the carrier is supposed to. Being that it is a Colt lower it has the sear web in the lower and only the trigger kicker will work without milling the lower out. They used to sell an “extra heavy Bcg weight” that was cut to allow FRTs and you could swap it into a 9mm Bcg. They said they pulled it off their website due to the tungsten shortage and not knowing when they will be able to make more. I don’t want to cut up my Colt bcg, I haven’t been able to find the weights for sale anywhere. |
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I have had success with multiple Foxtrot Mike 9mm bolts with Disruptors and Trigger Kickers. The bolt weight does not have to be cut, so it is an easy solution. I could not get my Kaw Valley Precision bolt to work in any of my 9mm setups. (In FRT mode, that is...) Edited to add: Tell us what buffer and spring you are using. The buffer system is the source of many FRT issues in 9mm blowbacks... |
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Originally Posted By Ken6PPC: I have had success with multiple Foxtrot Mike 9mm bolts with Disruptors and Trigger Kickers. The bolt weight does not have to be cut, so it is an easy solution. I could not get my Kaw Valley Precision bolt to work in any of my 9mm setups. (In FRT mode, that is...) Edited to add: Tell us what buffer and spring you are using. The buffer system is the source of many FRT issues in 9mm blowbacks... The buffer system is definitely a problem, but I've got a Tromix 9mm buffer on the way. Problem I'm trying to correct with a new bolt is a timing issue. When you hand cycle the bolt, the hammer is not held until the last second, rather the hammer is getting released way too early and following the bolt home. Its hard to tell, but I think its dropping somewhere around when the bolt face clears 1/3 of the way through the ejection port. |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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Originally Posted By shaggy: The buffer system is definitely a problem, but I've got a Tromix 9mm buffer on the way. Problem I'm trying to correct with a new bolt is a timing issue. When you hand cycle the bolt, the hammer is not held until the last second, rather the hammer is getting released way too early and following the bolt home. Its hard to tell, but I think its dropping somewhere around when the bolt face clears 1/3 of the way through the ejection port. That is WAY too early. Are you certain your bolt is pushing the hammer down enough to actually lock? I have a FM upper and lower with a FM bolt that works very well with a Trigger Kicker. Cycling the bolt slowly by hand, it is very obvious when my hammer is released. Are you using a Colt trigger? https://www.youtube.com/watch?v=OlG6maUG1Ks |
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Originally Posted By Ken6PPC: That is WAY too early. Are you certain your bolt is pushing the hammer down enough to actually lock? I have a FM upper and lower with a FM bolt that works very well with a Trigger Kicker. Cycling the bolt slowly by hand, it is very obvious when my hammer is released. Are you using a Colt trigger? https://www.youtube.com/watch?v=OlG6maUG1Ks I tested it with a different 9mm bolt and the timing was pretty much spot on. But its an older style bolt (I don't know the manufacturer) that looks like its had some aftermarket machining. Bolt bounce was still there, but I think at least it narrowed down the timing issue to the bolt. I'm hoping to figure out which newer bolt type works and get one to complete my current build and get a spare or two. |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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Originally Posted By Ken6PPC: I have had success with multiple Foxtrot Mike 9mm bolts with Disruptors and Trigger Kickers. The bolt weight does not have to be cut, so it is an easy solution. I could not get my Kaw Valley Precision bolt to work in any of my 9mm setups. (In FRT mode, that is...) Edited to add: Tell us what buffer and spring you are using. The buffer system is the source of many FRT issues in 9mm blowbacks... @Ken6PPC Can you provide a picture of the bottom of the Foxtrot Mike 9mm bcg? Trying to see if the weight has the clearance I need. I'm trying to get a Colt 6951 going with a trigger kicker and the factory colt bcg weight hits the kicker prior to the rear section of the carrier. My KAK enhanced 9mm BCG arrived and is nearly identical to the Colt bcg, weight and all. It doesn't work with the trigger kicker either, even though their tech support and website clearly states that it is compatible with the trigger kicker. Not sure if I can even return it at this point as the trigger kicker put a nick in the bcg weight. I may just 3d print the jig and clearance the weight myself. I have the tromix 9mm buffer so removing a little weight would probably be okay. |
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@1BMF I don't currently have a picture hosting site, so I can't upload any pictures here, and I couldn't find a good picture that shows that area of a FM bolt weight well enough to link to. Here is a link to a FM 9mm bolt on their website: https://store.fm-products.com/products/fm-products-5397-866a385f-576d-4c31-9957-4c319b7f5250,https://store.fm-products.com/products/fm-products-5397-866a385f-576d-4c31-9957-4c319b7f5250 Send me a PM with your email address and I will email some pictures that I just took of my newest and one of my older FM 9mm Bolts. In any case, the weight in FM 9mm bolts is perfectly FLUSH with the rear trip surface of the bolt. The only ones currently available from FM has an extra cut in the feed ramp (the cut underneath the extractor) that worried me before I ordered one. I was concerned it might cause problems with my FRT's, but mine runs well with two Disruptors and one TK. The bolt weight is flush with the rear trip surface, just under the word PATENT in this picture. It does not have to be cut like many 9mm bolts do.  |
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Originally Posted By Ken6PPC: @1BMF I don't currently have a picture hosting site, so I can't upload any pictures here, and I couldn't find a good picture that shows that area of a FM bolt weight well enough to link to. Here is a link to a FM 9mm bolt on their website: https://store.fm-products.com/products/fm-products-5397-866a385f-576d-4c31-9957-4c319b7f5250,https://store.fm-products.com/products/fm-products-5397-866a385f-576d-4c31-9957-4c319b7f5250 Send me a PM with your email address and I will email some pictures that I just took of my newest and one of my older FM 9mm Bolts. In any case, the weight in FM 9mm bolts is perfectly FLUSH with the rear trip surface of the bolt. The only ones currently available from FM has an extra cut in the feed ramp (the cut underneath the extractor) that worried me before I ordered one. I was concerned it might cause problems with my FRT's, but mine runs well with two Disruptors and one TK. The bolt weight is flush with the rear trip surface, just under the word PATENT in this picture. It does not have to be cut like many 9mm bolts do. https://cdn.filestackcontent.com/c4LbFcgfReWmPUA14Gc9#file.jpg Is that Colt mag compatible? According to the FM page it says glock, but my understanding was that most glock compatible bolts we I'll work in both. |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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Originally Posted By shaggy: Is that Colt mag compatible? According to the FM page it says glock, but my understanding was that most glock compatible bolts we I'll work in both. Hmm, I do not know if the FM 9mm bolts are Colt mag compatible. I don't even own a Colt 9mm magazine. Doing a Google search, I found references to Glock style bolts ARE NOT Colt magazine compatible, AND references that said they ARE Colt magazine compatible. |
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Originally Posted By Ken6PPC: Hmm, I do not know if the FM 9mm bolts are Colt mag compatible. I don't even own a Colt 9mm magazine. Doing a Google search, I found references to Glock style bolts ARE NOT Colt magazine compatible, AND references that said they ARE Colt magazine compatible. I just emailed FM, and unfortunately none of their 9mm bolts are Colt-mag compatible. |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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Originally Posted By shaggy: I just emailed FM, and unfortunately none of their 9mm bolts are Colt-mag compatible. Hmmm. And here I am newly decided to introduce my Mean Arms mags to the circular file. All set to go colt mag exclusive then you deliver bad news from FM. I found this: FM Upper - Colt Mags So, I haven't abandoned my plans ... yet. Guess I'll test fit to my DOE lower to see what's what. |
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Originally Posted By dredeagle: Hmmm. And here I am newly decided to introduce my Mean Arms mags to the circular file. All set to go colt mag exclusive then you deliver bad news from FM. I found this: FM Upper - Colt Mags So, I haven't abandoned my plans ... yet. Guess I'll test fit to my DOE lower to see what's what.  |
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Originally Posted By 1BMF: @Ken6PPC Can you provide a picture of the bottom of the Foxtrot Mike 9mm bcg? Trying to see if the weight has the clearance I need. I'm trying to get a Colt 6951 going with a trigger kicker and the factory colt bcg weight hits the kicker prior to the rear section of the carrier. My KAK enhanced 9mm BCG arrived and is nearly identical to the Colt bcg, weight and all. It doesn't work with the trigger kicker either, even though their tech support and website clearly states that it is compatible with the trigger kicker. Not sure if I can even return it at this point as the trigger kicker put a nick in the bcg weight. I may just 3d print the jig and clearance the weight myself. I have the tromix 9mm buffer so removing a little weight would probably be okay. I myself have been thinking of getting a FM bolt to replace my KAK Enhanced 9mm bolt. My 11” AR9 still doesn’t function in FRT mode (runs fine in semi) with either a DTT trigger or an Atrius Selector that I’ve tried in it. I’ve also tried different weight buffers ranging from a standard carbine all the way to their 10oz enhanced buffer, and even swapped in their tungsten weight in the bolt. ETA: nevermind, just read they’re not Colt mag compatible  |
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Originally Posted By Willisinnawoods: I myself have been thinking of getting a FM bolt to replace my KAK Enhanced 9mm bolt. My 11” AR9 still doesn’t function in FRT mode (runs fine in semi) with either a DTT trigger or an Atrius Selector that I’ve tried in it. I’ve also tried different weight buffers ranging from a standard carbine all the way to their 10oz enhanced buffer, and even swapped in their tungsten weight in the bolt. ETA: nevermind, just read they’re not Colt mag compatible Originally Posted By Willisinnawoods: Originally Posted By 1BMF: @Ken6PPC Can you provide a picture of the bottom of the Foxtrot Mike 9mm bcg? Trying to see if the weight has the clearance I need. I'm trying to get a Colt 6951 going with a trigger kicker and the factory colt bcg weight hits the kicker prior to the rear section of the carrier. My KAK enhanced 9mm BCG arrived and is nearly identical to the Colt bcg, weight and all. It doesn't work with the trigger kicker either, even though their tech support and website clearly states that it is compatible with the trigger kicker. Not sure if I can even return it at this point as the trigger kicker put a nick in the bcg weight. I may just 3d print the jig and clearance the weight myself. I have the tromix 9mm buffer so removing a little weight would probably be okay. I myself have been thinking of getting a FM bolt to replace my KAK Enhanced 9mm bolt. My 11” AR9 still doesn’t function in FRT mode (runs fine in semi) with either a DTT trigger or an Atrius Selector that I’ve tried in it. I’ve also tried different weight buffers ranging from a standard carbine all the way to their 10oz enhanced buffer, and even swapped in their tungsten weight in the bolt. ETA: nevermind, just read they’re not Colt mag compatible I’m going to removed the bcg weight and see if it will function check with the trigger kicker. I picked up a tromix 9mm buffer, I’ve have good luck with their H3’s in 556 guns with disruptors and 3d printed FRTs. Update: I got the bolt weight removed and the trigger kicker still doesn’t function check properly. As I cycle the bolt it pushes the trigger forward but will not lock it forward. So as the bolt goes forward it allows the trigger to be pulled progressively, would just get hammer follow. I’m kind of at a loss, this exact fcg and kicker works with a 556 bcg in a colt lower with the sear web. |
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Let me add a bit to the discussion. I am working to adapt a SS or TK to an Extar EP9. The tail of your bolt needs to mimic the dimensions of a regular AR15 bolt. On the Extar I need to grind/drill/dremel a void or chamber about 40-42mm from the tail, along with a channel of similar depth leading to the trigger channel. Both the SS and TK extend up into the bolt and need space to work. The SS swings through an arc, the TK has a tendency to lift up and can bind w/o proper relief. On an AR as the bolt closes it isn't pushing on the tip of the finger, the finger is up inside and the bolt is 'hooked' onto the SS finger and pushing below the tip of the finger. The distance from the tip of the bolt tail to your cut will determine the hammer release point. I had the Extar dropping about 1/16-1/8 from fully closed, then ground just a tiny, tiny bit more and apparently that was too much, it refused to drop after that. I also think the 3d printed SS was allowing too much flex to get a consistent release point. When it did run it chugged along at about 475-500 rpm. If you google Extar and FRT, there are some recent, and a few older posts, with links to pictures showing the necessary bolt mods. One user states 1.625-1.635 inches from the tail of the bolt is where the cut needs to be. I would start out with a greater distance from the tail as you can always take more off but it's hard to add metal back. https://www.reddit.com/r/extar/comments/1u0lqj3/dropping_by_let_you_know_that_you_can_do_it_to/?share_id=lC-X5XUPkNnq_euIiCsKI&utm_content=1&utm_medium=ios_app&utm_name=ioscss&utm_source=share&utm_term=1 |
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I had more time to mess with mine yesterday. My current setup just wasn’t working and it seemed that my 9mm bolt (both Colt and KAK) weren’t traveling rearward enough. I swapped my entire 9mm upper onto an LWRC lower with a disruptor and carbine stock, with a tromix h3 inside. Would reset for semi auto but not frt, which is odd because the h3 tromix buffer is shorter than the 4” 9mm tromix. Then I tried the 9mm upper onto another lower with a disruptor and a2 stock with rifle buffer, this one actually did reset and cycle in semi and frt mode if I cycled it fast enough. This got me to think that a standard carbine buffer tube with 4” buffer is short stroking and not traveling rearward enough to reset the hammer fully. Google AI convinced me an A5 buffer tube and rifle length spring coupled with my tromix 4” 9mm buffer would work lol. So I’ll have the buffer tube here soon. Oddly enough the Colt bcg would hand cycle with the disruptor but the KAK would not. Since the disruptor won’t fit in the Colt lower, I ordered a Colt style mag well adapter and will try to run with the upper on a spare lower with the A5 buffer tube before I break the factory staked castle nut. If that all works I may build another rifle out of the kak bolt or something lol. |
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I had more time to mess with mine yesterday. My current setup just wasn’t working and it seemed that my 9mm bolt (both Colt and KAK) weren’t traveling rearward enough. I swapped my entire 9mm upper onto an LWRC lower with a disruptor and carbine stock, with a tromix h3 inside. Would reset for semi auto but not frt, which is odd because the h3 tromix buffer is shorter than the 4” 9mm tromix. Then I tried the 9mm upper onto another lower with a disruptor and a2 stock with rifle buffer, this one actually did reset and cycle in semi and frt mode if I cycled it fast enough. This got me to think that a standard carbine buffer tube with 4” buffer is short stroking and not traveling rearward enough to reset the hammer fully. Google AI convinced me an A5 buffer tube and rifle length spring coupled with my tromix 4” 9mm buffer would work lol. So I’ll have the buffer tube here soon. Oddly enough the Colt bcg would hand cycle with the disruptor but the KAK would not. Since the disruptor won’t fit in the Colt lower, I ordered a Colt style mag well adapter and will try to run with the upper on a spare lower with the A5 buffer tube before I break the factory staked castle nut. If that all works I may build another rifle out of the kak bolt or something lol. |
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Originally Posted By 1BMF: I had more time to mess with mine yesterday. My current setup just wasn’t working and it seemed that my 9mm bolt (both Colt and KAK) weren’t traveling rearward enough. I swapped my entire 9mm upper onto an LWRC lower with a disruptor and carbine stock, with a tromix h3 inside. Would reset for semi auto but not frt, which is odd because the h3 tromix buffer is shorter than the 4” 9mm tromix. Then I tried the 9mm upper onto another lower with a disruptor and a2 stock with rifle buffer, this one actually did reset and cycle in semi and frt mode if I cycled it fast enough. This got me to think that a standard carbine buffer tube with 4” buffer is short stroking and not traveling rearward enough to reset the hammer fully. Google AI convinced me an A5 buffer tube and rifle length spring coupled with my tromix 4” 9mm buffer would work lol. So I’ll have the buffer tube here soon. Oddly enough the Colt bcg would hand cycle with the disruptor but the KAK would not. Since the disruptor won’t fit in the Colt lower, I ordered a Colt style mag well adapter and will try to run with the upper on a spare lower with the A5 buffer tube before I break the factory staked castle nut. If that all works I may build another rifle out of the kak bolt or something lol. Sorry to hear the KA bolt doesn't work. I already ordered one of them, so it sounds like thats $120 down the drain for me. I have a Colt style bolt and have been having timing/reset issues with the kicker. When I drop that same upper and bolt on a lower with an AS Designs FRT, it hand cycles perfectly. I think the issue may be that the kicker is slightly bent to the right to avoid the channel in the underside of the bolt for the buffer retaining pin. On all my my Colt style 9mm bolts the underside of the bolt has less material cut away than a 556 bolt. I think some of this material on the right side of the bolt is just enough to trip the kicker way too early, because of the right side bend of the kicker. Of course it could be something completely different, but thats all I can come up with. 
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"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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Originally Posted By shaggy: Sorry to hear the KA bolt doesn't work. I already ordered one of them, so it sounds like thats $120 down the drain for me. I have a Colt style bolt and have been having timing/reset issues with the kicker. When I drop that same upper and bolt on a lower with an AS Designs FRT, it hand cycles perfectly. I think the issue may be that the kicker is slightly bent to the right to avoid the channel in the underside of the bolt for the buffer retaining pin. On all my my Colt style 9mm bolts the underside of the bolt has less material cut away than a 556 bolt. I think some of this material on the right side of the bolt is just enough to trip the kicker way too early, because of the right side bend of the kicker. Of course it could be something completely different, but thats all I can come up with. https://i.postimg.cc/x8zJXCjC/1000003470.jpg Yeah that’s possible. I’ll take some side by side photos. Optics planet got me a kak a5 tube in like 2 days but I’m out of town. I’ll try it out tomorrow to see what happens. I also ordered an R&D mag well adapter to use Colt style mags in a spare lower but that hasn’t shipped yet. But for now at least I’ll be able to assemble the rest and see if it will hand cycle and function test tomorrow. I have a spare disruptor to try and I might swap over a trigger kicker to see if the buffer tube was the problem. I’ll post an update tomorrow |
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My KAK bolt arrived today. The bottom right side of the KAK hybrid bolt is cut similar to my Colt style bolts. The way I'm seeing it is that there's only a very slim area where the kicker must be positioned for it to function correctly; it can't be in the recoil pin channel and it can't be near the edge of the bolt. The yellow line is I think the channel the kicker has to remain in during forward bolt travel. My kicker has enough side to side play that it could easily be out of that yellow area. By cutting away more of the underside of the bolt on the right side it would give a little more leeway for the kicker to be slightly out of place. And remember, that extra material isn't there in a 556 bolt carrier, so in 556 you already have more leeway for the kicker built-in. Someone please shoot holes in my theory before I break out the dremmel and really fuck up my bolt.  *Disregard the bolt weight. I've properly cut that back in my other bolt, but still have the same issue. 
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"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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I saw a picture of a PSA 9mm bcg and it the center of the bottom was cut much wider. I installed the a5 buffer tube but that did not fix my issues. Some reason I am still getting a dead trigger in frt and the hammer is not being fully reset. Try and tinker with in this weekend but I may be busy building unregistered sbr’s lol |
  Here is the weight removed from the KAK enhanced 9mm bcg. It appears to be identical to the Colt weight. The Colt weight is held in by a coiled roll pin whereas the KAK has a regular roll pin. As you can see the weight extends forward on the bcg along the sides. It is also ramped for the hammer to cycle. I’ve been using the Tromix 9mm 4” buffer. I originally tried to get my Colt 6951 functioning with a trigger kicker as the Colt receiver has the sear web. I believe the weight was interfering with that and it didn’t function check. Then I tried it in various lowers that each have a partisan disruptor. For some reason it seemed to function check on a spikes lower with an a2 stock, but not in a lower with a carbine buffer. So I bought an A5 buffer tube that is longer and it still wouldn’t function check with the disruptor. So then I removed the weight from the KAK bcg and tried it in a lower with super safety and tromix h3 buffer. It actually function checked 100%. Shit now we’re getting somewhere. I swapped out the Tromix h3 for the 4” 9mm Tromix and it failed to reset in frt as before. So then I installed a super safety into the lower that had the A5 buffer tube, then installed the Tromix 4” 9mm buffer with a rifle length spring. Voila, now it function checks with the super safety and proper buffer. Now I need to cut the KAK bcg weight to accommodate the super safety lever and it should work. I’m also waiting for optics planet to ship the 9mm mag well adapter, which might be a few more weeks. What buffers is everyone else running in their 9mm AR15’s with FRTs? I have had good luck with the Tromix h3 but I’m starting to the 4” may have been why I had so many problems. |
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Originally Posted By Ken6PPC: I could not get my Kaw Valley Precision bolt to work in any of my 9mm setups. (In FRT mode, that is...) Same here im looking for another option for colt mag setup. |
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I cannot get a kicker working with a 9mm set up reliably. There's something definitely off with the timing when I hand cycle it, and I've tried about five different 9mm bolts. If anyone has one that works with a kicker I'd be really interested in your particular setup. The only thing I can think of at this point is it may have something to do with the bolt ramping. Works fine with an ARC fire though. Ordered a Partisan over the weekend, so I'll see if that works. |
"Government is not the solution to our problem; government is the problem." - Ronald Reagan
"Everything I want to do is illegal." - Joel Salatin
"Everything I want to do is illegal." - Joel Salatin
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HelpfulGuerilla posted this chart (put together by Blowback9) in another thread. It has some important details when someone is trying to get their 9mm AR to run. Look at the columns that lists Ramping Height Decimal and CH shelf to bottom. My FM bolts work. Others do not, at least in my setup. I suspect a LOT of people may have issues trying to FRT with many of these bolts. In those column of heights comparisons, do you see any clue as to why that may be? (The FM bolts are thicker, and therefore more likely to cock the hammer upon recoil...) Attached File |
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