grottulf Posted February 1, 2021 Share Posted February 1, 2021 (edited) I just got a new completely stock Foxtrot Mike FM9B. And I'm having some problems with light primer strikes. The ammo I'm using is known to have hard primers (Swedish military ammo), but they work very reliably in my Glocks, and other duty-type handguns. I'm pretty new to AR9s though. So I was thinking maybe they are picky about primers due to their firing pin spring...? I have tried bending the hammer spring as much as I could, to increase the power of the strike, but it wasn't enough. The firing pin looks good and runs freely in it's bore Any thoughts? Edited February 2, 2021 by grottulf Link to comment
Adamj Posted February 1, 2021 Share Posted February 1, 2021 Can't speak for everyone, but my GMR-15 struggled with small rifle primers. My pistols ran them just fine. Link to comment
M1A4ME Posted February 1, 2021 Share Posted February 1, 2021 both mine have standard AR15 hammer springs in them and no issues with CCI SP or SPM primers. When I got my M&P 15 5.45X39 it came with an extra power hammer spring for the hard primers in the surplus ammo. So, someone out there makes extra power hammer springs in case you find you need one of those. Link to comment
copterdrvr Posted February 2, 2021 Share Posted February 2, 2021 I have CMC triggers in all of my AR9's and they all will shoot magnum small rifle primers.... The Canik TP9SFI have is significantly modded and it won't shoot the mag rifle primers reliably but shoots the rifle primers just fine. Link to comment
jerseyglock Posted February 2, 2021 Share Posted February 2, 2021 Your trigger designed for PCC or regular AR? Link to comment
copterdrvr Posted February 2, 2021 Share Posted February 2, 2021 Don't know who the question is for but myAR 9's all have CMC pcc triggers. Link to comment
StealthyBlagga Posted February 2, 2021 Share Posted February 2, 2021 (edited) What did you do to your hammer spring? It looks like it has collapsed - if that is how you bent it, you went in the wrong direction. You know its supposed to sit on top of the trigger pin, right? Edited February 2, 2021 by StealthyBlagga Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 (edited) 2 hours ago, StealthyBlagga said: What did you do to your hammer spring? It looks like it has collapsed - if that is how you bent it, you went in the wrong direction. You know its supposed to sit on top of the trigger pin, right? Yes, as I said, I bent it to stiffen it up. Not to soften the pull, as most people do It sits on top of the trigger pin. But it was tricky to get it there, when it was bent so much. Edited February 2, 2021 by grottulf Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 (edited) Could it be a headspace issue? I don't have a feeler gauge that is narrow enough to get in there, but I'm thinking about narrowing one down so it fits... Or is there a better way to measure that? Edited February 2, 2021 by grottulf Link to comment
Bdh821 Posted February 2, 2021 Share Posted February 2, 2021 If the trigger is the issue, I recommend the Hiperfire Eclipse as those are known for extra hard smashing of primers! I set off all primers with this setup. Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 11 minutes ago, Bdh821 said: If the trigger is the issue, I recommend the Hiperfire Eclipse as those are known for extra hard smashing of primers! I set off all primers with this setup. Thanks, they are a little over my budget though. I'll try to make do with a polished stock trigger, at least to begin with. Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 I've done some more research, and I'm pretty sure it's a headspace issue. I estimate that there is roughly 0.5mm (.02") of play between the bolt and the bottom of the casing as it is now, and that can't be good. I will measure both the chamber and bolt recess (and casings) tonight to see which one is out of spec... Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 Now I've removed the barrel to get a correct measurement. I wasn't so far off in my estimation... The headspace seems to be 0.46mm (.01811") too long... Here are the numbers: Length of my 9mm ammo casing: 19.03mm (.7492") Bolt recess: 3.34 mm (.1315") Chamber depth: 16.15mm (.6358") Total headspace: 3.34+16.15= 19.49mm (.7673") Difference in length between ammo and headspace: 0.46mm (.01811") Protrusion firing pin: 0.75mm (.02953") In other words the firing pin does only poke 0.29mm (.01142") into the primer... Can anyone tell me what part or parts are out of spec? Thanks! Link to comment
grottulf Posted February 2, 2021 Author Share Posted February 2, 2021 I emailed Foxtrot Mike about it, and they were very forthcoming. They will to ship a new revised bolt to me. Great customer support! Link to comment
grottulf Posted February 18, 2021 Author Share Posted February 18, 2021 (edited) FM didn't have the required export permits, so Brownells will ship the bolt. But unfortunately, at the moment they can't export any gunparts that requires a permit over here, due to corona... So it might take a while until I get it... But I'm curious about how deep the pockets depth is in the revised FM-bolt. I asked them, but didn't get any answer. Does anyone here have one? If so, could you please measure the depth for me? Edited February 18, 2021 by grottulf Link to comment
grottulf Posted September 15, 2022 Author Share Posted September 15, 2022 (edited) Brownells still haven't solved the shipping/export problems, so I still use the old bolt. It works as long as I only use ammo with soft primers. But I'm starting to consider milling down the mating surfaces on the bolt or turning down the mating surface on the barrel, to decrease headspace... And/or buying another bolt... But I'm wondering how that would affect other things. If I mill the bolt, it will sit more towards the barrel... If I turn the surface on the barrel, I could also turn down the surface on the "ring" that mates against the upper, to compensate for that... Any ideas? I can add that I'm also having a problem now with the hiperfire-hammer (I swapped out the stock trigger), hammering the rear of the bolt, so it's become mushroomed. So I can't get the firing pin out anymore... (See pic) Considering the shape of the hiperfire hammer, I'm not really surprised that it has happened, but I'm not sure of how to fix it... Should I just grind out the problem areas, and hope it won't happen again, since the hammer won't reach it anymore? Or should I try to get the bolt to lock further to the rear (by turning down the ring on the barrel, so the barrel sits further to the rear? Or is it just crappy material in the FM-bolt, so it will solve itself with a better bolt? Any input would be appreciated Edited September 15, 2022 by grottulf Link to comment
copterdrvr Posted September 16, 2022 Share Posted September 16, 2022 (edited) I'm not sure where your are money wise, but a CMC 9mm trigger makes everything go bang....... Edited September 16, 2022 by copterdrvr Link to comment
grottulf Posted September 17, 2022 Author Share Posted September 17, 2022 8 hours ago, copterdrvr said: I'm not sure where your are money wise, but a CMC 9mm trigger makes everything go bang....... Thanks for the advice, but it's not the hiperfire trigger that causes the light primer strikes. I've already ascertained, that it's because of the headspace. It would probably not hammer the bolt as badly though, due to the hammer being flat... But I've heard of many others using hiperfire triggers in 9mm without problems. And I would very much like to be able to keep it, since it's the fastest trigger I've shot. I can shoot splits down to 0.10-0.12 with it (as long as I don't have to hit anything...) Link to comment
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