Foxtrot Mike FM9 Slam Fire

[LorinB]

Has anyone else had a slam fire or multiple round burp out of an FM9?  The bolt they use has a smaller diameter firing pin channel and firing pin retaining spring than the Taccom and Kaw Valley that I have to compare.  They sent me another pin and spring then another complete BCG and all allow the firing pin to dimple a Federal primer when bolt drops.  Their firing pin retaining spring is similar to the spring in a ball point pen and about 1/3 as stiff as the Taccom or Kaw Valley and the firing pin channel in their bolt is to narrower to use a larger spring.

[grottulf]

Yes, I'm having issues with intermittent 2-3 round bursts with my FM9.

I just assumed it was trigger related, and since I'm planning on swapping out the stock trigger, I didn't look into it more thoroughly...

Is there a way to tell if it's because of a week firing pin spring, or if it's trigger related?

 

 

[RaylanGivens]

I purchased an FM9 bolt several months ago...  Had trouble with the firing pin jamming...  Sort of the opposite problem you two are having...  Called FM and sent it back to them...  Received a completely different updated bolt...  The new bolt still has the small ball point pen style firing pen spring...  Not sure why FM uses a non-standard firing pin spring...  or why they don't machine the bolt internals to take the standard size springs...  I'm using the replacement bolt and no issues so far.

 

I've heard that @Maxamundouses FM9 bolts and he doesn't seem to have any trouble with them...

[RaylanGivens]

1 minute ago, RaylanGivens said:

I purchased an FM9 bolt several months ago...  Had trouble with the firing pin jamming...  Sort of the opposite problem you two are having...  Called FM and sent it back to them...  Received a completely different updated bolt...  The new bolt still has the small ball point pen style firing pen spring...  Not sure why FM uses a non-standard firing pin spring...  or why they don't machine the bolt internals to take the standard size springs...  I'm using the replacement bolt and no issues so far.

 

I've heard that @Maxamundouses FM9 bolts and he doesn't seem to have any trouble with them...  He might have someone machine the bolt internals to take a standard, stronger firing pin spring?

 

[Dirty_J]

On 6/1/2021 at 11:57 PM, RaylanGivens said:

I purchased an FM9 bolt several months ago...  Had trouble with the firing pin jamming...  Sort of the opposite problem you two are having...  Called FM and sent it back to them...  Received a completely different updated bolt...  The new bolt still has the small ball point pen style firing pen spring...  Not sure why FM uses a non-standard firing pin spring...  or why they don't machine the bolt internals to take the standard size springs...  I'm using the replacement bolt and no issues so far.

 

I've heard that @Maxamundouses FM9 bolts and he doesn't seem to have any trouble with them...

I’m pretty sure he’s running a modded Stern Defense bolt. 

[Ccampo1129]

Try to avoid anything Foxtrot Mike. Myself and 2 buddies have had nothing but issues out of them. I will say they do have great customer service! Refunded me in full, no questions asked!

[PCCinator]

I, too, am having issues with an FM PCC. I bought the upper and lower separately. I had a couple of bursts today that seemed full auto, or maybe it's just my finger double tapping or triple tapping . Sure seemed like full auto and scared the *&%$#@! outta me as I hit the target hanger like some noob.  I wanted to blame the new trigger; I dropped in a 3.5lbs Triggertech AR-9 this weekend, but it's not adjustable; thinking of sending it back and eating the restock. But now that I am seeing this burst issue with other people and FM's, hmm.

 

The FM is VERY finicky with ammo. None of my target reloads feed right. I guess you have to run just hot ammo (it does say that to run over 1100fps in the manual, that of course I didn't read until after I bought the lower).

 

Also not a fan of the side charging handle. Not a natural action charging that thing.

 

Wish I'd just bought a CMMG. Live and learn!

Edited June 28, 2021 by PCCinator

[Walli]

I owned a FM lower, complete upper and barrel. The only part I still own is the lower. From my experience with the FM parts, I would stay away from anything FM made with the exception of the their 9mm lower receivers. Sad but true.

[RangerTrace]

I tried one and it was junk.

[grottulf]

17 hours ago, PCCinator said:

I, too, am having issues with an FM PCC. I bought the upper and lower separately. I had a couple of bursts today that seemed full auto, or maybe it's just my finger double tapping or triple tapping . Sure seemed like full auto and scared the *&%$#@! outta me as I hit the target hanger like some noob.  I wanted to blame the new trigger; I dropped in a 3.5lbs Triggertech AR-9 this weekend, but it's not adjustable; thinking of sending it back and eating the restock. But now that I am seeing this burst issue with other people and FM's, hmm.

 

The FM is VERY finicky with ammo. None of my target reloads feed right. I guess you have to run just hot ammo (it does say that to run over 1100fps in the manual, that of course I didn't read until after I bought the lower).

 

Also not a fan of the side charging handle. Not a natural action charging that thing.

 

Wish I'd just bought a CMMG. Live and learn!

My problem was probably self inflicted...

I had limited the over travel on the stock trigger.

After I restored it to factory condition, I haven't had any issues.

I haven't shot it enough after that, to say for sure though. 

But I'll get back to you if it starts  again.

 

[grottulf]

I should add that I have never had a single failure to feed with mine.

 I've only shot FMJ with it, and about 600 rounds so far though.

I have however some problems with failure to fire, but I traced the cause of that to a too long headspace.

And they will ship a new bolt to me, when Brownells finally gets their thumbs out of their ass...

[grottulf]

Now I've shot a few hundred rounds at a competition this weekend, and I never had any slamfire.

So I'd say my problem was due to my trigger modifications.

[Ned Christiansen]

I've seen several 9mm AR carbines now that do this. The problem is that the 9mm round is so short, and so the stroke needed to pick up the next round is also short, but the bolt movement needed to properly function the FCG is long. If the bolt doesn't get a full-strength impulse moving it back, it goes back far enough to eject and feed but not far enough to get the hammer hooked on the disconnect. The result is burst fire. The ones I've seen doing this were very dirty and dry and the owners said the guns had not done it before. Lube made it go away in these cases but it could just as easily be caused by changing to a milder load or having too much buffer spring in the gun.

 

I have not done a deep study as I don't own an AR in 9mm but I'm a little surprised some company has not addressed this with a different bolt and/or hammer profile. Very likely someone has and I just don't know it.

[PCCinator]

This has nothing to do with the trigger or the recoil impulse. LorinB has explained the problem well, which I confirmed this weekend: The firing pin spring is too small and weak to retain the firing pin upon bolt close, and this allows the pin to light strike, and in some cases discharge a round. An EXTREMELY dangerous design flaw. He's how I tested it: I have a few thousand primed cases (I'm a handloader). Twice, I put a primed case into the chamber. Then I let the bolt close. As you can see from the photos, in both cases, the primer was dimpled.

 

This is a design flaw, pure and simple. This gun is not safe. I contacted Foxtrot Mike on Friday 7/2 about this, but they didn't get back to me.

 

Edited July 4, 2021 by PCCinator

[Dirty_J]

Hope you don’t ever inspect a 5.56 milspec gun 

[Ner]

can confirm a Slamfire caused by a weak firing pin spring

Edited July 6, 2021 by Ner

[Ned Christiansen]

Those dimples are actually less that what is "standard" with an AR15 on unfired, ejected rounds, but-- of course in 9mm we're working with pistol primers which are easier to fire. And I don't at all doubt that some slamfires are caused by firing pin inertia, but for sure some doubles  / burst fire is also cause by the bolt not cycling back far enough to hook the hammer on the disconnector.

[PCCinator]

Any gun that fires without pulling the trigger in the 21st Century is dangerous and defective.

[Ned Christiansen]

In any of the above cases one might chalk it up to manufacturers not doing their homework.

[Ner]

• cleaning + oiling the right spots on the bolt 

• avoiding low pf + weared off trigger group/replacing a littlef*#ker disconnector spring once a year

• replacing trigger pin + spring twice a year

 

as i see how to battle slamming

[PCCinator]

Just FYI, Foxtrot Mike is giving me a full refund, and I bought both the upper and lower from Brownells. I'm going to give them some credit for stepping up.