FN15 pistol w/ Dead Air Nomad-L sub problems

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lightfall
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FN15 pistol w/ Dead Air Nomad-L sub problems

Post by lightfall »

I have a stock FN15 Pistol (fixed pistol length gas system with 12" barrel, I think a standard buffer spring and weight in the factory configuration) with a Dead Air Nomad-L suppressor. When using various factory subs (S&B, Remington, Fiocchi, 200-220 gr) it will frequently not load the next round, or will half-load the round whereby the bolt is pinching a round that is not in the chamber.

I am new to firearms, suppressors, and this cartridge so I am not sure what the recommended trouble shooting process should be or if there are any suggestions on how to remedy the problem? Your advice is much appreciated.

https://fnamerica.com/products/disconti ... l-300-blk/

https://deadairsilencers.com/silencers/nomad-l/
Tugnut
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Re: FN15 pistol w/ Dead Air Nomad-L sub problems

Post by Tugnut »

Sounds undergassed. You may need to pull the gas block and slightly enlarge the gas port.

But first, which mags are you using? I'd make sure you're using 300blk-specific Magpul or Lancer mags. The bigger 30 cal bullets don't always play nice with standard 556 mags.
lightfall
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Re: FN15 pistol w/ Dead Air Nomad-L sub problems

Post by lightfall »

I tried a variety of mags including magpul 556 and magpul 300blk as well as a couple metal ones. It seemed to occur with all of them. At first I thought maybe this was the issue since I had the magpul 556 but it did it with the 300blk one as well.

Given my lack of experience what is the reasoning for the undergassed aspect as the causative mechanism? Is it that the bolt is going back not far enough? Or is the bolt going back too aggressively or fast?

I assumed when FN made this with the short barrel in 300blk that it would be setup for suppressor use with subsonic rounds. Is there a guide on how to pull a gas block and enlarge it? Forgive my inexperience.
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dellet
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Re: FN15 pistol w/ Dead Air Nomad-L sub problems

Post by dellet »

Before doing anything else, lube everything that moves generously, wait for at least 200 rounds or. Y or it by hand that many times.

At some point or multiple times, make sure the gas tube is clear. Low compressed air or something like brake cleaner through the tube. Not uncommon on new barrels to shave a bit of copper off the bullets and restrict the gas flow.
300 Blackout, not just for sub-sonics.
BJK
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Re: FN15 pistol w/ Dead Air Nomad-L sub problems

Post by BJK »

Since you're new to firearms you're pretty much limited in what you might be capable of. The 300BLK is a reloaders dream, but since you don't reload you're pretty much at the mercy of the factories. Not all subs will function in every firearm. From what I've been reading S&B subs are notorious for not functioning a semi-auto and lots of folks say it doesn't work in their ARs. Maybe they're intended for actions other than semi? I don't have the answer to that. I know they won't function in mine either, but I knew before buying any parts that I was going to reload to make my ammo work in my gun rather than make a gun with variables and change the gun to suit the ammo. My memory just isn't that good to remember settings for each load. But I can keep notes at the load bench and once the ammo is made to my spec' it's good to go.

If after trying the lube suggestion if it still doesn't function 100% you might want to try various subsonic loads to find the ones that will work, stick to them, and forget the others. Stock up on what works.

You didn't mention supers, I'll assume they work fine since it would be a really lousy 300BLK that won't function with them.

I recently bought what I could find locally (subs) to test in my gun and the one subsonic load that I found that works for me in my 10" build is made by AMMO Inc and is their /stelTH/ load (not a typo) that is designed for use with suppressors. I'd give you the velocity and such from the box, but again, IMO that's really meaningless w/o knowing about the test barrel and such. As with lots of factory 300BLK ammo it's expensive. I paid $1.50/round. Yeah, that's another reason I handload.
lightfall
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Re: FN15 pistol w/ Dead Air Nomad-L sub problems

Post by lightfall »

Thank you for the advice everyone. I finally had a chance to do some more trouble shooting. I tore everything down to clean again, checked the gas port (no leaks from what I can tell), made sure that was open, and then I lubed it like crazy. I also cycled the bolt a few hundred times.

Now using the pmag 300blk mag and supers it cycles fine still, makes quite a bit of smoke but no big deal. Winchester 200gr subs now cycling and locking the bolt back on the last round apparently, but S&B cycle and do NOT hold the bolt open. I took a slo-mo video and it looks like I am ejecting around 3-4 o'clock for supers and subs suppressed.

I gather that for whatever reason the S&B subs suppressed do not have the juice to reliably get the bolt all the way back to lock last round but it has improved enough with the lube and cycling that it seems to be feeding reliably.

I purchased a sprinco yellow spring and an adjustable buffer weight. I am going to swap my standard spring for this yellow spring and see if that changes things, if that does not produce reliable lock back I will slightly lighten the buffer as well in the hopes that tunes it where it needs to be. My intention is to use this rifle primarily with subs suppressed with an option to use supers swapping a mag in a pinch.

Any other feedback on what seems to be the best overall subsonic round?
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