FX9 shooting out of battery

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metamatt

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Anyone else have this happen? Bunch of cases came out bulged, upon inspection even with the bolt fully forward and no obstructions in chamber cases still ejecting like that.

Wondering if this is a mixup between gen 1 and 2 parts..

Rifle is less than a year old. Pretty stumped to whats causing it if the bolt/barrel/chamber are in spec. Rifle and all parts appear to be in good condition, only thing coming out damaged is the cases
 
metamatt said:
Anyone else have this happen? Bunch of cases came out bulged, upon inspection even with the bolt fully forward and no obstructions in chamber cases still ejecting like that.

Wondering if this is a mixup between gen 1 and 2 parts..

Rifle is less than a year old. Pretty stumped to whats causing it if the bolt/barrel/chamber are in spec. Rifle and all parts appear to be in good condition, only thing coming out damaged is the cases
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Do you plan on reloading the brass? If not, then who cares what it looks like.
 
They need a stiffer spring and/or a much heavier buffer than the lightweight POS garbage they come with.
LMAO, I walked out of the indoor range with my stock buffer (CSC) to see if the store had something heavier (major FTE and double feed issues) and the guy at the counter didn't believe me that the featherweight POS came out of a blowback FX9. Took a brand new one right off the shelf to see for himself, and he couldn't believe it. One of the owners overheard us and came over, first words out of his mouth was "that isn't right". Never had OOB issues with the one I had, but the rifle length spring and 5.4oz Odin buffer instantly cured all its issues. Guys here have put the 7.X oz Odin buffer in theirs with great success.
 
Unholysavage said:
They need a stiffer spring and/or a much heavier buffer than the lightweight POS garbage they come with.
LMAO, I walked out of the indoor range with my stock buffer (CSC) to see if the store had something heavier (major FTE and double feed issues) and the guy at the counter didn't believe me that the featherweight POS came out of a blowback FX9. Took a brand new one right off the shelf to see for himself, and he couldn't believe it. One of the owners overheard us and came over, first words out of his mouth was "that isn't right". Never had OOB issues with the one I had, but the rifle length spring and 5.4oz Odin buffer instantly cured all its issues. Guys here have put the 7.X oz Odin buffer in theirs with great success.
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Forgot I put heavier buffer in mine also.It was the Odin adjustable one for 9mm.:slap:
 
This buffer thingy in FX-9 is a mystery for me. I mean their engineers have designed a new gun, which is a 9mm blowback. Great! Obviously they must have a knowledge of how the blowback system works.

The gun science tells that the optimal total mass of the bolt and all metal chunks attached to it must be around 21 oz for the 9mm carbine barrel in order to keep the casing chambered until the bullet leaves the barrel. FX-9 bolt itself is 11.5 oz - at least in my own FX-9. And the buffer appears to be a standard AR-15 which is in my case is 3.2 oz. Like WTF, the AR-15 9mm has a bolt around 15 oz and it has a 9mm-specific buffer or H3 buffer around 5.5 oz. Which brings it about into that optimal weight of 21oz - sounds right. But FX-9 has a pathetic 14.8 oz in total. And from what it looks - there is a standard AR-15 spring and no spacers. It's like you shoot 9mm round out of Ar-15 223 without bolt lock mechanism.

What's really strange: The buffer of FX-9 - is probably the only area which shares original AR-15 mechanical parts. Lots of it on the market. I just don't understand why FX-9 is still using a standard AR-15 buffer while they could easily source a heavier 9mm buffer or separate weights, and so produce a reliable carbine without a hassle. Sure, heavier buffer would cost around $20 more for those tungsten weights. But that's not where $20 can be saved when it comes to reliability. It's been like 3 years since it hit the market and still having these stupid issues.

Nevertheless, I'm happy I own this gun in today's Canada still. It's a nice gadget for it's price. Yeah, I've eventually modded it with a heavier buffer. You don't need to order Odin or other adjustable fancy buffers with convenient screws and bunch of weighs most of which will never be used. Leave it for snowflakes with two left hangs out of their a$$ who scared to drive out roll pin using a cheap punch set from a dollar store. Instead, just buy a three separate tungsten weights and replace some or all of those original three steel weights in the stock buffer simply by removing a roll pin. Basically you can convert the stock FX-9 buffer to H1, H2, H3 buffers using combination of steel/tungsten and find your own sweet spot. It's set-and-forget thing for the given gun once you figured it out, so don't waste money for adjustable buffers which you adjust 1-2 times in their lifetime.
 
serg777 said:
The gun science tells that the optimal total mass of the bolt and all metal chunks attached to it must be around 21 oz for the 9mm carbine barrel in order to keep the casing chambered until the bullet leaves the barrel. FX-9 bolt itself is 11.5 oz - at least in my own FX-9. And the buffer appears to be a standard AR-15 which is in my case is 3.2 oz. Like WTF, the AR-15 9mm has a bolt around 15 oz and it has a 9mm-specific buffer or H3 buffer around 5.5 oz. Which brings it about into that optimal weight of 21oz - sounds right. But FX-9 has a pathetic 14.8 oz in total. And from what it looks - there is a standard AR-15 spring and no spacers. It's like you shoot 9mm round out of Ar-15 223 without bolt lock mechanism.
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This is interesting stuff about the weights, thank you, it contributes to my understanding of 9mm PCC dynamics overall. In the case of my TNW ASR in 9mm, the stock recoiling weight (not counting the spring itself) between bolt and buffer weight was 26oz. If the ideal for a 9mm blowback carbine is around 21oz, that means TNW put in an extra 5oz. That would explain a lot about why so many users have FTE problems with at least some cartridges - insufficient power to drive the heavier mass far enough back to completely cycle the action, with brass sometimes getting hung up sideways, sometimes diagonally, or sometimes clearing but then the next round getting jammed diagonally as the bolt hasn't quite gone far enough backward.

In mine I had some of these events and so tried clipping the spring, a half-coil at a time, which resolved most of the problem at around 2.5 turns of the stock spring shortened. But I didn't like how dirty the action got with this earlier cycling, too much soot in relatively few shots. So I drilled out the buffer weight and added a tungsten rod 16mm diameter x 42mm long and swapped the spring for a Strike Industries AR flat wire spring - very long and with almost constant compression instead of the steadily increasing compression weight of the stock spring. The result due to the 1.75oz increase, to 27.75oz total weight being pushed back, as well as the slightly higher initial spring force compared to stock, was a slightly longer delay in 'uncorking' but then a smooth opening of the bolt which gave clean ejection and loading of the next round. I made these changes with 147gr in mind specifically. Would likely have done it a bit differently for lower mass bullets, probably not adding weight and maybe even reducing it a little if ejection proved still to be an issue after putting in the better spring.

The FX-9 seems a rather nice carbine. Seems for the most part it's a keeper. Be a shame if anyone gave up on it without minor changes to see if it could be improved. I wonder about the thread title, referring to 'shooting out of battery.' Is that really the case, that it's firing rounds before the bolt is closed? Seems doubtful. More likely premature bolt opening while the powder is still expanding the brass. I'd go for a heavier bolt, somehow adding mass, even if it means drilling out steel and replacing it with heavier tungsten. It's a pity we can't add something like roller-delayed blowback... but that would be quite a feat of engineering once a gun has been built.
 
Back when the FX9 first showed up H3 buffers weren't easy to find. I got my Odin adjustable/H3 because it was in stock at CSC, where the rifle was being a jammomatic POS at the time LOL.
My opinion - 5.4oz is the lightest I would go for one of these rifles. My FTE stopped at around 4.2oz during testing, but at 5.4oz it's still harsher than a JRC 9mm. One guy here tried the 9mm PCC Odin buffer at its max 7.4oz, and everything he put through his still cycled fine. If I were to do it again I'd go heavier than a H3, which limits our options up here.
Edit: looks like Cowboy Tactical sells a 9mm heavy AR buffer, no weight listed but it could be a good cheap option to try.
 
Unholysavage said:
Back when the FX9 first showed up H3 buffers weren't easy to find. I got my Odin adjustable/H3 because it was in stock at CSC, where the rifle was being a jammomatic POS at the time LOL.
My opinion - 5.4oz is the lightest I would go for one of these rifles. My FTE stopped at around 4.2oz during testing, but at 5.4oz it's still harsher than a JRC 9mm. One guy here tried the 9mm PCC Odin buffer at its max 7.4oz, and everything he put through his still cycled fine. If I were to do it again I'd go heavier than a H3, which limits our options up here.
Edit: looks like Cowboy Tactical sells a 9mm heavy AR buffer, no weight listed but it could be a good cheap option to try.
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Normally stock AR-15 9mm buffer is around 5-5.5 oz. When I inserted 3 tungsten weighs into FX-9 original buffer it comes to about 6.2 oz. This is even slightly more than H3, it already brings FX into comfort zone, but I guess FX buffer deserves even more weight because they have lighter bolt. The casing of the FX buffer is aluminum, so if there would be steel - it would get more weight to it, with three tungsten probably would be about 8 oz.

Still baffles me why FX continues utilizing the lightest AR buffer in a blowback carbine with even lighter bolt while people yelling about this issue from the roofs. It's like soviet Lada car - it never runs right from the factory, you buy it and immediately start improving and modifying it to bring it to working condition, while same model remains on conveyor for decades without changes. But once you did it - you will love it.
 
I agree, right from the factory the fx-9 should have come with a 9 oz extended length buffer, limiting the bolts rearward travel to just 1/4” past the bolt hold open. This IMO was the best upgrade that I did
 
So what’s the consensus.? What weight should be a good all around and where might one buy such a thing...? No being lazy. Just asking
 
serg777 said:
You don't need to order Odin or other adjustable fancy buffers with convenient screws and bunch of weighs most of which will never be used. Leave it for snowflakes with two left hangs out of their a$$ who scared to drive out roll pin using a cheap punch set from a dollar store. Instead, just buy a three separate tungsten weights and replace some or all of those original three steel weights in the stock buffer simply by removing a roll pin. Basically you can convert the stock FX-9 buffer to H1, H2, H3 buffers using combination of steel/tungsten and find your own sweet spot. It's set-and-forget thing for the given gun once you figured it out, so don't waste money for adjustable buffers which you adjust 1-2 times in their lifetime.
Click to expand...

Well damn... I actually had no idea you could do that. Never managed to build an AR before they got prohib so all I have is my FX-9 and I never thought to pop out the roll pin and see if there were removable weights in the stock buffer. Kinda glad I never got around to replacing the buffer with one of the expensive adjustable ones. I did replace the stock buffer spring with a strike industries flat wire one and that solved my FTF issues along with lots of oil when I was still breaking the gun in. The more you know I guess.
 
SurplusShenanigans said:
Well damn... I actually had no idea you could do that. Never managed to build an AR before they got prohib so all I have is my FX-9 and I never thought to pop out the roll pin and see if there were removable weights in the stock buffer. Kinda glad I never got around to replacing the buffer with one of the expensive adjustable ones. I did replace the stock buffer spring with a strike industries flat wire one and that solved my FTF issues along with lots of oil when I was still breaking the gun in. The more you know I guess.
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Flat wire spring might not fit over the buffer shoulder (little bump almost at the end of buffer) because its internal diameter is 0.75" whereas the buffer shoulder external diameter is 0.78". You might end up with spring sitting on the shoulder. I guess after couple shoots it will press in. Anyways, I opted it out. Instead, like other folks suggested, put an insert to the bottom of the buffer tube. It does two good things:
- increase the force of the spring, as it becomes a bit more squished. Basically you will achieve same effect as +10% spring usingf the original stock spring
- it decreases the rearward travel of the bolt. This is common practice in AR-9 builds to prevent bolt overtravel and slamming against the bolt stop with high speed. The optimal gap between bolt stop and farthest bolt position should be about 3/16" - 1/4". On FX-9 it is probably around 3/4". So 7-8 25c coins will make it. Or might get the plastic insert specially designed for this.
 
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