I have a sendra arms M-16 lower which always worked well with 5.56 for 30 years about 4 years ago I bought FM-9 belt fed upper receiver it has never been able to fire more then one round. What it looks like to me is a feed problem where the belt binds in the feed tray. I lock the side back open the top cover line up a cartridge with the barrel so the bolt can strip a round when it closes. Close the top cover and let the bolt go and I'm able to fire that one round. When the bolt retracts the belt binds and does not align the next round.

I'm not even able to feed the belt manually to me I should be able to cycle this thing manually. I shipped the upper to FO a few months ago it had a broken firing pin they repaired it sent me a video of it working with their FA lower. They are saying the issue could be my lower buffer tube hole is was not machined centered correctly. That could be the case it's a Sendra arms was never a high end lower, but even if I remove the stock and buffer tube I'm still not able to advance the belt correctly it still binding.  I can't see how it's the buffer tube issue I should be able to manually feed rounds.

With the lid open and feed tray also open when I put the belt in there move the feed paws manually with my finger it seems like the tray area is too small for the links I have. I know they have a Generation 2 now mine is a Generation 1

My question is  if you have one of these are you able to manually feed rounds with the charging handle and how much resistance is there. Maybe this is normal not able to manually cycle rounds from the belt while firing it the force of the blow back is able to cycle it.

FO wanted me to ship my registered lower to them, but I rather not do that if I can figure out another way to resolve this.

I think I'm one of the first to get one of these.  I had some issues and sent it back and they supposedly replaced the parts to make mine a Gen 2.  I initially tried running it dry as a break in and it wasn't reliable.  I found that if I just lube the track in the top cover, it is very reliable.  
I'm running the same buffer/tube and spring setup that I run in my CMMG RDB and get a really nice cyclic rate of around 450 RPM.

I don't recall bothering to hand cycle it as I think as you said, it does need a considerable amount of forward energy to strip the rounds off the links.  I'll try to do that for you next time I take it out...which will probably be a while these days...

Did the company stop making these? I don't see any for sale anywhere?

I spoke to Michael he is the gunsmith maybe the owner not sure a few weeks ago as far as I know they are still in business seem to be out of stock. I don't think they sold that many the cost of $2500 only customer really was going to be someone with a Full auto lower how people around have those. If your well off enough to buy one last 10 years probably well off enough to just buy .223 what ever the cost which always works well.

I found out that it's not really possible to manually cycle rounds because the short stroke of the top cover places lot of force on the bolt. He said that the Gen2 changes was an attempt to resolve that because people complained lot about it. I did tell him that when I remove the buffer spring I'm able to slide the bolt back into the buffer tube with out issue he seemed to think that verified the issue wasn't with the buffer tube. One thing I did notice was the difference between the AR-15 and M-16 hammers the AR-15 has a notch at the top of the hammer the bolt slides little easier over it.
After playing around with it I was able to get it to fire on a Bushmaster semi auto lower receiver with Tulammo. It still jammed a few times but seemed to be getting better as I fired it. With Tulammo after I fired some rounds to work in semi-auto on my FA Sendra lower not in full-auto, but that could be the auto seer. I have a few of those I can adjust them as needed which I have before for a .22 conversion I have.  

Overall if I had to do this again spending $2500 would have just gone with a regular 9mm Mag conversion. Loading links sucks can load up lot of mags for the same effort cheaper to buy and belt feeds are finicky anyway.

Now I can't get anymore Tulammo all sold out I sent email last week to FO asking if wolf work the same never got a reply I'm sure they are busy.  If I can't get it working in next few weeks with some hot reloads I made probably going to sell this just go with stern defense mag well conversion.

I haven't had mine out for a while but once broken in for a few hundred rounds it was reliable. I found that I had to shim the upper to lower fit as the bolt hit the buffer tube. I have many uppers and this is a first. It is a lot of extra work with the belts, picking up links with a magnet etc but it does scratch the belt fed itch for cheap.
Attached File


Attached File