Post by Stinger on Mar 27, 2014 8:07:25 GMT -5
So I was playing airsoft on Saturday with my Airsoft G.I. FMG4-A1 Hard Next-Gen. Everything was fine. It had previously been chrono'd at 405 FPS with 0.2-gram BBs. After the session finished, I went home and started to clean everything because it had been muddy and wet outside. When putting it back together, the hop-up unit seemed to go in a bit weird. Normally, it sits in place and a spring keeps it pushed back (to seal against the air nozzle). When I put it back together, it kind of just stuck there and the spring wouldn't move it. I was a bit pressed for time, so I seated it as best I could and closed everything up.
Just last night, I wanted to chrono my gun with 0.25-gram BBs. I set up my chrono, loaded the gun, and fired...205 FPS. So I thought, "Hmmm...that's weird..." and fired again. 275 FPS, "Okay, kinda scared now." 260 FPS
So I started troubleshooting, knowing I shouldn't have lost that much FPS from 0.05 more grams of BB being fired. My guess was that it was an airseal, and I was right. I remembered the hop-up issue, and I started experimenting. I pulled the large spring off of my brother's XCR-C, which serves the same purpose as the small spring on my hop-up. His just goes around the inner barrel in front of the hop-up unit. With that in my gun, it shot fine at 370 FPS. That spring was powerful enough to push the hop-up unit back.
My issue is that I can't figure out what changed. I know what's wrong, but I don't know why it's wrong. Something on my hop-up is sticking in place in the upper receiver. I suspect that it's the C-clip, because it seems to fit better without that in. However, nothing on the C-clip has changed. It fits on properly, and is exactly the same way it was before.
Any ideas?
Most of the gun is stock internally right now. The inner barrel is a MadBull Black Python VII 6.03mm, 455mm.
Before all of this happened, I ordered a ProWin unit which should arrive on Monday. I had been having other unrelated hop-up malfunctions, and I wanted a better one. I'm hoping that the ProWin may simply fit better, but it still bothers me that the stock unit fit fine one moment and didn't the next.
UPDATE EDIT:
Okay, so it suddenly doesn't bind up anymore. I was messing around with the hop-up and determined that the C-clip was causing the binding issue. However, I put the C-clip on after testing that and suddenly, it fit in the upper receiver fine. I have no idea what I did. It just fit.
Then I noticed that, while it fits and does not bind up, the spring on the hop-up has some issue. It's as if it got shorter or less powerful. I can push the unit in as far as it will go until it stops, and the spring doesn't even seem to contact the piece on the upper receiver that it pushes against. I don't know what could have caused this. Everything looks normal. This is something that I'm hoping the new unit will fix.
In the meantime, I took a piece of rubber tubing large enough to fill the gap that that the spring goes into but small enough that the spring won't slide into it, and I set that into where the spring connects on the upper receiver. It's essentially a little spacer. Now, the spring pushes back perfectly fine.
It's Chrono'ing at 373.9 FPS with 0.25-gram G&G BBs. So I fixed the problem. In fact, I think the air seal is even better than it was before all of this happened because I have far better consistency now. Before, I had +/- about 8 FPS. Now, I have +/- 2 FPS at the most.
The only thing I still wonder about is why I need that spacer now. I would understand if it was a new hop-up unit going into my gun, since parts sometimes need some "professional" fitting
, but this is the stock unit that came with the gun. It was perfectly fine before. What changed?
Just last night, I wanted to chrono my gun with 0.25-gram BBs. I set up my chrono, loaded the gun, and fired...205 FPS. So I thought, "Hmmm...that's weird..." and fired again. 275 FPS, "Okay, kinda scared now." 260 FPS
So I started troubleshooting, knowing I shouldn't have lost that much FPS from 0.05 more grams of BB being fired. My guess was that it was an airseal, and I was right. I remembered the hop-up issue, and I started experimenting. I pulled the large spring off of my brother's XCR-C, which serves the same purpose as the small spring on my hop-up. His just goes around the inner barrel in front of the hop-up unit. With that in my gun, it shot fine at 370 FPS. That spring was powerful enough to push the hop-up unit back.
My issue is that I can't figure out what changed. I know what's wrong, but I don't know why it's wrong. Something on my hop-up is sticking in place in the upper receiver. I suspect that it's the C-clip, because it seems to fit better without that in. However, nothing on the C-clip has changed. It fits on properly, and is exactly the same way it was before.
Any ideas?
Most of the gun is stock internally right now. The inner barrel is a MadBull Black Python VII 6.03mm, 455mm.
Before all of this happened, I ordered a ProWin unit which should arrive on Monday. I had been having other unrelated hop-up malfunctions, and I wanted a better one. I'm hoping that the ProWin may simply fit better, but it still bothers me that the stock unit fit fine one moment and didn't the next.
UPDATE EDIT:
Okay, so it suddenly doesn't bind up anymore. I was messing around with the hop-up and determined that the C-clip was causing the binding issue. However, I put the C-clip on after testing that and suddenly, it fit in the upper receiver fine. I have no idea what I did. It just fit.
Then I noticed that, while it fits and does not bind up, the spring on the hop-up has some issue. It's as if it got shorter or less powerful. I can push the unit in as far as it will go until it stops, and the spring doesn't even seem to contact the piece on the upper receiver that it pushes against. I don't know what could have caused this. Everything looks normal. This is something that I'm hoping the new unit will fix.
In the meantime, I took a piece of rubber tubing large enough to fill the gap that that the spring goes into but small enough that the spring won't slide into it, and I set that into where the spring connects on the upper receiver. It's essentially a little spacer. Now, the spring pushes back perfectly fine.
It's Chrono'ing at 373.9 FPS with 0.25-gram G&G BBs. So I fixed the problem. In fact, I think the air seal is even better than it was before all of this happened because I have far better consistency now. Before, I had +/- about 8 FPS. Now, I have +/- 2 FPS at the most.
The only thing I still wonder about is why I need that spacer now. I would understand if it was a new hop-up unit going into my gun, since parts sometimes need some "professional" fitting
, but this is the stock unit that came with the gun. It was perfectly fine before. What changed?