Here's a Part I of my BASIC guide to keeping your prized AEG(s) in tip top shape for blasting those dirty OPFORs on the field.
Checking Cylinder Compression
in your Airsoft AEG
First, do a Chronograph test - Record your results in a log for future reference (If you don't have a chrono, borrow your buddy's or take your AEG (in a case, nimrod) to your local shop and ask them to fire 10 shots. Write down the results, if you can. That should be enough to give you an idea of what's going on with the FPS). Do this BEFORE taking the gun apart so that you can compare those results with the results you get after you clean things up inside the gun to see if you helped or hindered performance.
If shooting consistently and the velocity has not decreased since the date of upgrade installs/tuning mods, then consider leaving your AEG alone.
If not, disassemble the gun to access the gearbox.
Watch the following video. I had to cut the first part completely out because I stumbled over my words too much, like a blithering idiot. I was rambling a bit as well. So I just cut the crap and went right to the good stuff. Also, you don't need to do this test using the Air Nozzle, like I did. It really doesn't make that much of a difference because of the way the test must be performed.
If it's easy to press the piston down while you've sealed off the cylinder head/air nozzle port, then you've got a compression issue that needs to be resolved.
- Inspect piston head o-ring for deterioration/cracks/wear & tear. Make sure the o-ring is not so big that it creates too much friction against the cylinder and drops your velocity.
- Wrap or re-wrap the cylinder head o-ring(s) seal(s) with Teflon Tape. (at least 3 or 4 complete wraps, minimum). Make sure it's a very snug fit when you insert the cylinder head back into the cylinder.
- If the piston head has air intake vents or port holes on its face, then check to make sure there is nothing obstructing their openings (e.g. excess grease, dirt, debris, etc).
- Apply PTFE/Teflon grease to the inside of the air nozzle.
You'll need to make sure you do this carefully and correctly, otherwise you'll end up making an absolute mess inside your gun's hop-up and inner barrel.
- Basically, I take a q-tip and dip it in my Fuch's white lithium grease with PTFE thickener.
- Apply just a little bit of that grease using the q-tip to the inside of the air nozzle.
- Slip the air nozzle back onto the cylinder head nozzle and slide the nozzle up and down a few times to spread the grease around.
What you hope to accomplish is to utilize not only the lubrication characteristics of the grease to allow the air nozzle freedom of movement along the cylinder head nozzle, but also its ability to create an air seal , thanks to the PTFE/Teflon additive in the grease. This air seal serves to keep air from escaping of out the back of the air nozzle, maximizing the volume of air that is then used to propel the BB towards an unlucky victim on the field.
Now, the most important part of this process is use something thin enough to swab out any excess grease from the cylinder head & air nozzles.
- Once you've done this and have completed every other task requiring the gearbox to be open, put the gearbox back together, including attachment of the motor.
- Do not assemble the gun all the way. Just enough so that you can plug a battery in and shoot the gun without the barrel assembly attached.
- You'll need to dry-fire the gun/gearbox a few times to get any excess grease out of the cylinder head/air nozzle by using the puff of air produced that normally propels the BB out of the gun.
- While firing, don't point the gun at anything you don't want grease to get on.
- Wipe off any excess grease that doesn't get blown completely out.
If you forget this step, and go straight to reassembling your AEG, it's likely that you're going to make a mess inside your hop-up & inner barrel.
Put the gun back together. Chrono. Record your results. They should improve. If not: it's your fault. If they DID improve: it's my fault. You can direct your thank you notes to the comments section of the blog here. You're welcome.
Disclaimer: There's more than one way to skin a cat. As such, if you have what you consider to be better methods for improving compression, then by all means, share that wealth of knowledge with all three of us here on the blog. Post it up in the comments section, or email me the details and I'll post them up as an addendum to this blog entry, giving you full credit, of course.