Thursday, March 27, 2014

[Mod] Swarmfire AR Delete and Flow Improvement

This is news from 2011, but I figured I would post some of the details of proper AR removal and a no-brainer flow fix for the Swarmy since these items are one of those things. You know, always overlooked, sometimes dismissed, sometimes misunderstood.

Start with the PT/AR/cylinder seal assembly. Note that the seal plate is a sort of cap, which is fit into a socket on the PT sort of like a pipe fitting. It is glued with CA glue.

Now, instinct may tell some of you to apply heat. Don't do that. No boiling. Too much risk of warping the seal plate or weakening the glue under the gasket.

Find a knife with a suitably thin and pointed blade (I use my old Swiss Army knife) and very carefully work around the entire circumference of the seal head until it can be broken loose. Try not to crack, damage or expand the socket too much.

Remove and discard the AR poppet and spring.

And here you have the seal plate. Note that the ports are almost entirely occluded by a plastic web that was used to guide the AR poppet "fingers".

And this is the most critical step, which is painfully obvious but frequently omitted for no discernable reason: Remove the webbing from the ports all the way to the edges. It is of absolute importance that you do not damage the black EVA foam gasket, or the underlying plastic of the seal plate, while doing this!
That's better.

Now, you must reinstall the seal plate on the PT. I use Devcon here, of course, but this is a low stress job and anything that can fill gaps and seal the assembly will work. Orient it correctly (match the oblong vent hole on the seal plate and the PT socket) and glue it in, making sure it is fully seated and the vent hole is plugged completely. Wipe all excess adhesive off the exterior and let cure.


Now you can test the cylinder seal install for leaks. Find the plunger, take the O-ring off, clean everything meticulously as if you were doing regular maintenance on the gun, reinstall and lube up the O-ring. I recommend white lithium grease for this seal. Run it in and out of the PT a few times to distribute the lubricant.

Note that you should NEVER put anything under the O-ring in an effort to "improve" the seal, and unless the ring is worn out, you do not need a new one.

Now you can press the seal head firmly against a smooth flat surface and give the plunger a quick push down (quick, so as to seat the floating O-ring seal). It should hit springy pneumatic resistance and if you keep pushing on it, nothing should be hissing and it shouldn't be rapidly collapsing. There should be practically zero friction from the O-ring seal. If you do not have trouble to chase here, you can proceed with the rest of the Swarmfire build. Be sure to consider the reliability mods particularly if you are going to run a high ROF or are an HvZ player, and select a worthwhile spring such as the OMW 8 kg.

Don't forget to NEVER install a plunger impact pad on Swarmfires, since the plunger does not impact the PT. The plunger's travel is stopped by the lug on the rear end of the rod and its matching track in the receiver. Most attempts (i.e. SGNerf et al.) at Swarmfire impact pads most likely don't do anything because the pad never touches the PT. If you use a thick enough pad to hit the PT at any point (like I did as a noob), you will cause major reliability problems, since the PT is free to travel forward and push on the cylinder causing excessive friction.


  1. I completed this mod guide, it's very helpful. I'm getting A+ performance from my add-on automatic with the 8 kg spring and a 3300mah 9.6v NiMh battery. Thanks for the guide!

  2. Well, I did heat one of my two tubes. Warped the hell out of the front, but managed to recover with VERY careful re-heating and reforming it.