Swelled hopup rubber
 

Ok, here's the problem. My KSC G17 hopup rubber is swelled up from silicone oil. Even on the lowest setting BBs arc straight up after 15ft. I tried, as suggested in an old thread, to soak it in dish-soap, but it didn't work. Is there anything else I can try? At this point I'll try anything. I'd just get a new one, but all group orders for parts are at-least a month away, and I really want my gun working now!

perhaps drying it up a bit using a blow dryer? I don't know if it'll help though.

if you manage to source a smaller ball bearing for the hop up, use that in the meantime

if not, you can break out the file and a dremel bit

http://gungineer.cande.biz/gas_custom/gas_oni.htm

I suggest the smaller ball bearing as it is easily reversible

So the less the hopup bucking pushes on the bb, the less hopup?

Because even completely removing the ball bearing dosent help..

Soak the rubber in some isopropyl alcohol (NOT rubbing alcohol as it contains oils as well). It will dry the rubber out significantly. Then put it back in the chamber and use silicone oil very sparingly. If you use green gas, you NEVER need to add any extra to the gun.

If you use propane, well, then you need to add some every few mags or so.

There's ZERO need to get out a Dremel or modify anything.

I did not know that. That's excellent advice and will help many others if it works.

ooh
thats excellent
disregard my post

Wow, I wouldn't have thought of that either. Thanks for the tip. I guess it stands to reason as alcohol will dry out and take the natural lubricants out of rubber but I never thought it would do so to the point of fixing a swelled up hopup rubber. Time to go down to the dollor store and buy a bottle as my used glocks all have swelled hopup's from people useing too much silicon oil.

Thanks again for the tip :cheers:

yes, isopropyl alcohol will break down oil, but it also breaks down products based on petroleum by-products... such as some plastics & rubbers.
Put some in a film canister, put the lid on and hold it upside down. It takes less than a couple hours to soften the seal enough to spill out. Imagine what it would do to a softer rubber compound.

Note, I've never tried isopropyl alcohol on glock rubbers before, so I can't honestly say this is bad for your rubber hop up. I'm basing this information on past knowledge of alcohol storage.

It's possible that the KSC hop up rubbers are inert to isopropyl alcohol. It's also possible that it can break down the oils in the hop up faster than it can break down the hop up, in which case, soak it just long enough to get the oil out. Anyone care to potentially sacrifice a hop up rubber and find out?

I had to do it to my USP about 2 years ago for the same problem. Overlube.

It has also worked for me with AEG hop-ups as well, but those don't tend to get the same amount of oil on them as the GBBs do.

It should be noted that I didn't need to soak the rubber overnight or anything. 10 minutes or so seemed to do the trick.

most excellent. I'll be doing mine this weekend (glock hopup) and i'll post my results. From the sounds of it this is the perfect solution.

And of equal note, if you have a rubber peice of anything that is all dried out and cracked etc, you can use a product from MG Chemicals called Rubber Renew. It works great for things like printer rollors etc, however I have sucessfully used it on things like windsheild wipers, the rubber part of a car door that goes aginst the window, and even the rubber boot on my joystick. Any electronics store will have it as it's common used on rollors for electronics but i suspect it can have good application for airsoft use such as mag seals and o-rings etc. Just remember this is a wipe on/wipe off application as if you leave it on too long it'll eat away at whatever it's used on. Works great for taking off sticky residue left from price tags etc... bascially it's an acid and you should use it as such.

Material compatibility tables generally list silicone rubber as being compatible with isopropyl alcohol. I'm not sure exactly what composition KSC uses, but I'd guess it's a typical rubber which the material table I looked at applies to.

Why is it that KSC hop ups absorb silicon oil so easily? I've ruined one in the past as well.

my guess is it's just more pourous then other rubber such as that which is used for o-rings etc. But even then o-rings sweel with enough silicon oil and time. I'm sure Carl has a much more technical explaination ... take it away Carl ......

drumroll...

It's a bit counterintuitive, but silicone rubbers are actually not compatible with silicone oil.

http://www.efunda.com/designstandard...=Silicone#chem

Drives me crazy how the airsoft market is so fixated on silicone oil and silicone rubbers when they're not compatible. There are not many lubricants that are ideally suited for silicone rubber. The only reason I supply silicone oil is that it's safe for most plastics and the more mechanically important parts like nitrile/EPDM/vinyl elastomers. I have yet to find a lubricant which are good for silicone rubber and ok for the rest of a GBB. Airsoft manufacturers need to ditch silicone rubber and use urethane which is more tear resistant and compatible with a lot of similar lubes as more mechanically important GBB parts.