AirsoftHawaii90 Posted October 30, 2008 Author Report Share Posted October 30, 2008 Wow, 20min Eidting only?.. I cant edit my post already.. Anyway, I went outside to test some of your guys suggestions before I took the gun appart again.. Turns out you guys my be on to something, After looking very closly at the Hop-up unit, It is indeed about 1 mm farther forward than it should! While shooting, I also got many odd groupings.. The assembled gun shoots around 280FPS, But when I was shooting slightly sideways at a Coconut (weird target I know) and it was penetrating much farther into the poor coconut.. Then the consistancy went back to 280.. I rember from my first testing of the gun, that the coconut I was shooting went into it, and didnt bounce off.. When it did penetrate, It was doing about the same volocity on about a 7 shot burst of Auto. This is definitve, and I will have to check all of my recent guns, aswell as a TM System I am workin on aswell! Maybe try the Oring suggestion at the camber.. Edit Yep, Just checked.. I am really glad I did.. It figures a Wire from the trigger was smashed between the Body and front unit, resulting in the gearbox being pushed up and back.. the Gap was the result of the 100FPS loss.. Jeeze, I didnt know it would be so much.. Anyway, Its shooting through the bottom of a can easy now. I am very pleased with the results, but Just for measures I am going ot go inside againand see what I can do about the piston compression.. Its fine now, But I think it could be better. More updates to come It stumps me still, How could the Hop-up unit move so far forward like that?.. The gun is assembled correctly aswell.. I will have to check again, but maybe the Gearbox is moved back slightly? Maybe the Wire?? Link to post Share on other sites
ertgunner Posted October 30, 2008 Report Share Posted October 30, 2008 the spring in front of the hop up can be missing Link to post Share on other sites
DanHS Posted October 30, 2008 Report Share Posted October 30, 2008 Yea, I doubt everything he rebuilt has a cracked cyl head, but it could be something he is doing is causing them to break, a lube that degrades the plastic maybe? I have seen piston heads with large ports not seal well though, I could never get my CA piston head to seal quite as well as any aftermarket one, it seemed that the air could seep around the o-ring somehow, as if the air pressure coming through the ports pushed the o-ring back but not necessarily out against the wall of the cylinder. In the function of the gun however it seems nominal, as a switch to a different piston head in my CA only got me maybe 5fps. I still think that big piston ports and an o-ring that's too small or imperfect would cause one to lose some power, but not that much, unless the o-ring was deforming as it ran along the cylinder so quickly, causing it to unseal. Good to hear that the wire was at fault in that case, I would think that the hop-up was being pressed forward by the wire. What about the other guns? Link to post Share on other sites
AirsoftHawaii90 Posted October 30, 2008 Author Report Share Posted October 30, 2008 I am checking Invantory on my other guns, especially my other Ver2 guns.. If hop-up compression is the problem again, I will try to Oring thing you guys Suggested.. Anyway, Thanks All for the help.. This thread could be Very helpfull to anyone looking for a Compression issue.. If anyone has a Suggestion, Please post here even if the thread is old.. Information helps.. As for the AK, What happened was the 16guage wire I use has insulation that is a bit thicker than normal, and couses a bit more effort to bend (good thing, Its heavy built) and this coused a wire to come out of place. It was sandwitched slightly and tilded the gearbox UP and the hopup unit Forward.. Leading to a small gap the Nozzel couldnt reach. The gun still fired, but It still had compression loss.. Link to post Share on other sites
zentaurus Posted October 30, 2008 Report Share Posted October 30, 2008 figures. leakage around the bb feed channel and the hopup compartment is usually the culprit in a large sudden decrease in fps. same with inconsistent loss, IIRC. with your AKs, you should also check the alignment of the mek, nozzle, and hop up chamber. while AK receivers are tight enough, mek seating can change during assembly when you screw in the fire selector lever. same thing with the pistol grip cum motor cover but this one is easy to detect since the pistol grip itself will not seat properly. there will be an fps loss with your mek/nozzle tilting up/down. and the angle of tilt can change with selector lever manipulation. thus inconsistent readings. late for the party but hope that helps a bit. Link to post Share on other sites
Docv400 Posted October 30, 2008 Report Share Posted October 30, 2008 A misplaced hop unit will only be possible of course on AEGs where the unit is sprung against the gearbox, and so effectively 'free-floating'. A lot of hop units are secured with screws, or sandwiched firmly between the box and body/outer barrel/whatever, with no movement possible. Hop unit movement may explain low fps figures on some AEGs but you've only mentioned AKs, which have screw secured hops, unless the one(s) you have are different from TM, JG, DE and many others? Link to post Share on other sites
counterassasin Posted October 30, 2008 Report Share Posted October 30, 2008 When testing the compression in the cylinder as many has recommended here, you should remove the nozzle as well first. Try with the cylinder, cylinder head, and piston + piston head. I have found out that this is a good way to check if the piston head o-ring is leaking and so on... I also found out that my fps jumped with 40fps by installing the pro-win hop-up chamber for AK's. Maybe due to the fact that it screws on to the gearbox. Link to post Share on other sites
zentaurus Posted October 31, 2008 Report Share Posted October 31, 2008 you're right doc -- misplaced (or slightly wobbly) hop units only usually happen on M4s and AUG-type units where they butt against the mek or something else. not like the AK where they are screwed onto the rear sight block. but even in the AKs, where the screw holes are plastic, they can get loose. the main thing, of course, that can happen with AKs is the misalignment between the mek, the nozzle, and the chamber. the most often noticed effect of this is misfeeding but sometimes it can also lead to leaks. in my experience. thing is, and i'm getting a bit OC here, wobbliness (or a small and varying separation between the nozzle and the bucking lip) is quite hard to notice. it's something like the hairline crack in the piston head. which i too discounted in this case because AH90 reported it happening to several guns. even when the hop up chamber is tightly wedged between parts (like two halves of a receiver?), these too can become loose with enough assembly and disassembly cycles even when the receivers are alloy. or when the tinkerers are a bit careless. or in a hurry when in the field. LOLZ, mate Link to post Share on other sites
Docv400 Posted October 31, 2008 Report Share Posted October 31, 2008 When testing the compression in the cylinder as many has recommended here, you should remove the nozzle as well first. Try with the cylinder, cylinder head, and piston + piston head. I have found out that this is a good way to check if the piston head o-ring is leaking and so on... I'd say leave the cylinder head out of the equation initially as well, as a leak in that could be mistaken for a piston head leak. I usually hold the cylinder end-down on a piece of rubber (section cut from a bicycle inner-tube for example) on a flat surface, then push the piston down into it. You can do it on the palm of your hand as well, with a rubber or latex glove on. Link to post Share on other sites
AirsoftHawaii90 Posted October 31, 2008 Author Report Share Posted October 31, 2008 A misplaced hop unit will only be possible of course on AEGs where the unit is sprung against the gearbox, and so effectively 'free-floating'. Hop unit movement may explain low fps figures on some AEGs but you've only mentioned AKs, which have screw secured hops, unless the one(s) you have are different from TM, JG, DE and many others? The example (and AEG I was most consirned with At the Time) was a Full metal Vector AK. What had happen, Was the Gearbox and Front end set were being pushed out of place, leaving a 1mm gap between the Gearbox shell, and acctual hopup unit. I found this is because one of the Trigger wires had gotten stuck, yet I managed to pinch the wire and get the front set and main body together. Because the Hop-up unit is screwed into Metal, Its not likly to strip or come out of place Usuaually... In this case, the entire gearbox assembly was being tilted upwards, and couseing the Hop-up unit to tip up aswell. This made the gun shoot, but not cycle BBs right, and in turn the loss of FPS I had the problem with many guns, but not every single gun.. Just recently, I have had the problems, And I am guessing now its my judgment and process of assembling guns. I dont useually pay attention to the Hop-up chamber being alined right, as It never struck me. Now, I am going through all of my recent AEGs to check if theres any leakage. The guns I had problems with, was a Upgraded Galaxy Mp5k PDW, Mp5, 1 M4, and 3 AK verients. The Mp5 I found out, had a bit to much lube on the Oring, it was just a bit to thick. The Galaxy on the other hand, I think, may have had the Hop-up chamber problem aswell sence it uses a similar style unit! Well, I think I am going to be more carefull, and use Silicon with those Orings more oftin.. Especially sence I am currently repairing 2 G&G guns with about $700 invested into each of them.. All Epower customs. When testing the compression in the cylinder as many has recommended here, you should remove the nozzle as well first. Try with the cylinder, cylinder head, and piston + piston head. I have found out that this is a good way to check if the piston head o-ring is leaking and so on... Yes, Lol I test both just in case.. I also check to see if theres any compression loss by blowing into the Cylinder with the nozzel exstended. Link to post Share on other sites
Docv400 Posted October 31, 2008 Report Share Posted October 31, 2008 ...The Mp5 I found out, had a bit too much lube on the Oring, it was just a bit too thick... Grease, especially when there's too much of it, will find/work it's way into the hop and barrel, which will also drop your fps. Which is why I never use any . I polish the cylinder inner surface to a mirror shine and just give a light squirt of silicone spray into the cylinder, through the nozzle, after assembling the box. Then push the piston fully back a few times with a long thin rod (again through the nozzle) to distribute the lube throughout the cylinder. Then I just do the same after each day's use, squirting into the feed tube with the AEG held muzzle-up. Then just dry fire a couple of times in semi, quick wipe of the inner barrel with a cleaning rod and cloth (or a pull-through if you have one) and store upright. Works a treat. That's the reflection of the cloth it's standing on you can see inside it... Link to post Share on other sites
Optomis Posted November 2, 2008 Report Share Posted November 2, 2008 I would try applying a very light amount of grease to everything just incase you are over-greasing. Also try using a lighter and quickly rotating the piston head O-ring over the flame for about 2 seconds. It expands the O-ring slightly and leads to getting a bit better compression which could help. Also make sure that the air nozzle is correctly inserted in the guns and the hopup chamber is fully inserting into the air nozzle and no air is escaping from the chamber/nozzle. Link to post Share on other sites
zentaurus Posted November 3, 2008 Report Share Posted November 3, 2008 a bit OT but, would you care to share how you polish the cylinder, doc? buffing wheel? or a piece of cloth and jeweler's polish? Link to post Share on other sites
infected Posted November 3, 2008 Report Share Posted November 3, 2008 It won't give you a mirror finish, but some toothpaste and your finger will work wonders on it. Link to post Share on other sites
Docv400 Posted November 4, 2008 Report Share Posted November 4, 2008 I might do a little video sometime, but here's the text version... I polish cylinders using an air-powered drill (an electric one will do), a 1/4" (7mm) (or there-abouts) long series drill bit (you want it at least 6" (150mm) long so you're not working too close to the chuck) and some towelling-type cloth, cut into strips a little wider than the cylinder length, so approx 4" (90mm). I use a metal polish called 'Brasso', which is made for polishing brass (as the name implies), but any metal polishing liquid/cream/paste will do. Mount the drill horizontally in a vice (or workmate-type workbench, although you can hold the drill in your hand if you're confident with it), with the drill bit in the chuck. Then take a strip of the cloth and hold one end against the drill bit (on top, with the 'loose' end out to the left), making sure you overlap the end of the drill bit by at least 3/8" (10mm) to keep the tip covered, then wind the drill bit clockwise, by hand (the way it would rotate if you were drilling with it), rolling the cloth tight around it as you go. The idea is to get just enough cloth wound onto the drill bit so it can just be slid into the cylinder. Cut the cloth to length when you have enough wound round the drill bit. Smear some of the liquid or cream polish onto the cloth and then slide the cylinder over it (clean the cylinder first). Now hold the cylinder firmly and spin the drill. Work the cylinder back and forth by about an inch (25mm) for approx 20-30 seconds, then stop the drill. Take the cylinder off, remove the cloth (which will now be black at the end that had the polish on) and wind it onto the drill bit again but starting with the blackened end, so you end up with a clean outer section. Put the cylinder on again and spin it up, working it as before. Take it off and marvel at the shiny surface . If it was particularly grubby to begin with, you may have to do it again. If it's really dirty, it's a good idea to put a little cleaning solvent (carburettor cleaner is good) on the cloth for the first spin, then do one or two times with the polish. It sounds a little risky but if you're careful and sensible there's little to worry about. Once you're confident that you're not going to lose any skin/flesh/fingers, you can hold a piece of cloth on the outside (with some polish on it) and let the cylinder spin, polishing the outside in the same way. The usual H&S idiot-proof warnings apply here of course Link to post Share on other sites
-FIDO- Posted November 4, 2008 Report Share Posted November 4, 2008 i always grease my cylinder head to death..never had any problems but im using good lube..and yes youre right my barrel is alwas full with excess grease some cleaning and everything that isnt needed has gone... Link to post Share on other sites
zentaurus Posted November 12, 2008 Report Share Posted November 12, 2008 office net and my home DSL on the blink lately so have not been visiting. thanks, doc -- knew you had some other way of doing it as i could never get a mirror finish. @ infected: yup, have thought of using toothpaste after trying out jeweler's rouge and glass grinding compound. Link to post Share on other sites
-FIDO- Posted November 13, 2008 Report Share Posted November 13, 2008 dont get this polishing stuff...how long will it take for the brass to oxydize again? (even with grease) Link to post Share on other sites
Docv400 Posted November 13, 2008 Report Share Posted November 13, 2008 Like I said, I don't use grease, I use silicone spray. Sprayed into the cylinder through the feed tube after every use, it should keep it in good condition until the next strip-down. Link to post Share on other sites
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