[kopzaxx4005]

Currently I own 2 snipers rifles which are upgrades m24 snowwolf and upgraded FN spr a5m. Both of them have been installed with R hop + 6.02 inner barrel (same length as stocks). Cylinders, 9mm spring-guid rod, sp150 spring (9mm diameter) and especially piston head.

Both of them have 100% airseal. After shooting, i plugged my finger at the end of barrel and it could hold air quiet impressively (i held only 10 secs but Im sure it could go longer).

I talked to sniper tunning mech I know. He suggested me to switch O-ring to the smaller one and I did so. Surprisingly, the FPS increase, better range, and more consistent shots.

I have read so much about airseal theory but seriously this is the result of what I got so far.

From what happened, I think 100% airseal doesnt always mean better performance. I only completely seal a nozzel, a hop-up unit and installing littler smaller O-ring on piston head. This will reduce friction from both cylinder and excess air pressure (which trapped inside cylinder). IMO only certain amount of air that will used to drive the BB and the excess will slowdown piston which also reduce air velocity to drive BB.

Since the only certain amount of air is used to drive BB, the excess should be let out to allow piston move faster => faster air (higher pressure behind BB), better fps.

I am not an expert. Im sorry in advance if I dont use proper or correct technical terms, as also the fact that english is not my native language.
Im just sniper lover who always take apart, tune, break it, fix it and experiment it. I dont know if you agree with me but it's worth a try. Lemme know what you think about it or if possible experiment it and share it.

Thank you

 

[Hamlet]

Have you chrono the two setup? I mean how was the improvement?

 

[Zero Roaster]

The secret to a really good sniper rifle is consistency. You would have to bled off exactly the same amount of air with every shot so your BB's would remain stable from shot to shot. The air would also have to bled off in a way much like the ported cylinder on an AEG works so that it doesn't interrupt the cylinder to hop up seal and again throw the BB off course.

As for bleeding any air, there is absolutely no advantage to doing that and if you need to reduce power, do it with a lighter spring or piston. The idea is to match your air supply to the demands of the rifle so that you don't have to bleed off any air. Hence, ported cylinders. Going back to consistency for a moment, if you have achieved the right balance between the air in the cylinder to the barrel, and matched with the correct BB, the shot to shot variance should be negligable. For example, in my L96, I have a variance of +/- 1fps at 474fps chrono'd with a .2g BB. So, that would mean that when I chrono the gun, the highest I get is 475 and the lowest is 473 regardless of how many shots I put throught it, provided of course the BB's are consistent. The seal is very tight and the system recreates the same shot time after time with little to no variance.

Air is elastic, always keep that in mind. That means that you must also account for temperature and barometric pressure when adjusting the gun. Is coming up with a bleed screw a good idea? It would be fantastic for velocity control...but ideally, instead of bleeding off air, you'd probably want to maintain the perfect air seal and just produce less of it to keep the system stable....like a ported cylinder.

In theory you could tap the cylinder head and install a jet to bleed it off, but again, no real advantage unless you just need to quickly drop your fps for some reason.

 

[kopzaxx4005]

Firstly thank for sharing your thought

Yes I have chronoed it and the fps increased from 510 to 520-525 (on air-leak experiament)

I always had been using the air-seal theory for entire of my bb sniper life without doubting it.
but then one day this guy just came up and told me to experiament the air-leak method(use little smaller o-ring on piston head). All the things that I believed in and read are crumbled.

On first attemp, I make sure everything was sealed 100% by using big o-ring on piston. assembled sniper and tried to shoot with plugging at the end of the inner barrel. No single air leak or at least a very very tiny amout of molecule (lol). now I make sure Hop-up uni and cylinder are not factors cuasing it. I chronoe and rage tested of course. It gives 507-512 fps. On range test, i used 0.36g bb, R-hop, novrtsh zero-in scope thats how I set my hop up.
I tested in my own rubber tree plantation. Range was pretty impressive (not really sure but at least 90 meters or more. i measure distance by trees lol)

second attemp I switched o-ring to little smaller one. the bolt action is much much smoother.
I tested it with 0.20 gram (always) the fps increased to 520-525 fps. The shots are little more consistent and range has improved a little.


I have zero idea of how exactly it works. but seriously it gives higher fps, consistency, range somehow.
I really want some of you (possible all sniper freak) try this out. its worth a try.



ps. my account is new but in fact i always come and read here. just never comment.

 

[kopzaxx4005]

https://www.airsoftsniperforum.com/...ir-seal-gaining-fps.html#/topics/47937?page=2

 

[kopzaxx4005]

On my FN SPR A5M (stock spring, R hop)

1st attemp: upgraded tight fit C-type piston rubber head (100% air seal) = 390fps

2nd attemp: same piston but just change rubber head to little bit smaller one (~50% airseal) = 430fps

 

[Fluppi]

Well I must say I am sceptic. To me it doesn't feel like the shots would be more consistent than they are with 100% airseal.
Could you shoot 5 bbs with each setup and show the fps result?

 

[kopzaxx4005]

Yes I have tested more than 10 shots each round. Sadly I was too overwhelmed sk i forgot to take photos.
the chrono is not mine and the owner already took it back. thats why i hope someone can do it not just for me but for all of us to confirm this.
It would also be less reliable if the result again comes from me. just anyone owns chroro and several size of O-ring or C-cup piston head, please spare little time to test it. Im also sceptic as most people in sniper comunity always suggest 100% for the best result.
As far as I haved tested, its more fps and consistent than 100% airseal. as you can see, I own several piston head. I spend extra money to get fit rubber c-cup piston head. TBH Im also little annoyed and quite sceptic about how can this is happening.

 

[necrosis01]

I believe you since i experienced similar things. When i had perfect air seal, piston and o-ring had to be a very tight fit in cylinder and the piston's speed loss was bigger than air volume gain compared to not perfect air seal but not so tight fitting. One important thing is consistency as said above but it doesn't equal to perfect air seal imo at least with such parts and materials some rifle uses. With no perfect air seal, consistency depends on how much air escapes out, so if that air is between a certain range it could be more consistent with perfect seal, because altough in that case you have no air escaping out, but friction effecting piston speed and that also effects consistency. And because o-ring is tighter it has more contact with the cylinder wall, so the slowing effect can maybe vary more compared to the amount of air escaping from a not perfectly sealed cylinder/piston. O-rings are rubber, and this has to features: first, they seal very good since they are elastic, they can fill the microscopic gaps on the surface (in this case, the cylinder wall inside), stopping the air to leak out. This is good for us. The other feature is that it has a high drag coefficent, so high slowing force occurs when moving on the surface. This is bad for us beacuse it's slow the piston down too much. The tighter you fit the piston o-ring, the more microscopic gaps getting filled by the rubber -> better seal but also higher slowing force. You can use some lubricant to decrease this effect but using too much is contraindicated as it sprays into the hop up unit and barrel, and it's also not good. The key is to find a balance between the two, where it gives the best fps and consistency. This may not be at the same point (so you might find the best fps and consisteny at different grade of sealing) and it may not be at the 100% airseal.
The best alternative instead of o-ring would be such a material, which gives very good seal, and low drag coefficent at the same time, like in an engine piston. It seals good (to have high compression) but moves easy, to give high rpm. Don't know if this is possible to do, but some day maybe someone makes one. It also requires highly precise cylinder and piston sizes, so i doubt this would be affordable to average airsoft players, but for an experiment, it would be very interisting. Also, if an internal lubricant system would be made which provides the right amount of oil or silicon to keep the piston moving easy, without getting in the barrel and hop up, would be very cool. But in such a small and (relatively) cheap system like airsoft sniper not designed to produce and handle high performances and effects like a combustion engine, these may be too complicated and expensive to do.

 

[kopzaxx4005]

thank you for sharjng your thought.
Your explanation could be new break-through in sniper rifle tunning community.
So basically we just need to balace between piston speed and amount of air sealed.

Smaller O-ring = piston can move faster which gives higher fps

IF too small O-ring = air can escape too freely can also cause inconsistency

Bigger O-ring = help with consistency

If too big O-ring = more friction can also cause inconsistency

Therefore, i guess we just need to find balance or perfect spot right in between.

Thanks again for your explanation

 

[Zero Roaster]

I agree, necrosis01. It only works if the loses are also consistent. In my personal experience, one hundred percent seal has always yielded the best results. Now, here's a couple of tricks. I use a viton o-ring instead of rubber. Less drag, less likely to deterioriate and will last for just about all of eternity in this application which equals consistency. Use a light synthetic lubricant. As light as possible...but also one with a high tack quality that won't wash out and keep the o-ring lubed.

Part of why an internal combustion piston ring works is that it's continually being lubricated under pressure with every cycle. Dry out those rings and it will die a quick and horrible death. hahahaha. Secondly, in the case of an AEG, the o-ring actually retracts on the back stroke and acts as a floating reed valve to allow air into the cylinder. It has to work the way it does...not so much in a bolt gun, but even in a semi auto AEG, you have to allow for that retraction to happen. That alone could be part of the consistency problem.

Ideally we could upgrade the materials in the airsoft rifle and get ridiculously consistent, but again, as mentioned, cost comes into play.

Lastly, it comes down to the ammo. I build my rifles with as tight a tolerance as possible, but what about the BB's? A BB of a certain weight only has so much ballistic potential, period. It's much like 'real world' engineering say like in a piece of machinery where the most cost effective level of operation would be 80% instead of 100% in order to achieve the most steady and consistent level of operation and compensate for the inconsistencies of material, etc.

 

[kopzaxx4005]

So basically either 100% airsela or airleak does not apply to everygun. Sometimes they are same brand and same edition but still require different tunning somehow. So we sbould not go all in 100% airseal. just try different airseal/airleak and see which seems fit best to each gun.
this is interesting. Ill buy my own chronograph and test some more but not anytime soon since i just spend too much on buying many different types of piston and o-ring.
So far, little airleak is perfect for me.

In the attachment, they are all pistons i got. From superfit, quite fit, slightlyfit, not fit at all.
There's bb field to play in my local area so most of the time I just test out ny snipers at different ranges and then tune them. All those pistons not gonna go waste. Im planning to buy more snuper to tune as test out as my collection (now got only 2). but for now just gotta buy my own chrono first so dont have to borrow every single time.

 

[kopzaxx4005]

edit: there's no BB field in my local area or even near by at all. Just my own rubber trees plantation (lonely life).

 

[1tonne]

Just a note to Kopzaxx.
You do not have an o-ring on the end of your piston. It is a suction cup or some people call it a plunger.
They can be a pain in the backside to get the right fit but once sorted are great. But overall, I prefer an o-ring piston head.
(Sorry I have not read the entire thread)

 

[kopzaxx4005]

I have both c-cup and O-ring
many sizes of c-cup
also many size of O-rings
and yes i have tested on all of them
ill post pic later now im just at work

 

[wyz2285]

Can confirm partly this.
With 0,2
When I use a larger o-ring that fits snug in the cylinder, 100% air seal, lower fps;
When using a o-ring that fits smooth in the cylinder, not 100% air seal but still pretty good, takes a few second for the air to escape, higher fps;
Both are equally consistent in practice.
With 0,4 the fps difference is reduced.

 

[Jeppe]

Is there any sound change from the piston when you change orings?

 

[wyz2285]

Not really, we're talking about a small difference of air seal. The smaller one even though not 100% air seal the piston still stops when you tap the end of the barrel, reaching the end after a few seconds after the air leaks out. The larger o-ring might be quieter but the difference is not enough to cause a impression.

 

[Plazmaburn]

I wrote a long winded post, took like 3 hours to write properly and the computer f'ed right off when I posted and it was lost. So to make a long post, short.

Many things effect airseal. Cylinder size, how well it was made, piston dimensions and design, the o-rings, material, size, the lube you use. The guide rings on the piston are doing their jobs. Temperature. Tolerance between parts.

Considering you have not listed any brand names at all is a bit odd and calls in some scrutiny about your results.

=====

On an unrelated note, you are in violation of forum rules by not having made a proper introduction post. Fix that, please.

 

[wyz2285]

Fine, will post pics when get home.
Piston is custom made, nylon head (made the o-ring slot wide enough to free float fit most of my suitable o-rings) carbon fiber body and steel sear, no guide rings, all parts made to 0,2 mm (or 0,3 need to check. End line is without o-rings the piston slides perfectly) tolerance. Airsoftpro chrome steel cylinder and cylinder head, PDI 520 FPS spring cut down, custom spring guide with bearings. larger o-ring is from an AEG cylinder head, which I know is a bit large for the cylinder ID, smaller on from a GBB mag which barely stuck in the cylinder. Can't remember the lube brand, some grey stuff for GBBs, I just put a tiny bit diluted with WD40.
Btw I did make a intro, nobody answered.
Already posted my gas ram project before.