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Old July 3rd, 2013, 19:45   #61
ThunderCactus
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Remember, increasing pressure doesn't JUST increase pressure, it also inherently increases the amount of air being used, which translates to a higher uncompressed volume.

So since you're in the testing mood lol
What happens if you keep it at 115PSI with the long barrel and decrease the DP?

Just like a GBBR, the longer barrel allows more acceleration time for the BB, but that's because there's more volume being released behind it than is required. My point here is that you may be using the right pressure, but too much volume on the shorter barrel. Wasting gas.

So like in an AEG where you're working with a fixed volume and fixed pressure, if you move to a longer barrel you don't increase pressure, just the volume (by changing cylinder ports), and you gain some fps just by having longer acceleration times. You should be able to maintain the same pressure and just increase the air volume to maintain the same fps from short to long barrel.

So I guess tune the short barrel to 1.3J, and lower your DP until you get the fps difference between both barrels to around 30fps, and that should get you close to the minimum volume requirement for the short barrel. Assuming the DP can even close that fast...
You're not relying on springs, air temperature, blowback weights, blowback spring strength, chamber temperature and bypass valves to regulate the amount of gas you're using like a GBBR, you're able to control the air pressure and air volume just like an AEG, so you should be able to get it to mimic the performance profile of an AEG. At least when it comes to swapping barrels.

I'm certainly not saying you're tuning it wrong, just that it's not optimized to use the minimum amount of air

EDIT; our local guy's using .28g BBBs, 45PSI & 12DP on a 455mm 6.03 prometheus and that's real close to 1.6J (420 on .20s) AND doing 1500rpm But that's on a silver nozzle.
Sooooooo you might wanna switch to silver? lol
The smaller nozzle just chokes the air volume getting into the barrel, which actually makes it less efficient. As I understand it, the smaller nozzle allows you to get ridiculous ROF, buuuuuuut 45PSI and 1500rpm is a pretty strong argument for the silver nozzle...

Last edited by ThunderCactus; July 3rd, 2013 at 20:12..
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Old July 3rd, 2013, 20:19   #62
Cobrajr122
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This is all stuff I have played with before.

There are some pretty good discussions about it on the US forums with replicated findings, but its always good to experiment on your own too :P

The quick reference is usually pretty close, and a good spot to start fine tuning it. Changing the DP does not make a very big difference in FPS (as seen in my pics, an increase to the DP by 13 only raised FPS by 8).
So it cant be making too much of a difference with the amount of air being used, I think.
I'm sure you could save a small amount of air by minimizing your DP, but sometimes you need a higher DP to achieve a better BB trajectory. A loss of a small amount of shots is totally worth more range and accuracy to me.

-----

Fine tuning the DP is a bit of a long process. Finding the right setting gives the BB a stable trajectory and max range at that FPS.

First you choose a a muzzle energy that you want to game with, say 1.38J or 385FPS w/ 0.2g

Using the quick reference for a 300mm TBB @ 1.38J I get a DP of 18

-Set up the FCU then tune the PSI to get 1.38J with the weight of BB you are going to game.
-Get a nice long range to shoot, shoot and watch the BB path.

This is where you just play with the DP, up or down, then re tune PSI (should not change much, if at all)
Shoot again and see if the BBs path has improved or not, play around with the DP some more until you get the best trajectory.

I have seen guys post up in the US that they will get a great trajectory at X DP then as they move it up its gets worse for 5~8 DP then starts to get better over the next 5~8 DP and eventually very very good again. So there are obviously different settings that achieve the same result, so you can find the lowest one possible to save on a little bit of air.
-I have not seen this effect with my rifle though.



EDIT

Quote:
Originally Posted by ThunderCactus View Post

EDIT; our local guy's using .28g BBBs, 45PSI & 12DP on a 455mm 6.03 prometheus and that's real close to 1.6J (420 on .20s) AND doing 1500rpm But that's on a silver nozzle.
Sooooooo you might wanna switch to silver? lol
The smaller nozzle just chokes the air volume getting into the barrel, which actually makes it less efficient. As I understand it, the smaller nozzle allows you to get ridiculous ROF, buuuuuuut 45PSI and 1500rpm is a pretty strong argument for the silver nozzle...

Yes, I have have said before, the 'wide boar' nozzles allow you to run a much more efficient setup. There are also 2 flavors of wider boar poppet valves (gold and red) you can get that will also be much less restrictive. I have not really paid too much attention to these so I can't comment much on them.
I also usually try to stick between 1500 and 1800 RPM. Give me a very nice and crisp 3 round burst :P

If he ever moves up to 0.3g+ BBs he will probably need to increase his DP. I plan on testing out 0.30 to 0.36g BBs to see what works best for me. P* systems seem to thrive on heavy BBs so I want to try it out.

Last edited by Cobrajr122; July 3rd, 2013 at 20:45..
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Old July 3rd, 2013, 20:46   #63
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I think you're missing my point
The DP directly controls air volume
So if you're already OVER the required volume for that barrel, then it raising it won't make any difference since it's just pushing all that extra volume out of the barrel after the BB has already left.
Given my local guys results with the silver nozzle, I'd highly recommend getting one, because polarstar's fps chart makes no sense to me what so ever.

Taken right from their site:
Quote:
Results with a .20g BB using a 6.05mm barrel at 120psi
Blue
CQB (275mm) = 380fps, Carbine (380mm) = 405fps, Rifle (509mm) = 435fps
Firstly, who the hell uses .20s? lol
They're at 120PSI, using .20s. I'd bet if they threw .28s into that same setup, their muzzle energy would be WAY higher than what they're getting with .20s
I'm guessing they're recommended nozzle based on highest ROF performance

The guideline states the silver nozzle is close to 2.3J at 120PSI, but at 45PSI you can get 1.6J from a .28g BB
With a smaller nozzle you NEED to run significantly higher pressure since the air can't get out of that tiny hole fast enough. Larger hole, less pressure, less performance strain on the valves, more effective use of the air volume that's being used, more efficiency.

It's important to note, there isn't 115PSI of force behind the BB while it's moving through the barrel.
If you're at 1.6J at 115PSI with a blue nozzle, and buddy is at 1.6J at 45PSI with a silver nozzle, there is exactly the same pressure behind the BB while it's in the barrel.
The difference is your blue nozzle requires more pressure to get the same amount of air volume through that tiny nozzle in the same amount of time it takes to get the same air volume out from a larger diameter hole.

I know nothing of the actual math to figure out pressure and air volume calculations through different sized orifices, but using less pressure to do the same job is typically more efficient. The main reason for using higher pressure is to achieve higher torque value, which you really don't need a lot to push a .28g BB lol
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Old July 3rd, 2013, 21:16   #64
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I completely get what you are saying, I am just repeating what I have learned from other users in the south where the system has a much larger user base that has gone though a lot of the math and experimentation to find what works.

I think where I am getting the idea of running a higher DP then needed is because of the ORGA wide boars. (In fact, I'm sure that was the topic of discussion that I have been remembering) Since the point of the Orga is to create a cushion of air around the BB as it travels, a higher volume of air would definitely be needed since a chunk of it is passing the BB. If you were to tune it for the exact volume of the barrel, air would pass the BB and then there would be no pressure left to keep accelerating the BB before it leaves the barrel.

For a TBB none of that would be required.

When P* released the system, I think they intended people to always run around 120 PSI, so they brought out the different nozzles to regulate FPS at the PSI. It was the user base that said no, we want to run different PSIs and discovered that the less restriction to airflow there is, the more efficient the system is. It was the user base, not P*, that came up with the idea for higher flow poppet valves to further make the system more efficient. There are even Red + nozzles out there.

They probably used 0.2g BBs because that is what everyone uses as a benchmark for chroney.

One thing I am not 100% on is the heavier BBs picking up energy like GBBRs do.
FROM MY UNDERSTANDING, I could be wrong - Propane and C02 expand much more rapidly compared to HPA once release into the barrel.
I am sure heavier BBs still pick up more energy, but I don't think it is even close to the same scale as propane/C02
^^Another thing to play with :P

One thing you need to remember about P* when they first started - they were never an airsoft company, they made car parts! lol
One of the employees was probably an airsofter who started to make some parts for bolt actions years ago, then managed to win over their bosses with a pitch for the FE :P

I have a red nozzle that I usually use, I just threw in the blue for that demonstration because I knew the PSI differences were going to be greater to better illustrate the point being made.
I want to try the higher flow poppet valves as well, but I would like to see how low of a PSI I can achieve first with the TBB 509mm setup. If its about the low to mid 40s then I wont bother with the high flow poppets, because I dont think the P* will run very well below 40 PSI lol.

^ Many edits up there ^

Last edited by Cobrajr122; July 3rd, 2013 at 21:24..
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Old July 3rd, 2013, 22:50   #65
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If I saw your edit before I posted, I don't think I would have posted at all LOL

Although it's not using propane, air is still a pressurized gas that decompresses the same way, it's just less affected by external conditions obviously. Because you control what pressure and air volume is used, you can make it have the FPS profile of a GBBR or of an AEG.
The reason GBBRs have high muzzle energy with heavier rounds is because they're using more gas volume than is required for the cylinder. They can't use more pressure since they're limited by the max pressure of what's in the mag. Of course, higher temp = higher pressure.
The BB takes longer to accelerate and is therefore in the barrel longer, and so as long as the poppet valve or gas valve is open, the same pressure is constantly being applied to the BB, and therefore constantly accelerating.
So like an AEG, if you had the exact air volume you needed to get a .20g BB out of the barrel at 1.6J, you wouldn't get very noticeably more muzzle energy from a .30g BB because the piston stops generating pressure before the BB has left the barrel, and what's applied is just whatever pressure is left as the air continues to decompress.

Sorry if it seems like I'm explaining it too simply, I just want everyone reading this to understand!
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Old July 3rd, 2013, 23:07   #66
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Quote:
Originally Posted by ThunderCactus View Post
Sorry if it seems like I'm explaining it too simply, I just want everyone reading this to understand!
Don't worry :P

I understood that already.

I actually explained this to somebody else 2 days ago almost word for word of what you just posted.

--
My understanding of the difference between HPA and Propane/C02 is that when the propane/C02 is compressed, it takes a liquid form. This is why you hold a propane bottle upside down when filling mags, so the liquid gets in. Then the mag acts as an expansion chamber, allowing some of the liquid to expand into gas that is ready to be released into the barrel.

When this gas releases into the barrel, it still has a lot of expanding to do. This need to expand combined with the force it is being pushed into the barrel at are what make heavier, slower, BBs pick up more energy than lighter ones that just fly out instantly.

HPA does not compress into a liquid, and we only use it as a pressure source to propel the BB, no expanding of the air, or at least not nearly as much expansion as propane/C02.
--

Now with that being said...
I just tuned the 509mm barrel for 1.3J on BBB 0.2g then put BBB 0.28 in and got an increase of 0.15J, up to 1.55J.
So apparently I was incorrect about HPA not expanding as much. It expands plenty :P





I am going to do some research and find out if there is math out there that I can comprehend that will tell me the volume of air leaving the FE @ X PSI w/Y nozzle diameter and Z Time period (DP)

Volume of a cylinder is the easy part lol.

Hopefully this will help find the perfect DP, and have the math to back it up.
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Old July 3rd, 2013, 23:41   #67
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Well the reason propane and CO2 go to a liquid state, is because 1) they're liquid at 580kg/m and 770kg/m respectively, whereas an air/nitrogen mix is liquid at 870kg/m
But just because they're liquid, doesn't mean they're under tremendous pressure. There's only like 250-300psi in a coleman tank, and up to 4500psi in an HPA tank.
Whether it's liquid or not makes no difference, it's still a significantly higher pressure than the 14.7ish psi atmosphere, so no matter what the gas will expand when released

The expansion ratio of propane is 1:270, 1:500 or so for CO2, can't find it for air exactly, but oxygen is 1:860 and nitrogen 1:700.
Not sure what the vapor pressures are exactly (which is the real number we need to worry about), but through some google skimming I think HPA actually has a higher vapor pressure than CO2.... Someone correct me if I'm wrong...

Anyway, the same principles apply, they're all expanding gases, as long as they supply at least the pressure generated by an AEG piston (which is really low), they'll be able to accelerate heavy rounds faster than lighter rounds out the barrel, provided they have the gas volume to apply constant pressure behind it.

Last edited by ThunderCactus; July 3rd, 2013 at 23:44..
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Old July 3rd, 2013, 23:52   #68
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I bought acouple of nozzles to to switch between indoor etc but that was a waste. I took a green nozzle and bored it out Red+ nozzle to achieve my low psi setup high efficiency setup. I have been reading that sub 50psi settings run into cycling/feeding issue's. The airline not fully sealing when you first turn on the air which I have experienced that goes away after a few shots. I have been experimenting with my DP and I have found 12 works for me. DP tuning has help me alot on tighter full auto groupings. Do any of you guys got the P* app on Iphone? Its pretty niffy to get you base settings from barrel length and target RPS settings and then you fine tune from there.
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Old July 4th, 2013, 00:01   #69
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I was actually just playing around with 45 PSI after TC said his buddy runs it, It would not feed until I got it back up to a hair under 60PSI. I went back to ~45 PSI and cranked up my DN to get enough air in there to overcome the nozzle return spring so BBs could feed.

I have the P* App, it is a great reference tool for getting a good base program in before fine tuning.
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Old July 10th, 2013, 06:24   #70
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I'm currently running the silver nozzle with a 455mm prommy 6.03. Dp set at 12. I run it on 45 psi . Ner had an issue with miss feeds or any like malfunctions. Groupings with 3 Rnd burst at 100 feet are 3in. I'm pushing the full auto limit of 1.64joules. TC has on order a orga 6.13 barrel for me and I'm.excited to test it out. I expect pure sex from this combination. I'll share the results as soon as I have them.
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Old July 10th, 2013, 10:30   #71
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Heh, Japanese shipping, very efficient. Barrels are at the post office, I'll grab them on my way home!
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Old July 10th, 2013, 14:54   #72
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Just started reading this thread but i had a few questions:

If it matters i'm running it as a dmr (RS SVD custom fit the fe to a cutdown rs gearbox) with a 650mm 6.03 prommy in front of it.


-redline rig is it the best rig(most consistent)

-any other good faqs/guides i should read beside p* manual?

-aiming for 420 fps with .2s and useing .30/.32 bios

Thanks!
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Old July 10th, 2013, 15:28   #73
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Quote:
Originally Posted by Ditch View Post
TC has on order a orga 6.13 barrel for me and I'm.excited to test it out. I expect pure sex from this combination. I'll share the results as soon as I have them.
Let us know!

I'v got an HS5 installed R-hopped 6.23 300mm on the way. I am hoping for awesomeness too :P
It was suggested to me that I got for the 6.23 over the 6.13 because people are getting better results with it. Apparently the 6.13 was brought out to try and work with the fixed volume AEGs better. I am going to try and get a 6.13 as well with an HS5 installed R-Hop so I can compare them myself though.

Quote:
Originally Posted by Off_kilter View Post

-redline rig is it the best rig(most consistent)

-any other good faqs/guides i should read beside p* manual?

-aiming for 420 fps with .2s and useing .30/.32 bios

Thanks!
Everybody is saying that redline is the way to go, grab it straight from redline with their wideboar flex line.

There is TONS more info on www.pstartalk.com/forum.php and other US websites.

Dont aim for an FPS, aim for a muzzle energy, 1.63J in this case. If you chrono for 420 on 0.2 then toss in a heavier weight you will be shooting very hot.

Edit;

After the transaction I just had with redline today, I can do nothing but highly recommend them. Extremely quick to answer emails and and Jim withheld putting stock up on the site until he had contacted me first because I asked about an about out of stock item a few days ago. That is freaking service right there.

Last edited by Cobrajr122; July 10th, 2013 at 23:06..
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Old July 15th, 2013, 21:40   #74
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Here is Zeus fellas.

The first of 2 new m249 Polarstar units to the team (thanks Snoopy)

Was a pretty easy install once I figured out how everything came out. We have not fired it yet as I had to go to work. Will be testing it out tomorrow.







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Old July 15th, 2013, 22:26   #75
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I have a silly question
Why didn't you just use a G&P 249 that uses a conventional V2 mechbox?
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