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Old 10-30-2011, 06:17 PM   #1 (permalink)
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Will a PGP run on HPA?

I seem to remember reading or someone telling me that trying to get a PGP to run on HPA is a bad idea. However, if I was to get a constant air adapter and shove that sucker up into the PGP and run HPA through it, would it work? Or would I burst the seals on the valve or something worse?

It seems like it would work as it wouldn't require a certain pressure to cycle the bolt since it's pump. Anyone know the answer? Anyone try running HPA through a PGP before?
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Old 10-30-2011, 08:12 PM   #2 (permalink)
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My P68AT dislikes compressed air. Velocity around 220 with a good paint to bore match. Switch to CO2, I was fine. My PPS superstocker worked fine on compressed air. Unsure of how different the valves are.
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Old 10-30-2011, 08:30 PM   #3 (permalink)
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Sheridans do not perform well with HPA(Hindering Pressure Air) I could not get above 227 fps using a LB or P68AT. They both had a RVA & valve work done.
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Old 11-03-2011, 12:14 PM   #4 (permalink)
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With HPA you you will need larger airfrow than has stock PGP - HPA is not so "nutritional" or "powerfull" for the same space of gas, like (heavier and dense) CO2 and the crossections in the valve are also to small for HPA.

Surely it can help a little when you use weaker valve spring than is the stock and you can even a preload the stock hammer spring for ~1/3 more strenght on the hammer (then, with a lot larger valve dwell you can push more gas trought the small valve crossections... it is inefficient, but trought it is likewise a way, how entlarge the muzzle velocity). Perhaps it will be sufficient...

With performance tunned Sheridan you should have no problem - entlargement of the passages where goes the gas = boosting the airflow is the basic part here, also such like markers have commonly improved the gas flow good enought to use HPA (velocity adjustment will be necessary anyway, like in any other marker - HPA and CO2 are simply different).

By the way, with standart, stock PGP, it is big problem go with the muzzle velocity above ~265 fps even with CO2. The marker was created with simple modification from existing BB gun (something like Sheridan EB17/20) what was shooting smaller and lighter pellets a lot with smaller kinetic energy than has the paintball marker (~7,5 Joule - pantballs around 300 fps have around 13 Joule KE), so the stock PGP with the same valving is inefficient for larger velicities/kinetic energies. The optimal velocity for the stock valve is imho around 235 fps with CO2. With boosting of the airflow and (reduction of the valve dwell) you can push this border to 250 fps or even more.

Last edited by 3022; 11-03-2011 at 12:20 PM.
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Old 11-08-2011, 08:46 PM   #5 (permalink)
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3022, your answer actually makes sense why you'd get lower performance out of HPA.

I've got an RVA on my PGP and actually have it set around 235 fps with CO2 as I also found it to be a pretty good velocity to keep it at. With such a short barrel, any higher tended to make the balls too inaccurate for my liking.

Perhaps the longer barrels on the P68 and LB slowed the balls down too much for HPA to be viable? In any case, at least I know it will "work" without destroying the insides of my PGP.

Thanks for the help guys!
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Old 11-09-2011, 11:07 AM   #6 (permalink)
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I think that bassically it is not necessary to say more... and especially afflict more pain to readers what have english like first language with my horrible english... but I feel some personal necessity to say more to this theme:

Imho:

Longer barrels commonly do not slow the ball when is the chamber good sealed - the force of the presured gas what accelerates the ball is commonly a lot bigger than friction what slows him.

There are surely conditions and variables what play the role (especially how is the paint sealed in barrel, how is barell and bolt sealed, what are the valve characteristics, what for porting and finish has the barrel...) but in major cases, longer barrel = more efficient barrel.

Sure, when you will have big muzzle velocity, efficiency, and accuracy, long barrel is not the most essential - paintball markers are not sniper rifles, or cannons... but longer barrel will hurt the efficiency only in very few cases.

I think that the well-know statement from Tom Katye from AGD about the efficient barrel lenght was misunderstand from major part of paintballers, and because that his effect was more deleterious rather than helpful for the paintball comunity. It is so because the readers commonly do not realize that this Tom Katye statement was based on experiments on Mags and the Mags have not sealed the barrel around bolt; what means that the gas will here leave the barrel faster (or precisely the pressure decreases here faster), in shorter time, than will be the ball meet the longer lenght of barrel.
...similar it is on cheap blow-back semi-autos - the bolts are here not good sealed and the bolt opens itself during shoot with blow-back... and the barrel ID is here often too bit, the ball do not seals in the barrel properly.

But when goes about most of pump/stock-guns, the conditions are sightly different here - the bolt is here commonly closed and very good sealed. Tight and longer barells are here commonly more efficient than shorter, trought that the efficiency gain is not linear here, and that its addition decreases here quadraticaly (i.e. 16" barrel has surely not 2x efficiency of 8" barrel)... but the efficiency/velocity rises here at least until 20" of lenght.

With my P68SCs I was always able to get bigger efficiency and bigger muzzle velocity than with my PGPs.
With my CA pumps with interchangeable barrels, I have always bigger efficiency and bigger muzzle velocity with longer barrels with the same ID.

Surely, it depends on many variables. One of Glen Palmer statements was that in the paintball marker, the valve needs be tunned properly to the barrel and second statement was that the efficient marker is accurate marker, the efficiency is here commonly conected in some way with accuracy (or better with consistency). Imho are these statements not exact, they are to much simplified for that, but they are good enought to be usable.

We can say, that with shorter barrel, you need have bigger airflow and shorter dwell, to get the same velocity like with the longer barrel.

But with my tunned ZGP-94 (bassically the same marker like old style PGP), with some experimental settings I was able to get 450+ fps without negative effects on accuracy or consistency (efficiency will be not larger, at most the same in the ideal case - you simply pay for the kinetic energy what you will get) - it is more question of the valve (and his elements like hammer and springs) than the barrel. Valve is really heart of the marker. You need have good barrel, with decent lenght and proper internal diameter, but match the valve to the barrel and you will be able to get best from your marker.

Velocities above 300 are naturally not usable for paintball, even 290 fps is here to big when you consider about short-range encouters and velocity spikes/velocity inconsistency in real conditions, but it is really possible to convert the regular PGP in condition that it will be most efficient/accurate in velocities around 250 or 280 fps. The barrel lenght is not the problem. 6" are good enought.

There are for example some of my old chrono results from one of my PGP and P68SC (velocity/shoots no.):



and comparsion of the tunned PGP with the stock PGP:
http://www.pgp.mysteria.cz/ladeni_P6..._PGP_685Ti.gif
average muzzle velocity of the tunned PGP is here around 250 fps and it was one of the most accurate marker what I have own.
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