HATSAN 135 has a larger Swept Volume than the 125 - HATSAN Data !

[rsterne]

I now use 100psi to estimate the best barrel length for maximum power in a .177 spring gun.

An interesting idea.... That works out to about 2.5 lbs. of resistance on the pellet.... Probably usuable in other types of guns and calibers (with adjustments)....

Bob

[Scotchmo]

...
What are your thoughts about Piston Weight with a Gas Ram change to a 177 - 180 bar Gas Ram ?       Heavier ?        Lighter ?

Is this the piston you are referring to ?

http://www.n-forcer.com/content/pdf/Mini.pdf

I assume you are talking about the MF25-125 BL ( 225 lb initial / 305 lb final ) with 1280 psi pressure.

It is interesting to see the higher force available, at a lower pressure, due to the larger diameter components.

I am concerned about cocking force and strain on the internal components of the rifle, especially the Sear and other Quattro trigger components.

Thanks !

Dave

Piston weight -
That depends on a lot of factors which I have not been able to quantify. Chamber volume, piston diameter, spring energy, pellet weight, caliber, pellet friction and maybe more. It is a tricky balance to get the optimum piston weight. The gas spring force by itself can only generate maybe 200-300psi in the chamber. So we rely on the inertia of the piston to get the high pressure spike to propel the pellet. Ideally, the piston will not slam hard. It will come to a soft landing at the bottom of the chamber. The pellet will have moved down the barrel by enough to drop the pressure to the point where the spring force can resist the rebound pressure. That way the piston will not bounce back off the air column. I believe that the hysteresis in the gas spring is an advantage to help minimize piston bounce. Versus a wire spring, a gas spring should have a greater tolerance in acceptable piston mass. The best advice I have is to make the proper spacers from a dimensional standpoint and test it. You can adjust the weight from there but you will probably be close enough already. Optimum is difficult to achieve. Close enough is fairly easy to achieve with a gas spring.

The MF25-125 BL. Yes. That would be the next step up from the MF19-125 YW.

You should be concerned about the cocking force and stress on the trigger components. That is why I like to stick with a gas spring that has a maximum force about the same as the maximum force of the wire spring. Since the gas spring has a higher average force than a wire spring, you can still get a performance boost. For a given force, the gas spring will develop approximately 20% more ft-lb of stored energy. But remember that the limiting factor on FPE is the chamber volume, so that 20% increase in spring energy will not necessarily translates into 20% higher pellet FPE. Though in some tests with a rifle that had an underpowered spring, the increase that I got was actually greater than the increase in spring energy. If the wire spring is already overpowered, you may not see an increase in FPE.

[JJ1514]

Would the MF25-125 BL wear out parts prematurely and be harder to cock than the mf 19-125? Has anyone tried a MF25-125 BL in a Hatsan mod 135

[Tarheel]

I haven't heard anything about using the MF25 pistons rather than the MF19 model, online.

My main concern is safety, both when cocking and shooting a "hot-rodded" break-barrel. At this point in time, I think I would stick with the MF19-125 YW "Mini-Forcer" Gas Ram.

Dave

[JJ1514]

I will, thanks for the advice tarheel

[Smackey54]

Would the MF25-125 BL wear out parts prematurely and be harder to cock than the mf 19-125? Has anyone tried a MF25-125 BL in a Hatsan mod 135

The can diameter of the MF25 comes into play when considering the inside diameter of the piston of the Mod 135. A one-inch can would not fit inside the piston of the WFH, which it must do to allow the piston to travel far enough back to engage the upper sear. I am only speaking from experience with the WFH and do no know what the Mod 135 piston ID measures.

[JJ1514]

Thanks Smackey, I'm gonna stick with the mf 19-125 yw, don't wanna risk it

[Minero]

Tarheel,

It would be intresting to see the CCīs of the new Gamo Magnum as it has a 33mm piston, but donīt know the stroke.

[Bryan Heimann]

Minero, Welcome to the GTA. 

I think the Gamo Magnum is the same gun as the Hunter Extreme.

[Minero]

Bryan,

Intresting as the weight of the new Magnum is very light compared to the extreeme, although it has a new barrel with a faster barrel twist, that is what made me look at it, and went ahead to buy, once I tested will update, right now should be arriving to my cousin house in Tx, hope to have it by end of the month in my house but I will be home till mid september (working out of country).
The Extreeme has a 33mm piston?

Eager to test it, as well test my daughters striker and son NP2.

[longhunter]

Thanks mag man and dave i am having a really hard time trying to figure out what to get the 135 or the torpedo. and is the torpedo a good fit for nitro conversion, i dont know how the setup is on this underlever.

Unless you're built like an orangutan, get the 135. The 155 is really a workout.  You don't have the leverage, with the 155's under lever, that you do with the longer barrel of the 135. That and it's really a stretch to reach the end of the under lever. Especially sitting with the butt resting on a chair, between your legs. I'm 6', by the way.

[57West]

I realize this thread is back from the dead but I am interested to know how the conversation to the 180 bar gas ram went and what the results were?  Does anyone know?

[Bryan Heimann]

I think it resulted in a bent cocking arm.  Or was that the 200 bar ram?  I remember a little about it, there was definitely a point of diminished returns.  You can only get so much power out of a fixed volume of air, no matter how fast it is compressed.  Past that point, stronger rams just tear up your gun and reduce your accuracy.

[57West]

That makes plenty of sense.  Thanks, Bryan.  Im thrilled with the stock piston in my 135, but now that I started digging into my airguns I am growing more curious on what to experiment with.

[UnderPressure]

The large swept volume of the 135 makes it more suitable for larger calibers. On my experiments with rifles of smaller chamber volume, I decided that 100psi was the cutoff point where barrel friction overrides any FPE gain from the the remaining air pressure in the barrel. I verified it by doing a progressive chop of a .177 barrel from 18>15>12>11>9 inches. I now use 100psi to estimate the best barrel length for maximum power in a .177 spring gun. A Hatsan 135 in .177 caliber would need a barrel that was over 30 inches long before it used up all the available energy in the air. You can make the barrel shorter and it will work fine, but you are wasting some of that large chamber volume. For comparison, a .25 has 100psi remaining with a 15 inch barrel. Friction relative to bore area is not the same for a .177 and .25 so it may not be a direct comparison. But it is useful data. .25 is probably the best caliber for a rifle with the chamber volume of the Hatsan 135.

By that same math I reckon a .30 Hatsan 135 would only need 10.4" barrel length for 100 psi. (The quiet energy version of the 135 has 10.6" Barrel)

So hypothetically (ignoring barrel friction) a .30 cal 135 should have the highest muzzle energy of all the Hatsan 135 calibers (.177, .22, .25, .30) for the 10.6" barreled QE (Quiet energy) variant. However, I think the pellets we currently have in .30 are too heavy. Maybe some alloy .30 pellets or lightweight .30 lead pellets or slugs will show us a larger delta in muzzle energy than we currently see?