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aircube · Veteran Member

In my quest to find a decent multishot co2 pistol I returned the Crosman airsoft C11 which kept jamming and bought a GAMO PT80 which is rated at 410fps and come with 3-8 shot circular clips. Reading through some reviews it sounds like the PT80 is a well built nice feeling fairly accurate and resonably powerful co2 pistol at a decent price.

I put in the first co2 cartridge and all of it leaked out, i could'e tighten it enough to stop it, so I tried another and it was ok. I tried four types of pellets, Crosman destroyers, RWS hobbys, Gamo round balls and skenco no lead.

The chrono results were horrible. I read on pyramid air that its rated at 410 fps and should shoot about 350fps. Well mine came nowhere near 410 OR 350. I was getting 230-260fps ! What a peice of DUNG!

RE accuracy; I tried shooting from 20' freehand and i was getting 2" groups and I was disapointed so i put the butt of the gun firmly on a table and shot a clip off and 7 out of 8 shots were within a nickel sized hole! not bad at all for a cheap pistol!

Conclusion: I really like the way this thing feels, it looks great all of the moving parts are very solid and work well, it feel like it will last and its pretyy accurate for a pistol. Perhaps there is somthing amuck with the pistol that I received, I can see how a MANF might rate an airgun a little high so that you are aware of the "maximum" speed the gun hit be capable of for saftey reasons. BUT come on, a gun rated at 410fps that averages 245fps thats garabage. This is my first GAMO, is this typical or did i get a bad one?

This FPS rating should be regulated, esp due to the fact that there are laws based on it. My crosmans say this gun will not exceed 500fps with standard pellets and it hits 480 tops. Whats the deal with GAMO?

AirGunEric · Site Admin

Gamo is all about the marketing and the numbers. That beings said, 250fps sounds low in any event. If you feel ambitious, and it being a Co2 gun, you could always smooth out the valve passages and perhaps drill out the valve plunger to improve flow. That being said, with it's short barrel, maybe around 450fps is all that can be expected from this platform.

Anyone ever improve a PT80 around here?

aircube · Veteran Member

Thanks Eric, I did acctually strip it down last night to check if something was amiss. Seemed the flow was quite poor through the nipple that pierces the co2 (maybe a peice of metal from the first cos cart? I clean out the nipple with a needle and tried to open things up a bit.

I checked out a diagram and it appears that there are two extra washer in mine in the valve?? That would make the valve return spring "more" powerful? What effect would that have? Would't that slow it down a bit by letting less air through? I don't have enough experience to know for sure.

I shot off a cart and there was a slight improvement, but I noticed that the co2 cart was really cold. The co2 was in the garage overnight and it went down to 10C 50 F and the CARTs are likely at that temp. So, i put a co2 cart in a pot of 35C 95F water for 1/2 hour and loade it up and I was shooting about 416fps with 7.9g and 460-490 with Raptors.

hmmmmm, so does that mean it has to be 35C 95F and sunny to get reasonable performance from this gun?

Is there a temperatur range, or ideal temp that the co2 cart run at?
Does this mean you have to recalibrate your site every time you shoot. 10 C one day and 30 C the next.

I did't realize this was such an issue with CO2, i guess I just bought a warm/sunny day gun. Laughing

AirGunEric · Site Admin

See the second table from the bottom: http://www.airgunhome.com/pages/calculators.html

aircube · Veteran Member

AH, so a 10C is putting out 655psi and a 35C is putting out 1165psi
(feel like a bit of a bonehead Embarassed

) i'm new to co2 guns. I guess I was getting some really decnet speed with the crosman airsoft C11 that i tried out.

I tried at room temp 21 C or 70 F and I got a solid string at 388 with 7.9g and a solid 390-416fps with raptors which isn't too shabby for a 410 gun. i'm guessing is rated at 21C with raptors. I like the 1165psi at 35C Razz

i guess i'll keep the carts in my pockets Smile

Now that I got the power worked out i'm feeling pretty happy with the PT80 Mr. Green

I dialed in the site and I getting pretty good groups, i'll post some pics in another post. Smile

aircube · Veteran Member

Well I hope my words are tasty, because I'm going to have to eat them Laughing

After eric helped me with the CO2 thing I dialed in the sites with the CART at room temp. I used 3 clips of 8 RWS hobby wadcutters at 7.0g .
The PT has a rear site that can slide right and left and can be fixed down with a hex set screw. I also found that if you overtighten the screw it will lift the rear site up a bit so you can compensate for vertical as well, this is quite limited though. I should mention that i also push ed the barrel back in its mount to get a tigher fit against the breech seal, because the crews were practically falling out from the factory and the barrel was sliding back and forth!

I shot the last 8 shot clip with her butt flat on a desk and held on tight with both hands while i shot (sounds like a office porno Laughing

) at a 3/8 bull from 20 feet.

The results were absolutley great! Mr. Green

and I have to say that this is now easily my most accurate gun at close range. Seems way more consistent than my springer rifles, although i am sure thats because of my springer hold technique, or lack thereof. Embarassed

So, heres some pics of the gun and the final 8 shots that could be covered by a nickel.

Sorry GAMO, I was very wrong, this thing is a definate KEEPER. Mr. Green

AirGunEric · Site Admin

Glad to gear you got it sorted out.

And yes, Co2 can be a pain in the a$$ when you don't live in a year-round warm climate.

aircube · Veteran Member

ya i guess theres pros and cons to everything. the seems the co2 is limted to >=21C or keeping the carts warm beforehand. But my the looks of the consistency of the velocity and the shots its def worth it. Smile

Alstone · Moderator & Site Supporter

I have a couple of Co2 pistols, the CP88 in standard form shoot between 300fps and 400fps depending on the weather, my other a Rohm target pistol which can be adjusted for tempreture change but only by a small amount.

What I do to better performance on a warn day is load the co2 capsul in the gun and leave it in the sun for 10 minutes this improves the power over a longer shot string. The thing is to get the gun warm as well, then as you use up Co2 and the capsul cools down some heat is transfered from the gun which keeps the power up, the more metal on the gun the better.

Al

aircube · Veteran Member

Thanks Alstone, great tips.

You mentioned that your Rohm has an adjustment for temp? WHat exactly does it "adjust"?

What components make a gas gun hold the valve open longer?

thanks

Alstone · Moderator & Site Supporter

broommaster2000 · Moderator

aircube · Veteran Member

Heres the valve diagram. In my pt80 there were (3) of part #W307, while in this image theres only (1) PN #W307

the part is a metal washer that sits between the O-ring (OR037) and the valve spring (cs684)

Does anyone know what effect putting more or less of these washers would be?

thanks

Alstone · Moderator & Site Supporter

More washers behind the spring closes the valve faster which lets less Co2 through the valve, try removing a couple of washers which should increase the gas flow and therefore increase the fps.

Al

PS: Just looking at one of the photos of the Gamo it appears to have a hole through the thumb grip on the hammer, try putting a small nut and bolt through this to increase the hammer weight, and see what happens.

aircube · Veteran Member

thanks Al, whew, i'm glad you said that. Thats what i had assumed when i had it appart the other day, so i reassemled it with one washer as per the diagram.

Seems to be working great now, esp at 21 celcius or higher Laughing

but i notice the co2 runs out faster, so i geuss the 2 less washers is working. Smile

Is it normal for the first 2-3 dry shots after a new cartridge is installed to be REALLY strong and blow co2 vapour from every where. vapour blows out the barrel, out the breech and out the slot for the hammer??