GTA
General Discussion To Gateway To Airguns => The Shop => : thebookdoc April 25, 2010, 05:19:11 AM
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I have a Gamo Big Cat with a broken spring, and I want to replace the spring with a gas ram (gas spring). I'm not looking for a spectacular change, I just want to have a rifle with a gas spring, and experience the difference in performance (not necessarily improvement). I see that several places sell a Nitro or Air Venturi for about $109 but they require sending the rifle to them for installation. I've got a spring compressor and I'd like to try it myself. However, I'm wondering about two things: price and procedure.
* Anyone know where I can get a gas spring for less than $109?
* Anyone know where there are instructions for gas ram installation? (I imagine it isn't really all that complicated, but find it interesting vendors won't even sell to people now...so maybe there is something I am not anticipating?)
Thanks!
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Interesting, PA used to sell just the rams for DIY installers. This is a wild guess, but I suspect it has something to do with Crosman now owning the Nitro Piston rights.
The only other alternative I know is a Theoben ram from Dave Slade of AirgunWerks, but it's going to be more expensive than $109. Good unit, though, I put one in a Gamo CFX several years ago, back before Air Venturi and Nitro Piston were even on the horizon. Wish I still had that rifle. Nothing complicated about the install at all. I'd even go so far at to say it's easier and definitely cleaner than installing a spring, since there's no spring tar involved, just a little moly on the piston. Here's the link to AirgunWerks aka Theoben USA: http://www.theobenusa.com/ Good luck!
Dave
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I think the change to no more selling just the ram has to do with staying in business.
Last year, I bought an air venturi gas (spring) ram from PA to install in my Whisper. It came with no instructions for how to install it, and for what details/mods were needed for what current model gun. Mine being a later production Whisper, apparantly had some differances from earlier ones. I found that out by reading details of what some others posted about what they had to go throught to install one in their Whisper.
I would assume that as a result, PA got fed up with all the phone call questions and possably loosing money running a gas ram installation school over the phone. Having been in a similar situation, I made the mistake of selling carburator rebuilding kits I hand made. I lost more money than I ever made by spending countless hours on the phone trying to teach people who know nothing of how a carb even works, how to re-build one. Yes, I could have done a detailed "how to" sheet but it still doesn't teach how to use tools and deal with every other problem that pops up even if it has nothing to do with carbs. Sell a kit and you own every problem with that gun/car/whatever, no matter how remotely connected. So, if that's the case with PA, I can understand why they would now say we won't sell ram kits, just send us your rifle if you want one installed.
At least that's my guess for the change.
Paul.
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Hey bookdoc,
I just sent another PM.
Andy Wong aka larspawn
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lars... it must have got cut off -- I checked and see nothing... send to thebookdoc@aol.com as well!
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do they make one for the talon mag?walther type?
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Got a response back from Theoben...They said:
"Theoben make one that fits the Gamo Hunter 440 and the CFX -- they are $145 plus shipping -- however, I never taken a Big Cat apart, so I cannot say if it would fit, sorry."
Any idea if the hunter440/CFX ram would fit a Big Cat?
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Thanks for the offer, Andy. I'm just interested in converting this so I have a gas ram on hand. It may cost almost as much as a new rifle to do ($145 for the RAM!!), but I got it with the intent to add the gas ram. Good thing I got it for nothing.
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I just read on another forum that a gas ram can be installed in the Big Cat. I sent a query asking him which model would fit. If he comes back to me that says the CFX one will fit, then you could probably get the Theoben.
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Hey, thanks for that! I look forward to hearing either way, and deeply appreciate the extra effort!
Richard
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Get your gas ram here - http://www.airgunwarehouseinc.com/crosman-nitro-piston-springs.html I don't think they require you to send your gun to them for the conversion.
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Or splurge a little and get the Theoben gas ram. It's a much nicer gas ram with a smoother cocking effort, but shoots pellets faster. Installation of the Theoben gas ram is reverse what it is for the Air Venturi and requires you to shim around the gas ram body with tape so that it is a snug fit inside the piston sleeve in the rifle. I already have 2 CFXes with synthetic stocks (.177 & .22 cal.) fitted with the Theoben. I have third one coming for my CFX Royal that has the Air Venturi gas ram in it. I did a side-by-side comparison between the Theoben .22 and the Air Venturi .22, and that is how I know the Theoben is a superior gas ram. It shoots 14.3 grain pellets at 725 fps (close to the rated 750 fps) with lead, whereas the Air Venturi CFX shot the 14.3 grain pellet at 680 fps.
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Reading the listings in the link LongIslandArcher posted, it says the gas ram that fits the Whisper is the same one for the Big Cat and other Gamo's.
http://www.airgunwarehouseinc.com/py-a-2103.html
"....Fits Gamo Whisper-series,Hunter Sport,Varmint Hunter,Big Cat& ..."
If it's the same Air Venturi I put in my 22 Whisper, you may find as I did that it's not going to be as powerfull as you hope. Jumbo heavies at 595fps, Jumbo 15.8gr at 620fps, Superdomes at 686fps. Very consisant velocities, and very accurate with Jumbos, good for back yard hunting and plinking, but not the power and range I wanted for hunting in woods and hay fields.
Paul.
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That's why I recommend going with the Theoben.
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yes, and I'll probably be going in that direction...Theoben that is. Just wish it wasn't $140 more than I paid for the gun ;-)
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You're still ahead if you're getting a Theoben gas ram gun in the end for only $140. BTW, the Theoben is $145 plus $10 s/h and David Slade only takes checks or money orders. Checks take an extra week to clear whereas a money order clears right away and you'll have your gas ram in about week after you send him payment.
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i don't know if i would pay the extra since i reversed my crosman ram in my gun and did get better fps but found the recoil to be much more i think in my opinion there is no difference in quality between the two other than theoben found that by reverse install privided more fps. think about it there is alot of weight slaming forward with the ram body doing the moven much harder on the gun and all it's components now this would be exceptable for a quality made gun but as for gamo's i would keep the violent recoil down or your asking for trouble.
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OK let me play the "bad guy" on this thread. I don't think putting any kind of gas ram/ strut system in this rifle is going to be much of an improvement in the over all performance. It just doesn't seem to justify the cost either. Also being a lightweight hollow bodied stock isn't going to make the situation any better. Ex you want to know why the Beeman RX-2 is such a heavy rifle,....because the Theoben gas ram is so strong, that accuracy will suffer without a solid platform (dense heavy stock) to shoot from. But getting back to the Gamo Big Cat, I'd recommend tuning it with a Maccarri spring and seal for the fraction of the cost and enjoy the rifle for what it is. tjk
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TJK, I appreciate the sensible suggestion. As my original post says, I'm not really worried about performance. It comes down to a learning experience. I have springers. I have some excellent springers (in my estimation). I don't have a gas ram. I hear the kick can be pretty stiff. I hear a lot of things. HOWEVER, if I don't experience them, then I don't know what I am talking about. Is the recoil from a gas ram different from a spring? It is from what I hear. If I give advice on rifle scopes and someone asks me about putting one on a rifle with a gas spring, I can't rightly recommend anything I've tested just on a springer. One of my new hobbies is testing scopes on springers to see if the ratings really hold.
If I were just fixing the rifle, you are right...I think I'd just put in a new spring and be done with it. However, there are rams made that specifically fit this rifle... I think I need to try it for the sake of experience and to have a gas-spring in my collection. I'm not looking for another investment in another rifle...I expect I need the money to buy another scope cause of the last ones I broke ;-)
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Shady, the problem you're probaby having with your Nitro Piston gas ram being installed backwards is because you didn't install washers at the end of the ram rod that would butt against the receiver tube back-plate. The Theoben gas ram has a threaded hole tapped into the end of the ram rod and two 1" dia. washers are screwed to it. Also, I suspect you also didn't shim the gas ram tube body so that it doesn't shift around inside the piston sleeve. Therefore, you're going to experience all those things that you just mentioned in your comments. My CFXes with the Theoben gas rams are stacking pellets one on top of the other.
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OK sure I see where you're coming from. The Gamos are tough on scopes for sure. I had a BC a few years back myself. From my experience with the RX-2, if it were in a synthetic stock, the recoil would probably similar to that of a Diana 350 magnum rifle. The biggest advantage with a ram is that you lose the twist and canting from the torque of the spring during the firing cycle when it's expanding. But for frontal and rearward recoil,....you aren't going to lose much at all without a dense stock, and I think that is where scopes really go through the most trauma. Synthetic stocked springers are somewhat of a different species in their own right too. Good luck with the Ram and your field testing!! Hope to hear of the results in the near future, tjk
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you suspected wrong because i fabricated all new delrin washers and ram guides to fit it in the gun backwards and i'm not saying don't do it. i just can't see paying the extra for the same thing thats all. i will say for quality sake that my crosman ram is no good it went flat on me with about 2 thousand pellets thru it.
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Shady, the Nitro Piston does have a tendency to go flat. I have a Crosman NPSS that had a failure of the piston, which I took out and sent back to Crosman for a new piston. I recently took out a Nitro Piston I had installed in one of my CFXes that started going flat on me. Whereas I was getting 980 fps with it in .177 cal. last year, I was getting 680 fps when I chronied it a few weeks ago. That's when I replaced it with a Theoben. Believe me, the Theoben is a tamer, but more powerful, gas ram than the Nitro Piston. I'm in the process of replacing all the NP gas rams from my CFXes with Theoben gas rams. If you've never laid your hands on a Theoben gas ram, then you wouldn't know that they look and feel to be of a much higher quality than the NPs.
The way the Theoben is installed lends itself to better energy retention when the gun is fired, leading to greater muzzle velocity. F=Ma - the greater mass accelerating inside the compression chamber produces greater amounts of forced air behind the pellet.
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i thought about purchasing the theoben but with all the troubles i have had with my cfx and breech seals due to the gas ram i went and put the NP into my gamo hunter and was really loving it until it went flat but it is still warrenty so PA is sending me a new one. i was getting in the low 900 with the cfx after new breech seals but it would only hold up for around 100 shoots then i would begin to see moly starting to appear at and around the rottary breech so i decided to go back to the spring in the cfx so i would have a reliable gun from time to time.i still have all the hardware i fabricated to install it like the theoben and may still try it like that in the hunter.
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Shady, when you installed the delrin shims for the gas ram body, how did you secure in place the one that goes on near the sear catch? The force of the gas ram body and piston slamming into the compression chamber would be enough to start shifting that shim up into the piston sleeve if it's not secured, causing your gas ram to bow upon compression.
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i poped off the plastic one that came on it and there is a shallow lip on the body so i fabed one with a very tight tollerence with the same nub to fit on the lip mine was very tight and it never moved it lipped over the front of the ram so it could not slide and when removed it was still fully intact with no sign of movement.
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Ahhhh...okay.