Can anyone tell me..... Gamo ACCU .117

[ColdTexan]

So, I bought a Gamo ACCU .177. Love the gun! I have about 150 pellets thru it and it won't quit deiseling.

Anyone know how many pellets I am going to have to shoot before it will quit?

Anything I should do (that don't require breaking the gun down and cleaning it)?

Thank You for any help you can give me!

One COLD Texan!

[Back_Roads]

 It should be setteling in soon, What weight pellets are you shooting, if less than 9.5 grain they may also cause sonic crack.

[ColdTexan]

I started shooting the JSB 7.3 grain and it was grouping VERY well. It was only going subsonic once in a while.

I have switched to the JSB heavy pellets last night, it seams like it is worse than when I first started. I cleaned the barrel last night when I finished shooting, I hope it will help today. The patches were black.

Thank You for the reply Back_Roads

Cold Texan

[Novagun]

My experience with a Gamo CFX, which is the same as an Accu,  was that the dieseling did not stop until the grease was cleaned out and the thing and it was properly lubricated. Out of the box there was far too much grease in it. The dieseling broke the spring before I learned. Properly lubricated and with a bit of titivation you will have a good gun.
I found JSB 8.44 gn pellets to be the best for my gun.

[ColdTexan]

Thank You for the reply Novagun.

I don't know how to completely disassemble this rifle but I will take the stock off and inspect the chamber. If there is a lot of grease I can get to, I will clean what I can reach.

How is it that the grease on the spring is getting in front of the seal to make the gun diesel?

Cold Texan

[bhh]

Here's how much grease mine had from the factory.

I think the grease is getting past the seal through those rips and tears in the seal caused by the factory shoving the piston assembly into the tube without deburring all the sharp edges in the compression tube.

[ColdTexan]

WOW! My  gosh, I will have to fire hundreds of shots to ever HOPE to get that much grease out!

I better at least take the stock off tomorrow and see what I can. I don't have a spring compressor. I might have to build one.

Thanks (I think) LOL

Cold Texan

[Novagun]

You will need a spring compressor, I use a workshop sash cramp. If you can make a spring compressor you can deal with the gun. Your gun is not hard to pull apart. The best way to proceed would be to look at a Utube video. There  just has to be one on the CFX.  The rifle is just a simple piece of machinery so don't be timid, you won't stuff anything up but while you are at it replace the piston seal because you can put money on it that it was damaged in the factory assembly.
There is no need to take the rolling breach out but get all the grease out from behind it. Rags and a stick will do it. If you think it needs washing out with turpentine then maybe take the breach out because you don't want raw turps in there when you fire it. You could wash it out without removing the breach but I would blow it out with compressed air afterwards and allow time for any residual solvent to evaporate so there was no smell at all.
Getting the breach out and back in is a job that needs a lot of care but the worst that can happen is that you will wreck the o ring. A few cents to replace if you get it wrong, not the end of the world.
Re-grease using very very little grease just a light smear to stop rust, a very light smear.
If the spring twangs because of the lack of grease put a PTFE plastic wrap around the front end of the spring and assess if you need a new rear spring guide. (PTFE is a fancy name for a slice off a plastic milk jug.)

Welcome to the Gamo Accu/CFX world, the tinkering is worth it.

[OleTomCat]

Kevin,

If you are not comfortable with tearing the gun down you can message me and I will send you a quote on tuning the gun for you.

[ColdTexan]

Thank You Novagun and OleTomCat!

For many years I did equipment maintenance on restaurant equipment. I still have all my tools and the Lord knows I have delt with grease--LOL

I have decided I will build a spring compressor this week and take the gun down. I have watched a couple of YouTube videos about it and I really think it won't be a problem. It will give me a chance to sand down any burrs that I find and in the end, I will learn a lot more about springers.

OleTomCat, can you tell me where I can order a new seal and O ring?

Thank You again friends

Cold Texan

[Artie]

I liked my Accu177 so much I picked up a used one in .22 when it became available. If it's even close to accurate, hold on to it. Both .177/.22 are getting hard to find, especially the 22. People don't often let them go.
The gun's power plant Is easy to disassemble. The Achilles heel is the rotating breech o'ring. There's a fair likelihood it is already nicked. This is one springer that requires extraordinary attention to deburring all machined edges in contact with the piston. What ever the piston/piston seal contacts coming out of the gun and going back in during a tune, the breech seal will certainly come into contact with. You will likely ruin the o'ring removing the rotating breech.
Look up some of my posts on the Accu. There are probably comments about a hardware store replacement for the o'ring. Otherwise you are going to have a hard time finding a Gamo spec replacement. I use either one of two o'rings that I've found online (O'ring Store) or locally that will work. Both of them make the breech tighter to open/close but they do make for a strong seal.
Get rid of the grease or you will have recurring detonation which will likely toast your seals. The breech seal (the one on the barrel face) is very hard to source, I've no local source for them. I think the Aussie'a have one available, maybe on EBay. You can try shimming it you have the capability.
Sleeve the piston, heat shrink the rear spring guide and there's no need for the "tar" it shipped with. A light lube is all that's required after sleeving to make the Accu a "thunk" springer.
A good Accu is a fifty yard gun. My .177 loves cheap Winchester HP's and round nose.
Have fun!

[ColdTexan]

Thank You Atrie.

I called Gamo and those people are CRAZY in the head! They want you to have a FFL to ship you a piston seal! Who ever heard of such a thing on a AIR RIFLE!

I have left a message with P.A. (where I bought it) and I hope they will be able to send me one.

Cold Texan

[Artie]

I called Gamo and those people are CRAZY in the head! They want you to have a FFL to ship you a piston seal! Who ever heard of such a thing on a AIR RIFLE!

Welcome to our Brave New World.
25mm piston seal (Small Apex), or your choice of many others are easily available.

[grimeszee]

ARH sells complete gamo kits. Correct me if I'm wrong OleTomCat but doesn't the TX200 seal work?

[bhh]

I called Gamo and those people are CRAZY in the head! They want you to have a FFL to ship you a piston seal! Who ever heard of such a thing on a AIR RIFLE!

I have left a message with P.A. (where I bought it) and I hope they will be able to send me one.

Gamo's stupid policy is why I won't buy another Gamo product.

Get the piston seal from ARH and take the rotary breech to your local hardware store. A 1/16" thickness o-ring will fit on the rear. I like to get one that is slightly undersize so it has a little more tension to keep it in place when I insert it. I used a little silicone oil to get it in.

For the breech seal I used two o-rings that I stacked and glued together with superglue.  Put one in the breech groove, add a small amount of super glue, add the second, and then compress the two o-rings together on a flat surface.

Also - take a look at where the barrel threads in the tube. Mine had a sharp edge that cut my original breech seal.

[Novagun]

If the seal in the front of the breech block is damaged, and it probably isn't, I have made them out of clear plastic pipe. You need to face them off in a lathe to get the ends perfectly square.
If you want a really nice shooting gun forget the Gamo seal. I would forget it anyway. Make up a plastic adapter for the dovetail button on the piston and substitute a 25 mm Weihrauch seal. They don't come off, they are softer and better than a Gamo seal. They make the rifle a sweet shooter. Bit more expensive than a Gamo seal.
If you really want Gamo parts they are readily available here, not too expensive and the postage to the USA will not break the bank. PM me if you like but be warned Christmas is coming and New Zealand shuts down for about two weeks. 

[bhh]

25 mm Weihrauch seal.

Interesting.  Are you talking about the old style with the thin outer ring, or the newer style?  What does it do for velocity?

[ColdTexan]

I want to Thank You all for your advise and information. I have decided to go ahead and tear the gun down tomorrow. I have all the makings of of a spring compressor and will get it built in the morning. I will inspect the seals and find replacements for what I need. In any case it might take a day or so for the gun to completely dry out after I clean the grease out of it.

I think this will be a exceptional shooter that's why I don't dare send it back. P.A. already has them out of stock again and I have no idea when I could ever hope to get my hands on another. Even if they did replace it I would most likely have the same problem. I got the gun at a really good price on a sale and it is worth the effort and the small expense of getting it right.

I will take some pictures with my phone and post my results as soon as I have it back together.

Thank You all for the sage advise and information. I am new here and I can see why there are so many members!

Cold Texan

[OleTomCat]

Ok,

The Main Piston Seal is a Gamo Tesla Seal from ARH:
http://www.airrifleheadquarters.com/catalog/item/251485/2325552.htm

The Spring is an E3650 also from ARH, replace it while you have the gun apart:
http://www.airrifleheadquarters.com/catalog/item/251488/5414946.htm

The rotating Breach seal is best to get from Custom Air Seals of Australia, you will probably need to take this out to clean up under the breach so better to have them and not need them then need them and not have them...
https://www.customairseals.com/product/gamo-cfx-cfr-royal-rotary-breech-seal/

[Mole2017]

Thanks for that info Al. I was having trouble finding that breach seal myself--I figured Custom Air Seals had it, but I couldn't quite remember their name and the eBay search wasn't hitting it.

My CFX dieseled for quite a long time. Only a few were "gunshots"; usually is was just smoke drifting from the muzzle after a shot and the smell of snuffed candles lingering. I still catch the smell now and then after 4,000 rounds, but I haven't seen smoke in ages and the worst of the dieseling was over by about 500 or 600 rounds. It's on my list to tear that rifle down and do a nice job on the seals and surfaces as I put it back together.