Calling all Gamo CFX experts

[oldpink]

Reposted from Airgun Gate under "Spring Compressors":

This is my first spring compressor, and yes, it will be my first effort at using one.
I used Perry's basic idea to make a version of my own.
It's not perfect, and I am pretty sure I will have to make some small modifications, such as cutting a groove in the right hand upright block for the cocking arm.
One thing I did to modify it was to cut the left hand block, then add a hinge and hasp to it, as with the right, to facilitate inserting the rifle without having to remove the front sight assembly.
As you can see, I already have two carabiners to keep both hasps secured.
It's a bit crooked and certainly not as pretty as Perry's, but I am eager to use it for the first time.


Total board length - 40"
Right side of board to right side of right upright - 14.75"
Distance between uprights - 16.5"

Anyway, I will be using this pretty soon to do a complete tune and seal job on my .177 Gamo CFX, which is definitely showing signs of being sick.
The most obvious indicator is that the muzzle velocity for the JSB Exact has declined from 750fps to 600fps.
And, yes, both of my Gamos wear Bob's magnificent gold trigger, so they are both tunable.

I just have some questions for those of you who may have done this job on the CFX:
1) What exact parts do I need from Jim Maccari, including the seal for the transfer port?
2) What additional hand tools will I need for this, such as polishing stones, pin punches, etc?
3) Are there detailed instructions here or elsewhere to explain each step for tuning the CFX, especially that tricky transfer port seal?
4) Since I also have a gas ram CFX in .22 caliber, is it any different to do the tune only on it and keep the ram?
5) I assume I will also need some lubricants especially formulated for airguns, so what will I need, and can I get them from Maccari, or is there a better (i.e. cheaper) source?
6) What special little tricks specific to the CFX are there that you gurus might know?
7) Is there anything else I should know or need for this job?

Thanks, guys.

[daved]

Looks like you're off to a good start.  And it sounds like you either have a tired spring or a bad piston seal, although the rotary breech could also be contributing to the problem.  On to your questions.

1. Springs and piston seal you can get from JM, he's finally offering a package deal for Gamo shooters.  It includes a spring, both an Apex and Tesla seal, and lubes.  If you want a direct drop in, use the 3650 spring, if you can make a custom guide, I'd go with the Tarantula package.  Breech seals are only available from Gamo, and you have to twist their arms to get them to admit it.  If you run into problems there, contact me, I have some spares, and I also have some proper sized orings for the rear of the rotary.

2. Not a lot of tools needed, I mostly use a set of needle files and fine sandpaper, sometimes a small diamond stone for deburring.  Some small needle nose pliers make removing e-clips easier.

3. None I've ever seen, although I believe someone posted a pretty good pictorial over on the Yellow Forum a few years back.  You might be able to find it by doing a search, I've looked, but this was a very popular rifle for awhile, so there are pages of CFX posts :-).  Funny how these things go in streaks.

4. The only difference is you don't put any tar on the ram :-).  Treat the piston seal the same, although I'd suggest using a Tesla seal with the ram.  It's tougher, and will tolerate the faster shooting cycle of the gas ram better.  It will probably need sizing.

5. See answer 1.

6. My special trick for the CFX has to do with the rotary breech, specifically, where the oring rides in the compression tube.  Most tuners suggest honing the compression tube to somewhere between 220 and 400 grit, which is fine for the piston seal, but I feel it's too rough for a good oring seal.  I made up a special sanding arbor that was just a little longer than the rotary, and polished out that end of the comp tube to 2000 grit, close to a mirror polish.  Do that end FIRST, then slip the rotary back in, without its oring, and hone the rest of the tube to whatever you prefer.  The rotary will act as a block, preventing you from possibly damaging the work already done.  For this to be worthwhile, you MUST do a very meticulous job of deburring all openings in the comp tube, the oring is quite small and VERY easy to damage.  I also used 100% silicone grease to lube the oring, either divers or dielectric grease will work fine.

I've only done this once, on a CFX I ended up installing a Theoben ram in, and it took a couple of tries to get it right.  But that rifle was doing right at 900 fps with Superdomes when I was done, and was extremely accurate and easy to shoot.  In fact, it was such a pleasure to shoot that I had to give it to my brother, just to force myself to shoot my then new to me HW 77.  Some have also increased the size of the oring groove, but there's not a lot to work with there, and you have to have a lathe.

Not directly related to tuning, but if you haven't already stuffed the hollow butts of your CFX's, you might want to consider it.  It helps quiet them down, and you can add weight to improve the balance and help reduce recoil.  I favored duct seal in mine, but others like to use memory foam, or even expanding insulating foam.  Just make sure you plug the forward end of the cavity, it's open to the trigger mechanism and could cause you some grief if you don't :-).

If you have any other questions or there's anything I can help with, feel free to email me direct.  Good luck, and keep us posted.  Later.

Dave

[oldpink]

Huge thanks, Dave!
I guess I need to call JM to find out what package deal I will need.
I have no real shop tools to do anything more advanced such as spring guide making or other things of that sort.
Just basic hand tools and the new spring compressor.
I'll let you know how it goes once I finally get the job done.
Again, big thanks to you.

[oldpink]

I called Gamo directly, and they provided this part number as appropriate for the rotary breech on the CFX.

http://www.gamousa.com/product.aspx?productID=184

I was surprised that they didn't try to keep it from me.

[daved]

Back in the day, Gamo maintained that you had to disassemble the rifle to replace the rotary breech seal, thus voiding your warranty, and therefore they wouldn't sell you the part.  I guess enough of us called BS on that that they had to admit it could be done.  It's worth noting, though, that none of the seals on the site say they fit the CFX.

Speaking of which, I suggest you call back and verify that part number.  I have a CFX and an 890 sitting here, I just checked, that seal will fit the 890, but the CFX seal isn't even close to the same size.  Also, mine is a translucent yellowish color instead of black.  So welcome to the wonderful world of Gamo customer DIS service :-).  If memory serves, the ones for the CFX are a part number that isn't even listed on the web site.  BTW, I have 3 on hand, so if all else fails, let me know, I'll be happy to stick one in an envelope and drop it in the mail for you, along with a rear oring seal.  Later.

Dave

[oldpink]

Thanks for the offer, big time.
I already ordered it, so I may well be out $10 because of this.

I'll just have to see once it gets here.

[oldpink]

I just found Bob's explanation of how to do the rotary breech seal.
http://www.charliedatuna.com/airgun_docs/Gamo%20CFX%20Breech%20Seal%20Repair.doc
It's a little foggy on the details, but it appears that the seal could possibly be gotten at an ordinary hardware store, just as long as the dimensions are right.
I'm not knocking Bob on this one, but his document is a bit ambiguous.
Maybe he means that "M&Carr  #9262K132" is the correct part number.
Also, are the front and rear seals identical?
It's all very confusing at this point, and the very real likelihood that Gamo just sold me the wrong seals sure isn't helping any.

[daved]

Don't worry much about the new seals Gamo sold you, if they are the wrong ones, I'll be happy to take them off your hands.  I have an 890 that I'm going to be doing a lot of work on, so having some extra breech seals on hand would be a good thing.

I doubt you'll have much luck getting the oring at a regular hardware store, it's a metric size, and I've yet to find a local source that carries metric orings.  Even NAPA is no help there.  McMaster/Carr is a good source for that kind of stuff, I'm putting together a shopping list for them right now :-).  Orings, spring wire, lathe tooling, the list is getting pretty long.

Just to clear up the confusion a little, the rotary has only 2 seals, on the barrel side is the breech seal, and at the rear of it is an oring.  That oring is by far the weakest link in an otherwise excellent rifle.  If you have a .177 CFX shooting in the 700's or less, chances are good you have a sealing problem.  Other than the rotary, it's the same power plant they use in the break barrel rifles, and they're 900 fps guns pretty much out of the box.  There's a little loss of efficiency due to the increased head space of the rotary, but the CFX is still quite capable of hitting the 900 fps mark with some work, and shoots very nicely at that level.  So don't give up, we'll get you through this :-).

Email or PM me your address, I'll send you those seals just to make sure you have the right parts on hand.  Later.

Dave

[oldpink]

On the subject, I left an e-mail inquiry for J.M. to determine exactly what kit I need to do the tune, but I have yet to hear from them.
I understand that Maccari is the best in the business and practically the only game in town for tune components, but I have to say his web site is harder to figure out than Chinese arithmetic.
He could use a major rework of his entire site so that those not yet well versed on the subject can go straight to what they need for the job.

[daved]

JM considers his primary customer base to be professional tuners, and figures that if they don't know what they need, they should be shopping elsewhere :-).  I wouldn't expect a quick or helpful answer back, but he might surprise you.  Since you're planning on a full tune, you'll either need this: http://www.airrifleheadquarters.com/catalog/item/251488/7718385.htm  or this: http://www.airrifleheadquarters.com/catalog/item/251488/7910058.htm  As you don't have a way to make a custom spring guide, I'd go with the first kit, and use the Apex seal.

Your only other option is to go through his site, checking the specs on each spring, and choosing the one you think will do what you want.  I've done that, it's fun, but time consuming :-).  Later.

Dave

[oldpink]

It looks as if this is an alternate source for the seal, at least according to Bob's page I linked in an earlier post on this thread.

http://www.mcmaster.com/#9262k132/=94mlsu

$7.77 per pack of 100.
I could order them, keep about a dozen for myself, then dole out the rest to any deserving souls out there.

[oldpink]

Huge thanks for the links!

[oldpink]

Daved, since I also intend to tune my gas ram CFX, I won't need the spring, but won't this seal here work?:

http://www.airrifleheadquarters.com/catalog/item/251485/2325552.htm

Am I right that the Tesla is a bit more durable than the Apex?
If so, will it still require sizing, and if so, is it very difficult to do that?
I feel like the quiz kid at this point.


I also went and ordered these for the breech:
The front - http://www.mcmaster.com/nav/enter.asp?partnum=9262K122&pagenum=3460
The rear - http://www.mcmaster.com/nav/enter.asp?partnum=9262K132&pagenum=3460

I also called Gamo and had the seals I ordered under their suggestion, since they were the wrong ones, and had the order canceled.
You will be amused to hear also that they tracked down the part number for the front seal, and they were willing to ship that freely, but the rear seal would require shipment to an FFL holder only!
Ridiculous, so I bypassed them entirely, using Bob's document about the seals and found them on McMaster-Carr's site instead.
Since you were nice enough to send a few that you have, the least I can do is to ship you a dozen of each that I ordered from McMaster-Carr.
Will do that once they arrive.

[daved]

I think the Tesla seal is a good choice for the gas ram, and will be about all you'd need for a gas ram tune.  If you ordered either of the kits I mentioned earlier, you get both an Apex and a Tesla seal, no need to order an extra :-).  For best performance, it will probably need sizing, but if you have a hand drill, you can size a seal, you'll just need to make an arbor to hold it.  And that can be as simple as a bolt, some washers, and a nut.  It's a harder material, so it's a bit more durable, and stands up better to the higher piston velocity of a gas ram.  However, because it's harder, it's not as tolerant of out of round compression tubes, and it takes a LOT longer to wear in if you don't size it first.  Makes for a tight fit, and reduced velocity otherwise.

Good deal on the McMaster\Carr stuff, I'd completely forgotten about that info on Bob's site.  Glad to hear you got the Gamo order cancelled, what they consider customer service just boggles the mind :-)!  FFL holder only, huh, that's a new one!

The stuff I promised went out today, got jammed up yesterday, sorry.  Hopefully, you'll see it by the end of the week.  Certainly don't need a dozen ea. of your new ones, just a couple of each would be great, thanks :-).  Later.

Dave

[oldpink]

Posting this here, since I also PMed it to the extremely generous daved.

Whew!
I finally managed to get the job done.
As it turned out, the rear rotating breech seal was torn, and the piston seal was nicked.
The mainspring was also broken at about the second coil from the tophat end.
I hope I was able to get the brand new Apex seal in without doing that, but I honestly see no way to avoid it, since the cocking slot in the compression tube is bound to do it a bit, no matter how much I tried to sand away any rough spots.
That was another thing that really was tough for me: sanding away any burrs, at least in those extremely tight spots, such as that cocking slot and inside the compression tube itself.
I finally just wrapped some fine sandpaper around a broom handle, then sanded out the inside of the compression tube the best I could under the circumstances.
I also had to buy a new bar clamp, since the 36" Bessey model I had was about four inches too short.
In fact, since I was working on it in the evening, when the stores were closed, I actually used my own brute force to push the receiver against the screw end of the clamp, then nearly killed myself pushing that end hard against my chest until I just managed to get the muzzle onto the opposite end of the clamp...all four inches of spring force at that!
Left a bit of a nasty bruise in the process, but I was just able to just barely get the compression tube locking pin in place.
Along with being about four inches too short, the Bessey bar clamp also has too short of a travel distance for the screw, only about 1.5"-2" at most, definitely not enough to make it a workable clamp for the job, even if it had been a 40" clamp.
I returned to Lowe's this afternoon, hoping to find a 40 incher with a much longer screw travel.
I left, dejected, since they had two that were over 40", but they had the same puny screw travel, making them useless, plus they cost a whopping $50-$60.
I then went to Menard's, hopeful, but about to resign myself to not finding what I was after.
I found a Jorgensen brand model 7248 clamp that was a giant 48", had a bar so stout that it could be used to crush a cannonball, had a huge full length cast iron clamping surface on the screw end (much better than the screw sized clamping point on the Bessey) that extends all the way down the clamp bar, and (yes!) had a very generous 3"-4" of screw travel.
A bit expensive at $35, but this beast was the thing for me!
I took it home, then performed some major surgery on my undersized spring compressor to accomodate this monster, then went to work to take out the locking pin and release some of the spring tension enough to insert the trigger group, since I had only wanted to put the spring under tension without reassembling it until I had fixed my compressor.
I also had to reassemble most of my trigger, since I had accidentally allowed the sear pivot bolt to pop out, which forced me to learn exactly how a Theoben trigger goes together.
I was only halfway there and stumped, then a quick web search turned up this lifesaver of a page:

http://www.airgunfix.com/blog/airguns-assembly-disassembly/gamocrosmanchinese-trigger-group-disassembly/

Whoever put that page together did a fantastic job, because even this little old novice non-mechanic was finally able to get it all back together.
I reinserted the trigger, compressed the mainspring, then put the locking pin back in place, all with ease.
I finally was able to get it reassembled, but in the process, I accidentally sheared off the head of one of the two forend screws.
Oh well, I think I can either get one in an ordinary hardware store, or (blah!) try to beg Gamo to sell me one.
Either way, there is enough of the screw remaining that the stock stays put for now, so I test fired six or seven pellets.
It sounds good, but (predictably) there is the smell of oil smoke from the moly and (probably) the bit of heavy tar I put on the spring itself.
Tomorrow, I will see about putting a couple of dozen through it, and chrony it to see how she's doing.

The new compressor with the giant Jorgensen clamp is what I should have made the first go around.
Here is what it looks like:
http://www.adjustableclamp.com/bl-7200.htm

Oh well, maybe I can get rid of the "puny" 36" Bessey clamp in a yard sale.
I know from now on, I will recommend to anyone who asks how to make a really good compressor that he start with this 7248 Jorgensen monster.

[daved]

Sounds like it turned into a bit of an adventure, Scott :-).  Just for future reference, you don't need a clamp that will reach the end of the barrel, in fact, that's exactly what you DON'T want if you were working on a break barrel.  Something like this works well, and requires a much shorter clamp:



The first gun I worked on with this setup was a CFX, followed by a Diana 350.  Used it again yesterday to take apart a Gamo 890.  Regardless, I like the screw travel on the clamp you found, looks like mine is finally going to get the upgrade I've been threatening for the last several years.

For working on the compression tube cutouts, a small set of needle files is the answer, all you need to do is break the sharp edges left from the stamping operation.  But sandpaper and broom handles would work, too :-).  For getting the seals back in, I go slow, and use a small screwdriver with all the edges dulled to help them across the potential damage areas.  I find the transition areas the most difficult, areas where the slot or other opening ends.  I suppose if you were doing a lot of them, it would be worth having some very thin shim stock on hand, just to cover the slots as you slide the piston and rotary in.

Those triggers can be a bit tricky, getting the springs oriented properly can be a real PITA.  That same site saved my butt just a short time ago.  I still need to do some more work on my 890 trigger, but I'm off to a good start, more on that later, in my own post.

You should be able to get the screws at your local hardware store, they're a standard size.  I know Gamo has used both Phillips and Torx screws for those, I'd suggest regular Allen heads, and change them all.

A little dieseling is normal after a tune, it's almost impossible to reassemble a springer without getting a little lube in front of the piston seal.  I should go away shortly, and you can accelerate the process by shooting a dozen or so heavy pellets.  Not sure why that works, but it does.  I'll be interested to hear what your chrony numbers are now, especially considering the damage you had to start with.  Don't be surprised if it develops a preference for a different pellet than what it liked before.  And congratulations on your first tune!  Trust me, it probably won't be your last :-).  Later.

Dave

[oldpink]

Just fired somewhere around over 50 pellets through it to try and break it in a tiny bit and try and purge some of the excess lube.
Tested MV of the Crow-Magnums was in the 770fps region, right where it was when this rifle was brand new.
Unsure if the smoke indicating some dieseling (no detonation, though) might be affecting velocities, but I fully expect that to be negated after the excess lube is burned off, since it should be more fully broken in by then, giving me (I hope) comparable MV and (more importantly) consistency.
This is a huge improvement over pre-repair, since I was getting in the 600fps range with the lighter H&N Silhouette at that point, and to get in the 770 range with the much heavier Crow-Magnums leads me to believe I can achieve at least that or even up in the 800fps range with the Silhouette pellets.
Time to get a replacement forend screw, then wait until Wednesday to go for an extended shoot to knock out the remaining excess lube, break it in a bit, then sight in once the smoking stops.