Canadian Airgun Forum

How is the piston seal sticking? Like you have to slap the rifle to get it to fire?

Don't take dukes comments to heart. But don't forget, experienced advice is usually golden. In my fields of work I always prefer to learn from the old timers. They know what they're talking about. Once you get some pimply kid showing me how his phone app knows better and starts whining about work/life balance I lose interest really fast.

Pretty soon I'll be the old timer.

I myself am learning the differences between a cheap gun and a much less cheap gun. The principal is still the same, but the engineering is much better. You get what you pay for.
You take a $150 rifle, spend money and untold hours of free time on it, and you get a nicer version of the same gun. Spend more money initially, say $500. You have a better design, higher quality materials, and usually better fail-safe methods built into the gun. (Have you ever seen the cocking rod setup on a hw50? That my friend is impressive). But, at the same time, there is still room for improvement. Guides, pistons and springs in these higher end guns are still mass produced and not actually mated to eachother. So where does a guy draw the line? If I were to spend $1000 on a rifle and the internal parts weren't properly fitted I think I'd return it. That's my opinion though.

Hey if it makes you happy, keep on keeping on. You'll learn as you go and your methods of doing things get better. That's the fun of this hobby

It's sticking like the compression chamber is too narrow. So I've just opened it up, again, 3rd time and I haven't had the damned thing for 24 hrs. And I gave it a good sanding, first time for that little trick. I've just got it back together. Gonna give it a shot.

Yeah, first used rifle I've bought. I may be learning about cheap. I think this one can shoot straight, I've just gotta push them through.

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Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Well, I got 15, maybe 20 shots. It started sighing again.

I only have a bit of 240 and 400 grit. Might be a good time to resupply.

I might try putting my sanding rod in a drill next time

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Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Maybe go to Cambodian tire or princess auto and pick up a brake cylinder hone. Cheap. Should be under $20. Not only will it hone the cylinder but it'll help you identify dents and swells in the tube.

But it sounds to me like your seal is oversized.
What is the condition of the dovetail on the piston face? If it's hammered out or deformed your seal will also get stretched out.
Unless you got a dent in the tube... Or a bend. The only time I ever had a piston that sticky was with a maccari seal I bought and threw in the gun without sizing it. Then I learned about sizing piston seals.

Reduce the diameter of the seal. You shouldn't need to hone the compression tube unless it's corroded. The piston should be able to drop down the compression tube by gravity with a slight assist from your finger. I'll bet it's a lot tighter than that.
There are threads explaining how to reduce the seal diameter.

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Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

The only compression tubes I have had to hone were my two .177 Chinese B3s. Both had corrosion in the tube. My recently acquired .22 WF600 (B3-4) needed no honing.

_________________
Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

Thanks guys. I'll be having a good look at the seal.

I don't mind opening it up so much, or the work. I just don't like not knowing.

Something else I've noticed is that the barrel is squeezed real hard at the hinge point. It's a job squeezing it back in, shaves come off the washer.

We'll see

_________________
Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Bummer. Not the seal. Woulda been easy, right? I checked it against my newer short piston and seal, a fresh seal and an old one. All the same, piston too, but longer. And there was lube in the chamber.

I checked the inside diameter of the tube at the trigger end, .9875", do you know is that the spec?

I may do sanding tonight. And check for true.

Cheers

_________________
Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

I just opened up my phantom for you.
I get .987 with my vernier calipers. Where's the problem, the compression tube? What are your seals measuring at?

Here's a guide and end cap I made a couple weeks back. Was bored one night lol

Do us all a favor and measure the dovetails on the pistons when you get a chance.

When you measured the seals, were they installed on the dovetail on the piston? The outside diameter of the seal should increase slightly when installed on the dovetail. Killer's measurement confirms that your compression tube is the same diameter as his. How much bigger is the outside diameter of the installed seal as compared to the inside diameter of the compression tube? Does the piston need more than slight finger pressure to slide down the compression tube?
This one has me scratching my head. If it isn't the seal-tube fit, maybe the liner is shifting in the piston and creating enough extra friction that it is affecting an already very weak spring. Try reassembling it without the liner and see if that makes any difference. I have found liners that are tight do slow down the piston. That's why I was squeezing yogurt containers...

_________________
Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

That’s some nice work, killer. Purty. I’d like to have a couple of your or Rick’s tools, a little step up from my cordless in the vice. I ain’t complaining, tho.

And I’ve thought of that piece in my Optimus. We’ll see. Back at work today.

Cheers

_________________
Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Well Duke, I have to concur, my rifle shoots like crap. I’m not giving up on ‘er yet tho.

I still want you to show me the money. You know, what you’re doing now, what you know about pellets, your targets and stuff.

Cheers

_________________
Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Yes, I’ve thought of it. Eyeballing it I thought maybe the seal, or the dove isn’t centre on the piston.

And I’ve done a quick check on the outside of the tube for true, but I’m going to have a much closer look at that too.

When I pull the piston out after it stops shooting, and I look in the tube and at the oil on the seal, I get this idea that there’s a distortion in there, some kinda wow or something.

Anyway, when I get home. Thanks

_________________
Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

Hey fellas

I'm gonna get my caliper and start measuring shortly.

Here's one to keep you entertained, it's how I left it last night. My cheesey compressor! Works great, tho, really.

Later

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Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40