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PostPosted: Sat Jul 14, 2018 5:33 pm 
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Joined: Sat Jul 14, 2018 5:16 pm
Posts: 3
Had a lapse of judgement and I now have two holes where there were only two smaller ones. I originally intended to tap and screw one hole shut since that's how I thought this gun was originally detuned since the spring and piston are proper sizes and it's sold as 490fps.
So I just want to know if i have done too much damage to salvage this piece or whether there is a way to fix the gun. As of now, once cocked, the spring releases and it feels like there is a good shot but the pellet does not move any further in the barrel.
With the bigger hole ( the one that does not line up with the barrel) plugged, it also doesn't help propelling the pellet any further.

Any help is appreciated. Thanks.


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PostPosted: Sat Jul 14, 2018 6:02 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2778
Location: Somewheres near the Atlantic
Its pooched. The bottom hole is for the barrel detent to lock up. Top was the transfer port. Where the slamming piston pushes air thru and the pellet out the barrel. Without the lock up, I bet it's not getting a good seal and leaking there.

Unless you got a tig welder to fill the hole and lathe to re drill the port. Its cheaper to buy a new one.

They're detuned by lighter coil weaker spring, or full power with a relief hole in the piston.

You can call crosman dealer in Canada and see if they can get you a new one, but might as well if you got a PAL find one already full power.


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PostPosted: Sat Jul 14, 2018 6:42 pm 
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Joined: Sat Jul 14, 2018 5:16 pm
Posts: 3
I'm a cnc'er and got access to the Tig welder and a lathe.
Could you go into more detail what I'd need to smooth out and am I welding the hole shut? Are these holes designed to just go through straight?
Also, the transfer port diameter is almost exact same as barrel diameter (.210 vs .211) and I was able to plug the other hole with a screw that definitely sealed it. All that had no effect.
Also there are no holes in the piston it's not larger than full power (5 7/8 from my memory) and the spring is 36 coil and that's what I read as being the full power one.
Appreciate the advice


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PostPosted: Sat Jul 14, 2018 7:08 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2778
Location: Somewheres near the Atlantic
NickelRigger wrote:
I'm a cnc'er and got access to the Tig welder and a lathe.
Could you go into more detail what I'd need to smooth out and am I welding the hole shut? Are these holes designed to just go through straight?
Also, the transfer port diameter is almost exact same as barrel diameter (.210 vs .211) and I was able to plug the other hole with a screw that definitely sealed it. All that had no effect.
Also there are no holes in the piston it's not larger than full power (5 7/8 from my memory) and the spring is 36 coil and that's what I read as being the full power one.
Appreciate the advice


First you need to fix what you messed up. Because no matter what size spring you used. its not going to make ANY speed.

You basically gotta add metal that you removed. And reverse everything you did.

Well your going to need to find the factory crosman port size ( 1/8th inch ). Your going to need to weld up the hole so you can re drill it to the proper size and make sure the breech face is smooth so it doesn't rip the breech seal apart when you close. Or rip up the piston seal. Yes they go thru and thru.

Appears you removed and opened the hole for the barrel lock. Your going to need to put that back so the barre locks up.

The piston slams forward compressing air and making pressure IE thru the small hole. The air goes the path of least resistance. Too big of a hole and makes no pressure.

Nothing on the tube needs to be plugged. Also how thick is the coils? you can have a 36 coil spring, if the coil wires are thinner, than well its going to take less effort to compressor.

I upgraded 2 ways of a phantom were detuned.

Actually there is 3 ways.

Longer piston, shorter spring.
Full power spring with short piston with relief hole.
And short piston, with weaker spring.


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PostPosted: Sat Jul 14, 2018 7:55 pm 
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Joined: Sat Jul 14, 2018 5:16 pm
Posts: 3
Thanks for the info, I will weld up the holes closed on Monday and will Post some updates. Also, I attached the picture of the view from the receiver.
Here are some measurements. I think the detuned might be the option three you stated.

Spring: 9 3/4 length, .1 coil thickness, .730 coil diameter
piston: 5.718 length

Lastly, you know the hole diameter that I'll need to make after I close it up? I'll check crosman site and see if I can find it there too.
Edit: sorry just re-read your post and seen the size.


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PostPosted: Sat Jul 14, 2018 8:54 pm 
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Joined: Thu May 07, 2015 8:30 pm
Posts: 1184
Location: Eastern Townships
On these Crosman rifles, there are two types of locks used in the receiver tubes: a cross pin lock, like yours seems to be, and a wedge lock, which is pressed in the bigger hole under the transfer port hole. Both styles of tubes look to be drilled for the wedge. That bigger hole originally didn't went through the compression tube end wall, but it seems you drilled it through - not good.

If you work in a machine shop, you can make a threaded plug to plug that big hole, just make sure it's flush with the inner wall of the comp. chamber so the piston doesn't hit it. And you could also make a threaded bushing for the transfer port, ID 1/8'', OD made to fit the threads you did in the TP, again make it flush with the inner wall face. Seal and lock both parts with red Loctite, and face them flush with the breech surface and smooth them so the breech seal have a nice surface to seal.


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PostPosted: Sun Jul 15, 2018 3:52 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
Awesome! Sorry but I had to chuckle at this oopsie. Jumping in with both feet can be risky, but you learn more and do more than those who are too chicken to do so. For me learning by trial and error is more valuable than what misc things I ruin during my efforts. Plus you learn even more trying to fix these mistakes. So I'm glad you're willing to try and take chances to mod it. In this case you'll need to do some fixing :) I know how to fix a lot of stuff b/c I've broke a lot of stuff in my attempt to modify. So I'll tell you what I think, then you can decide how you want to go about it:
The bottom hole does nothing but since you drilled it all the way thru you'll need to put a plug in it so it can do nothing again. The top hole, which was the transfer port, xfer for short, needs to be ~.125" in diameter. It should be inline with the bore. This hole is how the air gets out and pushes the pellet. The xfer port dia should be ~.125" (eom) to a max of ~ .136". That dia is important but I won't get into that here, just try to keep in that range.
Imo you should not fill the hole it with weld, but instead plug it. Reason is it would be too hard to weld it correctly. You want the inside surface to be more or less like it was, which is flat and flush. So I'd drill/tap the holes to whatever size is reasonable, then thread in a bolt as a plug. You'll want to make the plugs face on the inside nice n flat, and of course thread it in so it's flush in there which is doable but a pita considering its location. I'd use a stick to feel... The lower hole can simply be a set screw since the other end doesn't matter, it's only purpose is a plug. The top hole needs that xfer port and needs to be flush with the breech surface. So this one needs to be cut/sanded the exact length so it's flush with the metal on both sides. I'd trial and error the length by removing a little at a time until perfect, then use loctite. The xfer port needs to be pretty much where it was and I assume that'll be in the center of your plug. I suppose you could drill two small holes in the plug so you can use a spanner type wrench to get said plug in n out, as long as you fill the holes with epoxy when done. I'm picturing a wood or alum rod with two little steel rods sticking out a mm as your wrench? Optionally you could use the xfer port to turn the plug as long as you don't damage the hole. As long as the threads you made and the plugs threads are nice it should thread in n out easily, but usually bolt threads will need touching up first, or run a die over it. To clean up bolt threads I use a tiny three sided file, then wire wheel it.
Reason the plugs need to be flush inside is if they stick out the piston will hit them, which is really bad. If recessed then you lose compression, which is how some guns are detuned. If the plug with the xfer port is recessed on the outside (pellet side) you'll again lose compression. If out too far it'll tear up the breech seal. The loctite, or sealant used be liberally applied so it fills and seals completely. The breech face side may now have a seam where your plug is and may leak, so I'd use epoxy like bondo to fill the seam, then sand it flat so the seal won't know the diff.
Btw, no doubt your power was reduced via a weak spring. The full power spring has .122" wire, which you can buy from the gravel agency for ~$13CA. If you want a whole new receiver/compression tube they should be ~$36CA. I'd fix it which is both challenging and a learning experience.
Another option if you wanted; you could also cut the tube from the breech block, which is welded now, then you could weld the holes and make the inside surfaces perfect, then weld it back together. I'd still use a plug since actually filling the hole with pure weld would be a pita. Of course this would ruin the finish so you'd need to deal with that, like maybe paint it? Cold blue is kinda sketchy looking and will rust much easier than the oem bluing, but I did an entire rusty shotgun in it and it came out fairly well. I had to sandblast the entire surface to get the rust off and make a surface the cold blue liked, which ended up being matte black and looks alright.
The xfer port should ideally be very smooth so I sand them. Usually the oem hole is very rough so I often drill to .127 or .136 before it's smooth enough to sand. In your case I'd drill .125 carefully so you don't make a mess like the factory did, then sand it nice n smooth with 400grit wet/dry paper which I tape to and wrap around a stick and spin with a drill. I also put a little bevel on the inlet side of the port which would be much easier to do with the plug in hand. I have a tuning guide if you want, which covers lots of things you can do, what needs fixing and how to do it; chevota at hotmail


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PostPosted: Sun Jul 15, 2018 5:56 pm 
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Joined: Mon Aug 26, 2013 12:19 pm
Posts: 103
Location: Alvinston, Ontario
When Chevota has written about springers, I'd do it.
RWS 350, Diana 24, 3 Ruger Airhawks, Slavia 631, 2 Stoeger X3's, all tuned the way he suggests.
Neighbour wants to trade his gun plus money for my "Chevota" gun.
All were done on the cheap, just had to take my time.

Follow his instructions, take your time, gun will be like new, maybe better.

Chris



Sent from my LG-M703 using Tapatalk


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PostPosted: Tue Jul 17, 2018 10:26 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
cwild1971: Thanks for the compliment, and glad to hear it worked out for all your toys :) I like to hear that the info was helpful, usually I hear nothing back so I wonder how many people actually attempt the work.
I've never heard the term "Chevota gun". If I were to ever design/make an airgun I think "Chevota Magnum" sounds pretty sweet. In the past I wanted to make a wildcat round, like .458 Chevota Magnum :)

NickelRigger: Fyi I saw in an article once where someone made said threaded plugs for the xfer port in order to test various port diameters. Not sure how that helps you but it was on my mind. What I do want to add is please post pix of your actual fix b/c I've rec'd several emails from people that have drilled them out too much. Usually it's to like .150 to .170" which I suggest epoxying in a brass tube with the correct ID. Whatever/however the fix it's info others can use, plus I wanna see it!


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