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PostPosted: Wed Dec 01, 2021 7:34 pm 
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Location: Kingston, ON
Well I finished V1 of my 2289 Lookalike Backpacker- I have great plans for this platform.
It has steel breach, 14" Barrel, fancy muzzle brake, upgraded pivot pin - but no other mods.
I cleaned the TP, removed burrs, and polished it - its at 0.132" ID stock.
But I was surprised and disappointed with the Chrony results, consistent, but 340-345 fps with CPHP 14.3gr. 10 pumps, and it's hard enough to get the 10th in so it's getting filled.
WTF? Whats the next step.. I'd be content with 460-470 fps?

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PostPosted: Wed Dec 01, 2021 9:26 pm 
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Location: Thunder Bay,On.
so its a 1322?.....not sure what you have there but I know the Canadian backpacker was rated for only 380 fps with a 14.3...you're not far off that but I couldn't live with those numbers either... :(

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PostPosted: Wed Dec 01, 2021 9:38 pm 
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It's all here topic65054.html

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PostPosted: Wed Dec 01, 2021 9:38 pm 
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Location: Spruce Grove AB
Yeah, that's pretty standard issue velocity without using power mods. What version of valve detuning did you get?


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PostPosted: Wed Dec 01, 2021 9:44 pm 
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Hi thanks for the links and advice. I had a kind of knee jerk disappointment, but upon some reading and reflection, it is where it should be without power mods. I think i was expecting miracles with the longer barrel. Ok, stay tuned ill have this sucker shooting 470 in short order, i know what to do now.

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PostPosted: Wed Dec 01, 2021 10:38 pm 
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Location: Ontario, Canada
Is that valve bleeding off all your power (bleed hole)?


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PostPosted: Thu Dec 02, 2021 12:23 am 
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Dukemeister wrote:
Hi thanks for the links and advice. I had a kind of knee jerk disappointment, but upon some reading and reflection, it is where it should be without power mods. I think i was expecting miracles with the longer barrel. Ok, stay tuned ill have this sucker shooting 470 in short order, i know what to do now.
you have to be real careful with 2289‘s
and the mods. They can get very powerful quickly. mine has the full Monty and in the end I detuned it as it could do mid-650s. I’m only shooting in my basement that’s too much power and noise etc and pal rated.
which pumper main tube are you using?

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PostPosted: Thu Dec 02, 2021 12:57 am 
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Did you plug the bleed hole? Also check the transfer port seal.

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PostPosted: Thu Dec 02, 2021 2:33 pm 
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TriggerHappy416 wrote:
Did you plug the bleed hole? Also check the transfer port seal.

No, I had not plugged the bleeding bleed hole! total seniors moment. I plugged it with 1 4-40 setscrew locktited in. 10 pumps.... 470 fps as expected. Happy Happy.
The nose of the valve already looked like it had been flattened so I didn't touch it, The only other mod I think I'll do for power is a long nose probe, but I have to figure out how to do it at home with a drill and drill press - no lathe at home.


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PostPosted: Thu Dec 02, 2021 2:44 pm 
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The flattened nose on the valve intake and the large intake port are also methods of detuning the gun. They create more head space

For lathe turning on my drill press, I had taken a drill chuck, a 10mm bolt and some strategically stacked washers, and bolted the chuck to the platform. I use bubble levels and squares to set it up. A 1/4" rod to get the 2 chucks lined up.
Put the work in the drill chuck and use the platform as your tailstock.


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PostPosted: Thu Dec 02, 2021 3:21 pm 
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Side pressure on the drill press spindle can cause trouble with accurate drilling later on. Friend of mine did this
to his drill press. Made it wobble,however he was really bearing down on it with files.

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PostPosted: Thu Dec 02, 2021 3:27 pm 
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Yeah it's not ideal, but for shaping small brass and aluminum parts, it works. Used my 20 year old $100 Mastercraft drill like that for years. The spindle gets loose but there's a lash adjustment... Meh. It still drills ok if I do my part. :lol:


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PostPosted: Thu Dec 02, 2021 3:30 pm 
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I can see putting the probe in the drill press chuck and having the drill bit mounted in my vice underneath. Just have to be careful to find dead centre. But, I have read conflicting articles on the power benefits of a long nose probe. Maybe some no permanent experiments are needed first.

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PostPosted: Thu Dec 02, 2021 5:15 pm 
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Have you checked the velocity with RWS Hobbys?

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PostPosted: Thu Dec 02, 2021 5:58 pm 
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Dukemeister wrote:
I can see putting the probe in the drill press chuck and having the drill bit mounted in my vice underneath. Just have to be careful to find dead centre. But, I have read conflicting articles on the power benefits of a long nose probe. Maybe some no permanent experiments are needed first.


I have tested these guns shooting with the pellet actually covering the transfer port, and there was no notable loss in velocity vs using a standard or extended probe.... Actually that's a lie. That was with one of my mk1s.

I think the thing with extended probes, is an accuracy mod, depending on the leade of the rifling. Push the pellet a little further to get the skirt to engage the rifling.
The way my brain works, it's telling me that an ideally designed chamber in a compressed air rifle, you would want the pellet as close to the port as possible. Eliminate as much excess volume as possible between the poppet and the pellet.
I could be entirely wrong.
I'm sure there is test data available on the subject.


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