Reseal of Crosman Model 1 (2280) Rifle



Author Topic: Reseal of Crosman Model 1 (2280) Rifle  (Read 131 times))

Offline DMperfection101

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Reseal of Crosman Model 1 (2280) Rifle
« on: January 09, 2019, 10:28:27 AM »
Looking for some guidance/assistance on an issue I have after resealing my Model 1 pumper.

When I did the seal job, I noticed something different in the operation of pumping to pressurize. Before the seal job, when I pumped the rifle without cocking, it would immediately begin to pressurize. After the seal job, if I pump the rifle before cocking, air doesn't pressurize; it sounds like air passes right through the rifle. However,  if I cock first, air pressurizes without any problem.

I broke down the rifle again to double check work, put back together and it seemed normal on a couple of cycles of pumping, cocking, and release. However, when I went back to the rifle a few weeks later, it wouldn't pressurize before cocking again.

I videoed the problem for posting to YouTube, but unfortunately, I can't post link here, yet.

Any suggestions for guidance would be appreciated.
  • Azusa, CA, USA

Offline DanD

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Re: Reseal of Crosman Model 1 (2280) Rifle
« Reply #1 on: January 09, 2019, 11:01:20 AM »
... if I pump the rifle before cocking, air doesn't pressurize; it sounds like air passes right through the rifle. However,  if I cock first, air pressurizes without any problem....
Hi Hector,
This happens when the hammer spring overpowers the valve spring. The resting hammer puts pressure on the exhaust valve, holding the valve open. When you cock the gun, the hammer no longer pushes on the valve stem, and the valve spring can hold the exhaust valve closed. IMO, it isn't a problem if your gun makes full power and holds air- just cock it before pumping. I have a few vintage pumpers that behave this way.
Did you replace or modify the valve spring or hammer spring when you rebuilt it?
Have fun!
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Offline BrushPopper

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Re: Reseal of Crosman Model 1 (2280) Rifle
« Reply #2 on: January 09, 2019, 11:11:13 AM »
Sounds like the new outlet seal is still forming to the seat.
The hammer spring is probably pushing the seal open.

Id try storing it under pressure for a few hours. Worst case, youll have to cock it before you can charge/shoot it
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Offline DMperfection101

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Re: Reseal of Crosman Model 1 (2280) Rifle
« Reply #3 on: January 09, 2019, 12:27:05 PM »
Did you replace or modify the valve spring or hammer spring when you rebuilt it?

Yes, the kit came with a new valve spring; therefore, I'd think that spring would be a little stronger. This gives me some direction. I'll double check both valve spring and hammer spring. I have the old parts and I'll check lengths as well. Maybe the the new valve spring was slight shorter or somehow smaller. Thanks.
  • Azusa, CA, USA

Offline DMperfection101

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Re: Reseal of Crosman Model 1 (2280) Rifle
« Reply #4 on: January 09, 2019, 12:32:18 PM »
Sounds like the new outlet seal is still forming to the seat.
The hammer spring is probably pushing the seal open.

Id try storing it under pressure for a few hours. Worst case, youll have to cock it before you can charge/shoot it

I'm going through for a triple check and will also try charging and letting it sit for a couple of hours, then check of there is a difference. I'll try the charge and store first before I dissemble again. I'll do one step at a time so that I can try to isolate is causing this. Otherwise, it charges and shots beautifully. Thanks.
  • Azusa, CA, USA

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