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PostPosted: Sat Jul 25, 2020 4:01 pm 
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Joined: Tue Dec 30, 2008 1:09 am
Posts: 10
My non-PAL Crosman Optimus shoots anywhere from 400-450 fps through a chrony. I'm thinking that a new breech seal and shim should do the trick to make it slightly faster and to be more consistent... I know the Crosman part number is B12-00-14, but I'm thinking that a trip to Home Depot would be more efficient than paying for shipping. Does anyone have the actual dimensions of the breech seal? Or an equivalent/compatible O-ring replacement? Same with a shim washer.

Mark


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PostPosted: Sat Jul 25, 2020 4:30 pm 
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Location: Kingston, ON
Put a shim behind the existing breach seal. I have used a variety of shim materials. One thing that works well is electrical solder wire. Coil it to approx the right size and then flatten a bit with a hammer to the right thickness, make several layers if you need to. If your breach seal is visibly torn, then this may not help. Otherwise give it a go and see if your guns shoots more consistently.

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PostPosted: Sat Jul 25, 2020 4:52 pm 
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Location: Ontario, Canada
Also try flipping the seal over. I shim with several windings of dental floss. I wrap the floss around a pencil and then slide it into the groove.


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PostPosted: Sat Jul 25, 2020 4:54 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 3580
Location: Somewheres near the Atlantic
According to Chevota,
Quote:
The breech seal can be replaced with a rubber O-ring, which is better and how most all guns do it. It takes a size AS568-109 (aka -109), or plumbing size 1/2"OD x 5/16"ID x 3/32" thick, or Crosman # CRS5177A013.


I would think the plumbing section O rings would be softer, easier to tear and need to be replaced more.

Well Crosman.ca does offer flat rathe shipping at 9.95 and free after 35$.


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PostPosted: Sat Jul 25, 2020 7:25 pm 
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Joined: Thu Oct 04, 2012 10:27 am
Posts: 1135
Location: Thunder Bay,On.
mwlcarter wrote:
My non-PAL Crosman Optimus shoots anywhere from 400-450 fps through a chrony. I'm thinking that a new breech seal and shim should do the trick to make it slightly faster and to be more consistent... I know the Crosman part number is B12-00-14, but I'm thinking that a trip to Home Depot would be more efficient than paying for shipping. Does anyone have the actual dimensions of the breech seal? Or an equivalent/compatible O-ring replacement? Same with a shim washer.

Mark



Go to any hydraulics shop in your town and ask for a Viton V75-109 o-ring...$0.56..
works great.. :D

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PostPosted: Sun Jul 26, 2020 9:49 am 
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Joined: Thu Oct 04, 2012 10:27 am
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Location: Thunder Bay,On.
here is the exact breech seal replacent for many of the Crosman break barrels...including yours...
the v90 also works...its a little harder seal if so desired...
https://www.globaloring.com/product/v75109/

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PostPosted: Tue Jul 28, 2020 2:42 pm 
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Joined: Tue Dec 30, 2008 1:09 am
Posts: 10
Thanks everyone. I tried the dental floss and flipping o Er tricks, but I actually had a reduction in fps... So I put it back to normal and it went back to 400-450. I've ordered some v75-109 orings, that should do the job.


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